Urban River Basin Enhancement Methods - FenixEduruif/FCT/RiverRehab/Rocha_Alves.pdfNew techniques for urban river rehabilitation (WP8) URBEM Deliverable 8-1 • New techniques for

New techniques for urban river rehabilitation (WP8) URBEM

Deliverable 8-1 • New techniques for urban river rehabilitation. Methodology i

Urban River Basin Enhancement Methods

New techniques for urban river rehabilitation

Methodology

Work Package 8

LNEC João Rocha Elsa Alves EVK-CT-2002-00082

June 2005

Deliverable 8.1


Deliverable 8-1 • New techniques for urban river rehabilitation. Methodology i

Research Contractor Contact Details Laboratório Nacional de Engenharia Civil Av. Brasil, 101 1700-066 Lisboa, Portugal Tel/fax +351 218443435/+351 218443016 web site www.lnec.pt © 2005 All methodologies, ideas and proposals in this document are the copyright of the URBEM project participants. These methodologies, ideas and proposals may not be used to change or improve the specification of any project to which this project relates, to modify an existing project or to initiate a new project, without first obtaining written approval from those of the URBEM participants who own the particular methodologies, ideas and proposals involved. This report is a contribution to research generally and it would be impudent for third parties to rely on it in specific application without first checking its suitability. The URBEM partner organisations accept no liability for loss or damage suffered by the client or third parties as a result of errors or inaccuracies in such third party data. Dissemination Status Public Report Authors João Soromenho Rocha, Laboratório Nacional de Engenharia Civil (LNEC), Lisbon, Portugal [email protected] Elsa Alves, Laboratório Nacional de Engenharia Civil (LNEC), Lisbon, Portugal [email protected]

URBEM New techniques for urban river rehabilitation (WP8)

ii Deliverable 8-1 • New techniques for urban river rehabilitation. Methodology

Summary In this deliverable it is presented the methodology for the application of techniques on rehabilitation of urban rivers, taking into account the information available from other Work Packages and the research on river engineering. Contributions to this document represent findings on experience gained in the analysis of case studies and on the experience of the river engineering practice on the countries of the URBEM partners. The rehabilitation of urban rivers includes the knowledge of adequate techniques, and its relations with all needed type of interventions, both before and after the implementation of techniques. The technical interventions are divided in two main groups: interventions to be practised in the drainage basin (controlling the hydrological processes) and interventions to protect maintain and improve the hydromorphological conditions in stream channels (controlling the hydraulic processes in bed and banks). The other associated deliverable 8.2 consists on a set of documents, namely, recommendations, specifications and guidelines. In the description of methodology there are remissions do that deliverable and also other deliverables of URBEM project, guiding the application of techniques to other aspects of the urban river rehabilitation.


Deliverable 8-1 • New techniques for urban river rehabilitation. Methodology iii

Contents 1. Introduction.......................................................................................................... 1 2. Initiative for urban river rehabilitation................................................................... 5

2.1 Initiative in case studies ............................................................................... 5 2.2 Methodology for the initiative in urban river rehabilitation............................. 6

3. Site definition in urban river rehabilitation............................................................ 9 3.1 Site definition in case studies ....................................................................... 9 3.2 Methodology for site definition in urban river rehabilitation......................... 10

3.2.1 Two ways for site definition ................................................................. 10 3.2.2 Site definition for urban river rehabilitation .......................................... 11 3.2.3 Site definition for urban rehabilitation including its associate river ...... 13

4. Formulation of river rehabilitation ...................................................................... 15 4.1 Introduction ................................................................................................ 15 4.2 Assess baseline condition in urban river rehabilitation ............................... 16 4.3 Set objectives............................................................................................. 17 4.4 Set boundaries ........................................................................................... 19 4.5 Identify controlling factors........................................................................... 23

5. Development of options..................................................................................... 31 5.1 Introduction ................................................................................................ 31 5.2 Identify options ........................................................................................... 31 5.3 Describe the consequences of options....................................................... 37 5.4 Score and choose options.......................................................................... 40

6. Monitoring of rehabilitated urban river ............................................................... 41 6.1 Introduction ................................................................................................ 41 6.2 Decide what to monitor............................................................................... 41 6.3 Design monitoring programme ................................................................... 44 6.4 Implement option and monitoring ............................................................... 48 6.5 Review monitoring results .......................................................................... 48

References ............................................................................................................... 50 ANNEX 1 .................................................................................................................. 51


iv Deliverable 8-1 • New techniques for urban river rehabilitation. Methodology


Deliverable 8-1 • New techniques for urban river rehabilitation. Methodology 1

1. Introduction One of the specific technical and scientific objectives of the URBEM research project is "to develop innovative urban watercourse rehabilitation techniques for use in future schemes". This objective is covered by Work Package 8 - New techniques for urban river rehabilitation (WP8). The deliverable 8.1 presents the methodology to adopt sound techniques for urban river rehabilitation. The techniques for urban river rehabilitation may be applied to the drainage basin (controlling the hydrological processes) and to protect, maintain and improve the hydromorphological conditions in stream channels (controlling the hydraulic processes in bed and banks). There are different types of techniques in both groups. However, the application of techniques shall be done in a harmonized procedure where beside the technique implementation; other aspects of river rehabilitation are taken into consideration. Consequently, the proposed methodology considers the tool developed to assess the potential for urban watercourse rehabilitation (Work Package 5), the implementation and review of the assessment tool (Work Package 6), the decision support methodologies (Work Package 9) and finally the development of indicators of success (Work Package 10). A great importance was done to the result of the work done for the Work Package 2, existing case studies, providing a base for the choice of the techniques and for the understanding of relative success of different techniques. The reflexions on the behaviour of different techniques and the conceptual research developed in the project had done the opportunity to define the proposed methodology. In a minor way it is also incorporate the work developed in the study-site monitoring (Work Package 3) and aesthetic evaluation (Work Package 4). The deliverable 8.2 complement the present deliverable. The deliverable 8.2 is a set of recommendations, specifications and guidelines. The recommendations on how to naturalise flow regimes is the first work document prepared in WP8. Information from Work Package 2 - Existing Case Studies, was used to define current methods for re-naturalising watercourse flow. The recommendations are divided into 5 chapters, namely, Characterisation of flow regimes, Modifications of flow regimes in urban areas, Water Framework Directive and flow regimes, Procedures for re-naturalising flow regimes and Recommendations on how to re-naturalise flow regimes. The procedures for re-naturalising flow regimes in urban rivers are divided in two main groups: measures to be practised in the drainage basin (controlling the hydrological processes) and measures to protect, maintain and improve the hydromorphological conditions in stream channels (controlling the hydraulic processes in bed and banks). The two groups are divided in six types of measures.


2 Deliverable 8-1 • New techniques for urban river rehabilitation. Methodology

All types of measures may be applied in each case, depending on the modifications the urbanisation has imposed. Only measures for river basin are to be used when the river channel did not suffer significant modifications. Rarer is the case where there are no modifications in the river basin; this may happen when an urban area is situated near a large river, where only the interventions on river channel are done, and the urban area is a small percentage of the entire river basin area. In this case only measures on river channel and banks are needed. The general situation is to apply both types of measures. The recommendations to re-naturalise the flow regimes in urban rivers include the assessment of the present situation and of the previous situation of the flow regime, before the intervention on river basin/channel; the comparison of both situations in order to obtain the synthesis of the modifications imposed by the presence of urban areas in the river basin; the choice of the measures to be designed for the river basin or/and river channels and banks; the Implementation of measures and the definition of a monitoring plan if considered necessary for the follow-up of the re-naturalisation. The recommendation on incorporation of wetlands, floodplains and sustainable drainage methods into urban schemes is the second work document prepared in WP8. The recommendations are divided into 5 chapters, namely, Wetlands in rivers, Characterisation of floodplains in rivers, Influence of urban drainage systems on rivers, Procedures to define urban schemes near rivers and Recommendations on incorporation of wetlands, floodplains and sustainable drainage methods into urban schemes. Presently, wetlands in urban areas may serve for flood control, for water quality issues and for recreation and wildlife purposes. Within the river rehabilitation concept, retention facilities close to residential and commercial areas are used as parks, playgrounds and artificial wetlands. One important percentage of wetlands is generally associated with floodplains. Many cities have grown on floodplains and urban planning has to account for potential inundations, as flooding is part of the natural hydrological cycle. Design of flood control measures often base on a 100-year event, but it is more and more understood that however large the design capacity is, catastrophic events may overwhelm this magnitude or technical measure may fail. Flood damage reduction rather than flood protection is a more realistic goal for urban areas. Considering the remaining risk even when sound structural measures are present there is always necessary to develop emergency measures and catastrophe management. The design of sustainable urban drainage facilities is not primarily a technical problem but more of an institutional concern, basically the cooperation between different departments in a city’s administration. City administration tends to follow well established principles of clear responsibility boundaries. The nature of urban drainage normally requires joint ownership and operation. This often necessitates interdepartmental cooperation in city councils in areas were often no well established



lines of communication and assignment of responsibilities exist. The choice of SUD measures is highly dependent on political and public support. Other crucial factors in most installations are land availability, types of pollutants to be removed, groundwater levels, soil types, construction costs, maintenance costs and desired pollutant removal. The specifications of new materials and techniques are mainly dedicated to the interventions on the rivers itself, namely to improve instream morphology (by classical river engineering and by soil bio-engineering), to interventions in drainage basin or to protect the flood in the river valleys. The design of sustainable urban drainage facilities, and the interventions in drainage basin, is not primarily a technical problem but more of an institutional concern, basically the cooperation between different departments in a city’s administration. However, it is included in the specifications. The specifications are prepared for three main domains related to the rivers: the instream interventions, the river valley interventions and drainage basin interventions. The first are also divided in two types of interventions: the classical river engineering and the soil-bioengineering. Considering that division of interventions they are prepared two specifications documents, each one for one of the types previously defined. The Specifications 8.1 deals with the river engineering, using classical methods of intervention, although taking into account the specific case of urban river rehabilitation. The Specifications 8.2 deals with soil-bioengineering instream interventions.



2. Initiative for urban river rehabilitation 2.1 Initiative in case studies In the Work Package 2, Existing case studies, it was presented how the urban river rehabilitation case studies were started. The most used initiatives are from public administrative institutions, almost 90 % of the cases. The fact the river are, in general, administered by public institutions shall be the major reason to find that. In second place the initiative is coming from civic stakeholders. It is thought a significant percentage of civic stakeholders are in certain way in relation with public institutions. The two major type of initiators of urban river rehabilitations have in general a technical staff, where the perception of the techniques to be used are known. The other two explicit types of initiators are the interest groups and the need to respond to legal demands. In those two types it is less probable to find technical staff to take into consideration the technical aspects by itself. It also important to know the reasons to initiate urban river rehabilitation. The same Work Package shows the major objective to the urban river rehabilitations is the ecological improvement, almost 100% of cases. However, the term ecological shall be considered in an extended way, as it is explained later. The second two objectives are the amenity/recreation and urban recreation. Both are urban driven objectives, being the first one a river driven objective. At a relative low distance appears flood control as an objective. In this case there is a joint river and urban driven objective. The last objectives to initiate urban river rehabilitations are the public involvement, visual improvement and education. Al three are social driven. The term ecological is, in certain way, related to the terminology of the EU Water Framework Directive (WFD). Indeed, all subdivisions considered in the analysis of objectives for the ecological improvement use concepts defined in the in the WFD. The most named objective is the stream morphology, 50 % of cases. The second objective is the water quality. The following objectives are related with the first one: hydrology/hydraulics, continuum and lateral connectivity. The last two objectives are the target species and the vegetation. Both are directly related with last of the three components defined in the WFD, the ecology. It is remarkable that the objectives are in very evident ranking, first in the hydromorphology component, next the water quality and finally, the ecology.



2.2 Methodology for the initiative in urban river r ehabilitation It is clear there are two main reasons to initiate a new urban river rehabilitation process: to rehabilitate a river that it is in a bad condition, referred to the transformations its channel, its water or its habitats had suffer during the urbanisation process, or to rehabilitate the urban area around the river, referred to the historical evolution of the urban occupation. These two types of reasons are completely different, departing from different rationales, although there are some common parts in the rehabilitation processes. In the proposed methodology there is a strong emphasis in the first type of reasons, the rehabilitation of the river itself. Of course, the rehabilitation of the river demands an intervention on urban aspects, but they may appear as a need, and as a consequence, and not as a point of start. It is the rehabilitation of the river that forces the use of the appropriate techniques to deal with river channel, river banks and river basin, in general. On contrary, when the reason is to do an intervention in the urban area, contemplating the river passing in that area, the river rehabilitation is a consequence, and in that condition, the rehabilitation in the river is only to obtain a better urban area. Of course, the hydromorphological, water quality and ecological aspects shall be taken into consideration, but they tend to be considered secondary objectives, unless they are included members in the team that deal in an adequate way the technical considerations for the river features. It is proposed the initiative to rehabilitate urban rivers, independently of the main reason to do that, shall include the scope inserted in the EU Water Framework Directive (WFD). The instream interventions to improve the morphology of river in urban rivers, the water quality and the ecological conditions of rivers within Europe shall comply with the WFD. In this it is expected, but for that purposes it is also needed, to have the appropriate hydromorphology of the river, river bed and river banks. This is applicable either in natural rivers or in “Heavily Modified Rivers”. The last case is present in almost cases in the urban rivers subjected to rehabilitation. When the initiative for river rehabilitation is done by the River Basin Administration is natural the process considers all aspects defined in WFD. When the initiative for river rehabilitation is done by Urban Administrations shall be made contacts with the River Basin Administration in order to guarantee the process also includes the WFD scope. According to WFD one of the main objectives of the instream interventions is to achieve good ecological conditions by combining water resources management and city planning, hence improving the quality of life. The interventions shall be done with



the “best practicable technology” and the present methodology is made to guide cities how to achieve good ecological potential in its urban rivers. The rehabilitation of urban rivers shall result of a planning process that may start a few years leading to the implementation of measures involving stakeholders that define goals and objectives and setting quantifiable targets that can be monitored.



3. Site definition in urban river rehabilitation 3.1 Site definition in case studies Site definition within case studies has displayed as well subjective approaches as methodological approaches. In the majority of case studies, about 70 %, the sites were defined with existing knowledge, no selection method being applied. In remaining case studies the site definition is based in a selection method. But these definitions have been determined by three different specific and complementary reasons: city wide, river network based or basin wide assessments. Again, the site definition, as the initiative, is commanded or by city administration or by river administration (network or basin). The methods used to assess (potential) rehabilitation were the following (Table 7 in deliverable of Work Package 2):

• Area wide assessments of water body state (including in landscape planning, water body development plans, territorial development programmes, landscape assessments);

• Impact analysis and assessments; • Ecological studies analysing restoration potential; • Pilot projects/on-site tests; • Site visits and assessment of the knowledge of stakeholders.

The aspects covered were the following:

• Significance of reducing water pollution; • Potential for ecologic rehabilitation, e.g. re-colonisation; • Significance of social/aesthetic/cultural/economic enhancement • Potential to reduce flood damage • Site ownership and boundary lines.

It is noteworthy the aspects covered did not included explicitly the largest type of intervention, in the river morphology, although it may appears in the reduction of flood damage aspect. The space and time scales are also important characteristics to be taken into consideration in the site definition. In the case studies they were analysed the width and length of the rehabilitated sections. The largest ranges of width were 1-5 m (stream) and 5-25 m (small river), both with 30% of cases; the third range was less than 1 m width (streamlet) in 23% of cases; the range 25-100 m (large river) had 9% of cases, and finally in 4% of cases the range was 100-300 m (major river). In 4% of cases no information was available.



The lengths of rehabilitated sections of water courses showed also a wide range: the largest ranges of length were 101-500 m and 1-2 km m, both with 22% of cases; the third and fourth ranges were 2-3 km and larger than 3 km, in 17% of cases; the range 0.5-1.0 km had 9% of cases, and finally in 9% of cases the range was less 100 m. The mean length was about 2000 m. According to the authors of the Work Package 2 deliverable, the emphasis of the survey to primarily consider complex rehabilitation approaches with “good practice” character, larger scheme may prevail. In fact, it can be assumed that a much higher proportion of spatially restricted schemes may be found in European cities. According to the deliverable of Work Package 2, “rehabilitation projects range in scale from incorporating an entire drainage basin down to single interventions along very short reaches of water courses. Urban river rehabilitation projects very often are combined with a general upgrading of the more or less close surrounding of the water course itself. Not seldom the schemes comprise the landscaping of the adjacent land, the establishment of new paths or facilities for information. For this reason the land areas affected by rehabilitation projects also differ in size but without close relation to the size of water course addressed”. The average duration from initiation to implementation of a scheme took between 6 to 8 years, varying from a few months up to about two decades. Implementation duration averaged 2.9 years, varying from a few weeks to 15 years. Longer time periods usually were connected to basin wide or citywide programmes, while shorter time periods related to less complex, site related projects. 3.2 Methodology for site definition in urban river rehabilitation 3.2.1 Two ways for site definition The site definition is made by two different main processes, in relation with main scope of the intervention, and by consequence, the technical aspects of river rehabilitation. One of the main processes is centred in the river itself, although some urban aspects are necessarily included. In this process the driving forces are in the River Basin Administration or equivalent institutions. The main scope is to rehabilitate the river, situated in an urban area, taking into consideration the target a better river, and by consequence also a better urban in the adjacent area, banks and flood valleys. In this case, it is natural to find an emphasis on the river techniques. A joint work to city administration is needed. The other main process is centred in the urban rehabilitation near an existing bad river. Of course, the river aspects are also necessarily included, but in a certain way more as an urban solver. In this process the driving forces are in the Urban



Administration or equivalent institutions. The main scope is to rehabilitate the city, situated near a river, taking into consideration the target a better city, and by consequence also a better river passing there, with its banks and flood valleys saw as urban zones. In this case, it is natural to find an emphasis on the urban techniques. A joint work to River Basin administration is needed. The site definition for these two main processes is not the same, although some aspects are necessarily present in both. 3.2.2 Site definition for urban river rehabilitation When the rehabilitation of an urban river is initiated is needed to define the river reach. There are not rigid rules to define the site where the rehabilitation is to be implemented. However, using the WFD terminology is possible to define simple criteria to define the site where the rehabilitation is to be done. Considering the type and intensity of efforts to be used in the rehabilitation it is possible to divide the type of intervention, and consequently the site definition. The first basic distinction is the

1) Instream river rehabilitation; 2) River basin rehabilitation (including or not the instream).

The instream river rehabilitation is concentrated in the main channel, and its lateral adjacent zones where the flood pass. The site definition contemplates, at least, the definition of the downstream and upstream cross sections. This is relatively straightforward but only an expert in flow regimes can find the appropriate cross sections to tackle with the hydraulic aspects. The definition of the adjacent areas, equivalent to the flood prone area, is relatively more difficult, being advisable to use a step by step approach, unless previous data gives directly the right definition. An accurate definition is cost and time consuming. At a first guess a rough definition may be done with the analysis of geomorphology and geology maps, or with the help of the inhabitants knowing the history of past river floods, or analysing probable flood marks. The other more accurate definitions for the flood prone area will be done based in hydraulic modelling of present, past or future situations. The hydraulic modelling needs good river data to guarantee reliable results. The calibration and validation of hydraulic modelling shall be imposed because is the only way to be successful in the proposed river rehabilitation. For hydraulic modelling is needed to define the contributing river basin. That definition is only to determine the river discharge to be used in the computation. In



some cases the river basin is entirely outside the urban area, in other cases the contrary may be found, all area is in the urban area. These two limiting cases are quite different in the implications the study may have. The last case may generate a chain of scenarios for the reciprocal influence of river basin and instream. The river basin definition is relatively simple on the conceptual point of view, it is to determine the river basin boundaries, where the river processes are generated and transported to the river channel. Indeed, the river basin, a spatial area where complex physical, chemical and biologic processes are generated and transmitted downstream, may also be viewed as a network of small streams going from the river basin boundaries downstream to the lower cross section where the river basin is defined. The next distinction in the site definition is related with the type of intervention in the instream rehabilitation. Following also the WFD terminology, and from a soft to a hard intervention they may be defined three levels of urban river rehabilitation:

a) Biological; b) Water quality; c) Hydromorphological.

In a strictly sense they shall be viewed as a forced set of three aspects of an unique intervention, but in practical terms, the two first types of interventions may be used without any physical (hydromorphological) intervention. In more complex river rehabilitations it is necessary to have heavy hydromorphological interventions as a base for better water quality and biological interventions. Also, some times there is only one type of intervention. So the consideration of the three proposed levels of instream river rehabilitation to define the site is quite useful. For each level the definition of the site have some particular features. Considering again the WFD terminology, and also the rationale considered in that Directive, the base level of intervention is the hydromorphological, an element supporting the biological elements. The definition of the site shall include the three basic hydromorphological elements: the hydrological regime (quantity and dynamics of water flow and connection to groundwater bodies), the river continuity and the morphological conditions (river depth and width variation, structure and substrate of the river bed and structure of the riparian zone). Consequently for the site definition it will be necessary to gather all pertinent data related with the above to mentioned elements. From the beginning, first in a very simple way, the site definition shall consider those hydromorphological elements. For the definition of the boundaries of the site (upstream and downstream river cross sections) all those elements are needed. As each element has different types of control and influence they will be found different cross sections. Some times the hydraulic control will be dominant, imposing larger distances for those cross sections, other times the river bed structure are dominant, and so on. Consequently it



is not easy to find general and simple criteria to help find the border cross sections for the site. This is the reason to propose the site definition by a hydraulic expert. The same type of considerations is valid for the chemical and physico-chemical elements supporting the biological elements and for the biological elements. The chemical and physico-chemical elements include a list of parameters (general and specific pollutants) and consequently, in order to consider different types of influence and its evolution along the river, it may imply different cross section localisations for the borders of the site, either in the river itself, either in the main affluents to the river. The biological elements include the compositions and abundance of aquatic flora, benthic invertebrate fauna and fish fauna. The last element shall also consider the age structure. For each of biological element we may find different border to analyse the situation. Considering all these elements it is straightforward to conclude the site definition in the river must be done by a small team including at least to basic domains: hydraulic and biology. It is very probable that each element implies different cross section in upstream and downstream border. It is possible to assert the site definition may imply a variable geometry. This is not contrary to the fact in simple case it is enough to define only two cross sections for the border of a river reach to be subject to rehabilitation. Each of the main cross sections used as boarders of river reach to be rehabilitated defines a river basin. Some of the river basins are not urban and are not included in the rehabilitation intervention. However, others of the river basins are in the urban areas. In this case a careful definition of river basin limits shall be done, including the main sub basins inside. 3.2.3 Site definition for urban rehabilitation including its associate river When the rehabilitation of an urban area is initiated including an existing river is also needed to define the river reach. But in this case the site definition is more intensely marked by the urban scope. The definition of the river reach where the rehabilitation may occur may be influenced more by the urban site definition than by the river limit definition. Beside that, all considerations presented in 3.2.2 are applicable. In general, in urban rehabilitation a strong presence of river basin rehabilitation (including or not the instream) is present. The instream river rehabilitation, concentrated in the main channel, and its lateral adjacent zones where the flood pass, are confined strictly with urban area, unless an appropriate hydraulic approach leads to a more technical based definition.



The adjacent areas, defined as urban areas, may be quite different the flood prone areas. Some times they are larger, other times smaller ones. The river basin definition in an urban area may be complex, being the sub basins difficult to find, and the relations between surface processes and under ground networks, generating and transporting to the river channel water and diversified pollutants, not entirely identified for all areas. In most cases the river basin is entirely inside the urban area. The development of the urban areas creates pressures in river. The WFD also imposes “the collection and maintenance of information on the type of the significant anthropogenic pressures to which the surface water bodies in each river basin district are liable to be subject” (Annex II, 1.4). Among other items they are the following:

1) Estimation and identification of significant point source pollution, in particular by substances listed in Annex VIII, from urban … and other installations and activities;

2) Estimation and identification of significant diffuse source pollution, in particular by substances listed in Annex VIII, from urban … and other installations and activities;

3) Estimation and identification of significant water abstraction for urban …and other uses, including seasonal variations and total annual demand, and loss of water in distribution systems;

4) Estimation and identification of the impact of significant water flow regulation, including water transfer and diversion, on overall flow characteristics and water balances;

5) Identification of significant morphological alterations to water bodies; 6) Estimation and identification of other significant anthropogenic impacts on

the status of surface waters; 7) Estimations of land use patterns, including identification of the main urban

… areas and, where relevant, fisheries and forests. All type of above written items is needed to use in site definition. Indeed, when an urban area is rehabilitated, where a river is also or not rehabilitated, those items are needed to identify the pressure on the river reach. This river reach may not always be inside, or in front of, the urban area, because some actions related with water control may be sent, or received, from adjacent or larger distances from the urban area. The transfers to or from urban areas shall be taken into account in the definition site of rehabilitation area, river basin or river channel.



4. Formulation of river rehabilitation 4.1 Introduction In the Work Package 5 it is described the tool for assessing potential for rehabilitation. Knowing any river rehabilitation may generate a large number of options it was chosen the multi-attribute decision making to select from a range of options. Like any other problem solution in river rehabilitation the decision maker has to:

a) Set the objectives, b) Specify the criteria on which the analysis is to be based, c) Specify how the criteria on which the analysis is to be based, d) Specify the analysis method to be adopted, e) Review the results of the analysis

In addition the decision maker may also be involved in:

f) Developing different options to be assessed, g) Assessing the different options to be assessed.

The decision maker may be a single person or may be a group; it may involve some or all of the stakeholders or their representatives. Also the problem may only one, with a large complexity, or it may be, in order to facilitate the decision, disaggregated in parts, when some independency may occur. The techniques for urban river rehabilitation, the main subject in the Work Package 8, may be one part of the disaggregation. Being or not disaggregated the complex of actions, in the methodology presented they are focused the options for the techniques used in river rehabilitation. Some remarks are made when strong links are present for other subjects related with river rehabilitation, such as urban, aesthetic, economic or social ones. As pointed out in Work Package 5, the first process in the assessment of the potential for rehabilitation is the process 1a, formulation of urban river rehabilitation. This process is divided in four parts:

1) Assess baseline condition; 2) Set objectives; 3) Set boundaries; 4) Identify controlling factors.

The following sections of the methodology present these four parts of the first process applied to the techniques for urban river rehabilitation.



4.2 Assess baseline condition in urban river rehabi litation The assessment of the present condition of an urban river or, saw from a different point of view, an urban area where a river is running, may be done with different sensibilities, different perspectives, different interests, different institutions, shortly, is a large spectrum question. As posed by Work Package 5, this part may be done in two actions:

1. Review information on catchment and river, 2. Identify stakeholders.

In the Recommendations 8.1 they are characterised the flow regimes in urban areas, in the present situation and in the previous conditions, in order to assess the river condition and the potential to be rehabilitated. Considering all elements included in that Recommendations 8.1 the following three steps are recommended to formulate the urban river rehabilitation, or to consider the re-naturalisation of the flow regimes in urban rivers:

1) To assess the present situation of the flow regime. The assessment will include the river basin and the river channel and banks elements, taking into account the information described in chapters 2 and 3, and 6.2 of the Recommendations 8.1. This assessment shall take into account the elements included in the WFD, as referred to in Chapter 3 of the Methodology.

2) To assess the previous situation of the flow regime, taking into account the

information described in chapters 2 and 3, and 6.3 of Recommendations 8.1. The assessment may be done by two alternative ways; i) the real previous river regime is obtained gathering data base and historical facts and documents or ii) an ideal previous situation is obtained by comparison of neighbour unchanged river basins or by theoretical reasoning.

3) To compare both situations in order to obtain the synthesis of the

modifications imposed, during all history, by the presence of urban areas in the river basin. The list of modifications is the basis to define the interventions to be applied for the river rehabilitation.

From the knowledge of hydrological regime, the discharges for different time and space situations, it is possible to characterise the flow conditions in the river channels. The characterisation of channel flow processes should include the characterisation of bed and banks and the hydraulic structures. The only way to collect the required data is to survey the site. For important structures the design documents should be referred to, where hydraulic computations may be included.



The hydraulic computations using the available data may be relatively heavy, involving skilled human resources, appropriated models, and for good results, calibrations. It is very easy to make large errors when calibration is not done. The results of hydraulic computations are very sensitive to some input data, such as bed slope, and mainly to the roughness coefficients. There is no good method for using the right values for coefficients, unless a calibration is done or an experienced team is involved. For the alluvial rivers the difficulties are increased. The characterisation of river bed sediments should be always included. The characterisation of river flow processes should be done for the appropriate situations, being included in most cases, at least: 1) the flood events, where the river channels are small to convey all water, 2) the full bank where the beginning of flood occurs, 3) an average discharge situation, representing the more frequent situation and 4) low flow situations. For certain rivers the discharge decreases to zero, remaining, however, in most cases, sub superficial flows, and small stagnant water bodies. The computations, supported by calibrations, should deliver for the chosen cross sections, the water flow characteristics for the cases referred to above; water levels, velocities, singular flow behaviour (for instance changes of flow type, sub critical or super critical), 2D or 3D features (lateral currents, vortex). The hydraulic characterisation may advance the sediment transport and water quality characterisation, and also the biological characterisation. The degree of comprehensiveness of the hydraulic characterisation depends of the importance of the study. As the hydraulic computations are in general heavy they should be included, certainly, in large studies, but may be simplified accordingly the size of the problem. If we are dealing with a potential intervention on short reaches of small rivers it should be enough to do simple computations with a minimum of calibration procedures and light site surveys. The modifications encountered in the river channels situated in urban areas may vary from insignificant to large deviations. Similarly to the hydrological modification analysis the knowledge of the time evolution of the urban occupation is the basis for the characterisation of the previous conditions, and a reference situation shall be found. It may correspond to a situation where no urban occupation was present, or alternatively a light occupation existed. The choice is pure arbitrarily. It is evident the technical work shall be done taken into consideration the experience of all, being relevant the stakeholders, where studies may exist and personal knowledge has a precious value. 4.3 Set objectives The knowledge of the baseline condition of an urban river, or an urban area where an urban river runs, is the main base to set objectives for a potential river rehabilitation,



or urban rehabilitation, including its river. Following the same questions for the assessment, the setting of objectives will be dependent of different sensibilities, different perspectives, different interests, different institutions, having a large spectrum scope. As posed by Work Package 5, this part may be done in three actions:

1. Set broad objectives, 2. Consultation with stakeholders, 3. Set specific objectives.

In the Recommendations 8.1 they are presented, in chapter 5, the procedures for re-naturalising flow regimes in urban rivers and urban river rehabilitation. They are divided in two main groups, measures to be practised in the drainage basin (controlling the hydrological processes) and to protect, maintain and improve the hydromorphological conditions in stream channels (controlling the hydraulic processes in bed and banks). The two groups are divided in six types of measures. Both types of measures may be applied in each case, depending on the modifications the urbanisation has imposed. Only measures for river basin are to be used when the river channel did not suffer significant modifications. Rarer is the case where there are no modifications in the river basin; this may happen when an urban area is situated near a large river, where only the interventions on river channel are done, and the river basin with urban areas is a small percentage of the entire river basin area. In these cases only measures on river channel and banks are needed. The general situation is to apply both types of measures. These recommendations are complemented by the Recommendations 8.2 where wetlands, floodplains and urban drainage methods are incorporated into urban schemes. It is known the urbanisation has been narrowing the watercourses to the minimum space possible. Due to urbanisation pressure and narrowing of watercourses within a very limited space, safety fencing and supporting walls have been built, as well as other buildings that strongly reduce the hydromorphological state and influence the physical state and biological state of the river. Consequently, a broad objective in river rehabilitation shall include measures to create basic conditions for widening of the stream and management of river banks. The basic problems are issues in terms of ownership rights and water-related rights linked with the buildings. Besides providing additional space for the improvement of the hydromorphological state, by widening the channel and the banks the channel flow is enhanced and the water level locally reduced. The extended channel enables meandering, formation of pools and rapids, dunes and wetland riparian areas. Also, the channel provides for a better flow of flood waters. The influence is favourable for the ecological state of the water body in its entirety.



The extensions can be done in several variants, i.e. widening of the river bed only, or widening of banks with different approaches and modern consolidations made of natural materials. The rehabilitation may also include the reconstruction of bridges and enhancement of their scale. The improvement of instream morphology using river engineering shall be based in well sound application of river hydraulic knowledge. It is a specialised scientific domain, and when this is neglected the success of the intervention is low. If the above referred to broad technical objectives are worked by the expert in river hydraulics, a following round of stakeholders consultation is needed to refine the setting of objectives, taking into consideration not only the technical expertise, but also the diffuse knowledge of the river problems, coming from other disciplines, and the constraints imposed by the existence of urban areas. The main broad objective for the WFD is to achieve the “good ecological potential” of urban streams. Consequently, the setting of specific objectives in river rehabilitation shall also follow a more natural approach, in relation with simpler hard technical approach. In the past, many rivers were stabilised and hardened with concrete and steel in order to accommodate navigation and to protect urban uses from flooding and erosion. River shorelines were typically designed for a single purpose. Today should be followed a growing support for ecology and multiple uses as well as an interest in using “soft engineering” of shorelines at appropriate locations. Such an approach incorporates flood conveyance concerns, aquatic habitat, riparian habitat, water quality, recreation and aesthetics. The setting of specific objectives shall take into account all these aspects. 4.4 Set boundaries Following the knowledge of the baseline condition of an urban river, or an urban area where an urban river runs, and the setting of specific objectives for a potential river rehabilitation, or urban rehabilitation, including its river it is needed to set boundaries. As posed by Work Package 5, this part may be done in four actions:

1. Define spatial extent of assessment, 2. Define time-scale for assessment of plan or project, 3. Determine resources for assessment, 4. Define success indicators and acceptability criteria (initial review to

be refined during assessment. The chapter 3 of the Methodology presents the first steps to set boundaries, i.e. the site definition. In the Recommendations 8.1 they are presented, in chapter 2 and 3, respectively about characterisation of flow regimes and modification of flow regimes in urban areas, the main definitions of physical processes in rivers to help the definition of spatial and time-scale boundaries. Also the content of two chapters in



Recommendations 8.2 helps to define those boundaries. The chapter 3, about characterisation of flood plains in rivers, is related to the definition of lateral boundaries. The chapter 4, about influence of urban drainage systems on rivers, has information on the urban systems that, in a certain way, are boundaries for the river system. The definition of spatial extension of the assessment shall take into account the relative spatial scale of the river and urban areas. In Work Package 4, Deliverable 4.2, Methodology of classification of the aesthetic value of the selected urban rivers it is recognized that “river width is a geometric parameter that has a strong influence on the interrelationships between the river and the city. It influences the scale of the river corridor and the waterfront and its uses, the accessibility network, the transponibility, traffic and many other factors in the urban/watercourse environment”. Indeed, the scale and size of an urban watercourse within the urban morphology is a very important relationship. The river width has been chosen in the methodology of classification of the aesthetic values as one of the starting items for selecting the case study, due to its relevance in the urban context.

The width of a river is a good measure of the importance of a river, and is strongly correlated with many aspects of river system and river basin upstream feeding water, sediments, and other water constituents. In Recommendations 8.1, section 2.2.2 it is presented an available quantification of the river characteristics based in the order of the rivers. It was find out that order of the major part of the rivers to be rehabilitated are between fourth (IV) and ninth (IX) orders. That means with river basin areas and river lengths between about 2 km2 to 300 km2 and 2 km to 50 km. According to Recommendations 8.1 the modifications in the river net are very dependent on the space scale of the two areas, the river basin area and the urban area. Different cases can occur, and for each case different spatial extent of assessment is necessary. Case 1 – Urban area much smaller than the river basin

The consequences for river modification, during past times, are minor except on the part of catchment area where the urban area is settled. In this case, only a part of the river may be changed during the past. Definition of spatial extent is relatively simple, being necessary to separate the parts of rivers basin, respectively included in the urban area and outside.

Case 2 – Urban area covering the major part of the river basin The consequences the river may be more or less important depending where the urban area is located in the catchment. If the urban area is in the upstream part of catchment, it may significantly alter the river network in the whole catchment, not only in the urban area, but also in the downstream part. If the urban area is in the downstream part of the river network the consequences to downstream are not felt, and the urban area receives a natural river network in



the upstream border. The definition of spatial extension shall include all types of river basins accordingly with the relative importance.

Case 3 – Urban area covering the entire river basin In this case usually the river net is turned completely artificial. Indeed, the large towns may occupy more than one river basin. The spatial extension of the river basin is practically superimposed to the urban area.

As referred to above the order of major part of the rivers to be rehabilitated is between (IV) and (IX), and these orders are associated to river basin between 2 km2

to 300 km2, which are at same order of magnitude compatible with the size of urban areas. For smaller river orders the area of river basin is approaching a limit where they may be hardly identified as urban areas. For larger river orders the size of the river basin is high compared with the area of larger towns. This does not mean that urban areas are not present around larger rivers. But in this case we can hardly assert an intervention in the river as a result of the influence of the urban area, except in the case of the banks. In this case, the bank is a border, or an interface, between the urban area and a large water body. The river network may be extremely disturbed in orders I and II of the stream as a consequence of urbanisation has been destroying the natural river network. Artificial channels for mixed sewage system and storm water system are built and they quickly drain water from non-permeable urban areas. Many streams have a very limited water flow. Since artificial piping systems and culverted streams have a smaller permeability, during some flood events the roads may change into temporary streams. In consequence the definition of boundaries, either in river network either in river basin areas, is not straightforward in urban areas heavily occupied. The careful analysis of detailed maps and field survey are needed for a good setting of boundaries for river rehabilitation in urban areas. In the river environment the time scale is associated to the river size. As referred to in Recommendations 8.1, chapter 2, the hydrologic processes in a river have times depending in river basin size. For very small river basins the significant times are of order of minutes to few hours. It means the rain events and associate flow discharges are running in times of order of rain event time and its multiples. For small river basins the hydraulic events have generally times less than one day. The peaks of river discharges are sharp in a time-discharge graphic and the water level variations along time are fast. Same processes in larger river basins have a similar variation type but now considering time values increasing from hours to days as the river basin size increases. However, the presence of two extreme seasonal conditions, the wet period with large amount of rain, and dry period with absence or small amount of rain, causes the consideration of a second time scale for the analysis of the hydrologic and hydraulic



processes, the seasonal variation, and also the monthly variation of hydrologic and hydraulic parameters. The hydrologic and hydraulic processes vary also year from year. That variation shall analysed in long term time series, with monthly or daily discrimination. The river alluvial beds are moved by the successive river regimes along the years. For that particular analysis may be necessary to consider even large time scales, being possible to arrive to centuries as base for the definition of river bed trends in the past, and also for the future. The conclusion is the need to include multiple times scales to set the time boundaries of river rehabilitation. The time scales in river processes are accompanied by equivalent time scales in urban activities: from short time activities as emergency actions during dangerous flood events, to daily action in day life of a city, like garbage collection, cleaning of streets and of river banks, to seasonal actions like flora activities, to yearly action like planning, building activities and finally to average and long term activities like urban plans or trends in society. Consequently, the definition of time scales of plans and of detailed projects for river rehabilitation may be different. In comprehensive river rehabilitation projects all time scales shall be included, in order to do not forget any important subject. In small river rehabilitation projects, with some few details in river and urban parts, only one time scale may be used, as for instance in a small intervention in a cross section of a river, where is enough only instantaneous flood discharge for the project. But for the same example, if a alluvial river bed is present, it should be advisable to consider the time scale for long period analysis, such as few decades trend. If beside a physical intervention, in the hydromorphological features of a urban river, there are interventions in water quality and ecological elements of the urban river, it is needed to include year time scales, covering the daily river discharge variations along the year, or years, because both river processes are very sensitive to river discharge variations and also to the variation of climate parameters (temperature, radiation) along the year. After the definition of spatial and tome boundaries it is possible determine the resources for the assessment and formulation of river rehabilitation. For smaller space scale and longer time scales the needed resources shall be larger. It may be noted that for different time scales are, in general, associated different expertises in the analysis of river problems, multi disciplinary teams shall be used. In the proposed methodology the definition of success indicators and acceptability criteria (initial review to be refined during assessment) shall be included in the next part of the formulation of river rehabilitation.



4.5 Identify controlling factors Following the previous parts, assess baseline condition, set objectives and set boundaries, there is a last part in the formulation of river rehabilitation, of an urban river, or an urban area where an urban river runs, identify controlling factors. As posed by Work Package 5, this part may be done in five actions:

1. Check legislative requirements, 2. Determine financial limits, 3. Check relevant strategies and plans (including flooding, land use

planning, environmental, etc.), 4. Identify stakeholder requirements (including public), 5. Identify physical constraints.

As already referred to in the proposed methodology it is included an action coming from the previous part:

6. Definition of success indicators and acceptability criteria (initial review to be refined during assessment).

The actions 1, 2 and 4 are not directly related to the techniques for the river rehabilitation. However, all three have an indirect link with the techniques, mainly the second, imposing cost limits imposes also limits to the type of solutions. The stakeholder requirements may also impose some limits to the type of solutions. The actions 3, 5 and 6 are associated to the technical formulation of river rehabilitation in urban areas. For the point of view of technical intervention in river rehabilitation the kernel questions are in the action 3, to provide the relevant strategies. Side by side the technical team and other discipline teams shall raise the potential strategies, taking into consideration the legislative requirements, the financial limits and the stakeholder requirements. In the Recommendations 8.1 they are presented, in chapter 5, procedures for re-naturalising flow regimes, the planning procedures and the measures to be practised throughout the river basin and for urban stream rehabilitation in channel bed and banks. Also the content of chapter 5, in Recommendations 8.2, procedures to design urban schemes near rivers, is a base to encounter the relevant strategy or the best plan of river rehabilitation. The main technical strategies for the urban river rehabilitation, or for urban rehabilitation including a river, are, as already presented in 3.2.2 and 3.2.3, the intervention in one or more than one level, considering the rationale of the WFD:

a) Hydromorphological, b) Water quality; c) Biological.



Also the intervention may be done in one or more of the following situation: 1) Instream river rehabilitation; 2) River basin rehabilitation 3) Urban area rehabilitation with some or all components of passing rivers.

The strategies to be checked shall including the appropriate isolated or combined types of intervention to rehabilitate river and urban areas together. The next fundamental question is about the target for the river rehabilitation. There is the intention to renaturalise just as the river was before the urbanisation? In Europe this means there is the intention to recover centuries of history. Only in rare cases this is an attainable target. The most common case is to restore some aspects of the previous river environment. The main scope of the strategies of river rehabilitation shall be to obtain good combinations of interventions to restore as much as possible the “natural” conditions of the river. The “natural” conditions are very difficult to define. A relative broad set of conditions are possible, turning this fuzzy concept. Consequently, even in a team of river experts there will raise different targets, and by this reason it is easily found different parallel strategies. The combination of strategies for the river itself and other strategies of urban rehabilitation, when that exists, leads to a great number of set of interventions. In Work Package 5 the Process 1b, defining method of assessment, helps to tackle this problem. It is important to remark it is possible to consider an extension of the target “natural” conditions, in the sense of identical to the original conditions; to the target “natural” conditions with the sense of conditions where the natural forces and processes are used to “create” a river environment like natural, but where the controlling of processes is not identical as the original one. We call this river rehabilitation more as “river creation”. When this process is not scientifically sound there will be problems to solve in the future, because they will be needed additional interventions to maintain the design “created” river. The problems may arise easily in the morphological interventions and in the ecological interventions. The corrections for the first one tend to be costly, compared to the second one. Relatively the interventions in the water quality are easily done and with lesser doubts in the results, although they can have higher costs compared with other two. The physical constraints shall be identified. There are different types of physical constraints, some associated to the river channel (like minimum or maximum permissible hydraulic parameters, singularities on the river bed, water quality standards compliance, ecological maintenance, etc.) or river basin (permission on or not of water transfers, maintenance or not of some land cover, etc.) other with urban features (historical buildings or infra-structures, administrative subjects, social status, etc.). Some of the constraints are self evident, but others are only known by expertise. This leads to discussion because they do not seem constraints for some in opposition to others. Again the identification of constraints is a multi disciplinary work,



and the final list of constraint is not a straightforward task, but an iterative task, implying some consultation outside the teams. Finally, there is the last action of the Process part 1a – Identifying Controlling Factors, to define (success) indicators and acceptability criteria. It is admitted it is iterative action, with an initial review to be refined during assessment. In Work Packages 3, 4, 5, and 10, they are proposed parameters to, in a complementary way, identify controlling factors. The four lists have similar characteristics, but they are also different in the way of presentation, and in different amount. The lists are presented in the Annex 1. All except the Work Package 4 are based, in a certain way, in the WFD, for the case of the ecological parameters. The terminology for parameters is different. The term parameter is used in WP5 and WP8, the term data is used in WP3, the term indicator is used in WP4 and WP10 and The terms objective and attribute are used in WP5. The amount of parameters are also quite different, from 38 to 99, compared to 15 for the WFD, although these are incomplete for the purpose of URBEM, being also needed for social and economy identification beside the ecological one. For the methodology for the techniques of urban river rehabilitation the dominant parameters are ecological, including the hydromorphological, chemical and physico-chemical and biological. However, a few socio and economic parameters shall be taken into consideration. The WP3 uses the lowest number of data, 38, being divided by 9 hydromorphological, 9 chemical and physico-chemical, 1 biological and 19 socio- economic. The WP4 increases the number of indicators to 52, being divided by 14 for the river (5 hydromorphological, 4 biological and 2 on risks), 19 for the city (including 1 for pollution) and 19 for people (7 for river, 4 for city and 8 personnel). The WP5 increases again the number of parameters to 72, being divided by 32 for WFD, 32 for the aesthetic (17 for river and 15 for city), 10 for social and 2 for economic. The WP10 increases again the number of indicators to 99, being divided by 43 ecological, 43 social, 8 economic and 5 site specific. It is evident the possibility to increase as much it is possible the number of parameters, but this is inconvenient for the treatment of data. Indeed, the WFD only needs 15 parameters divided by 5 hydromorphological, 7 chemical and physico-chemical, and 3 biological.



As referred to before for the techniques for urban river rehabilitation the dominant parameters are those related with the WFD system. The reasons to arrive to comparative large numbers of parameters are the redundancy (unnecessary), the disaggregation (excessive) and needs to include specific thematic parameters. Departing from the base, the hydromorphological parameters, it is followed the description inserted in Table A1.2 in Annex 1, to describe the fundamental parameters to be considered in the techniques for urban river rehabilitation. The parameters are designated by T (technique) and H (hydromorphological), C (chemical) or B (biological) and by a number in sequence. The first 2 parameters TH1 to TH2 are related with the Hydrological regime (quantity and dynamic of water flow). The main two parameters are river discharge and river slope . They represent the two dominant driving forces: the amount of water running in the system and the gravitational forces moving the water. It is known to compute river discharge is needed other parameters but they do not need to be explicit, like rainfall, basin area, topography, concentration time, etc. The simpler way is to use only two parameters TH1 as Q, and TH2 as S. However, for some rehabilitation projects is convenient to split Q in two or three Qi, for design discharge (for instance, 100 year return period, Q100) or average discharge (Qave) or dry season discharge (Qmin). Also, S may be splited in more than one characteristic slope of the system. In total it may be necessary two to six parameters, TH1A to TH1C and TH2A to TH2C. The letters following the number designate parameters in a series of the same kind parameters. In WP4 they are used the R1 and R2, and in WP10 the indicators 14, 15, 33. It is also noted the parameter for floods are mainly inserted in socio-economic subject. Although the perception and the damages of floods are such that, it is important do not skip the main and first step of flood analysis, to know the flood discharge and the consequent flood depth, flood velocity, and flooded area, before arrive to its consequences. In WP4 there are the indicators R13 and P4, and in WP10 the indicators 34 and S20. The connection to groundwater bodies may be represented only by one parameter TH3, subterranean discharge from or to river Qsub. In WP10 they are used the indicators 16, 36 and 37. The river continuity may be characterised by the presence or absence of obstacles, like straightening, weirs, bridges, blocks, rock formations, and so on. It is difficult to define a consistent numerical parameter, but maybe the head loss associated to that is a good solution. It is proposed the TH4, head loss , ∆H.



In WP4 there is the indicator R8 and in WP10 the indicator 17 and 39 (repeated?). The morphological conditions of the river to be rehabilitated need to be characterised in the minimum by four parameters: TH5, river depth (H), TH6, river width (B), structure of river bed, TH7, median grain size of aluvionar bed (D50) and structure of riparian zone, TH8, median grain size of aluvionar bank (Db50). The morphological conditions are function of space and time. Consequently the measures of the above parameters shall be done in time series data. The time may be also separated in pre and post intervention, as a lot of parameters described here. It is also noted the depth is associated to a discharge, although not in a unique way. The cross-sections shall also be known by draws, or in a digital terrain model, that is in a 3D format. This set of parameters, the cross sections , is designated TH9, Z(x,y). In WP4 the indicator is R3 (only width), but also R4, R6 and R7 are morphological indicators. In WP10 there is the indicator 18, and maybe repeated the 42 and 43. In WP3 and WP5 there are references to the bank or bed material. An additional two parameters important to analyse the hydromorphological conditions, and not included in the WFD, are the TH10, sediment yield of the river basin (Ps) and TH11, sediment transport capacity of the river (Qs). Both are needed to determine the sediment balance in the river, and consequently to quantify the state of aggradation or degradation of alluvial river bed. The same analysis may be done comparing the time evolution of the cross sections. The sediment transport shall be also divided in two main fractions: the transport of coarser grains are more relevant for the morphological condition of the river than the transport of finer grains, passing the cross sections without any interference in the river bed, unless a siltation process occurs. So they are proposed the parameters TH11A, bed load discharge (Qsb) and TH11B, suspended load (Qss), wherever they are needed. Only in WP10 there is an indicator related to the sediment transport, the 48, siltation. Also in WP10 there are two indicators aggregating the morphological conditions, 8 and 9. They are respectively the morphological quality and hydromorphological conditions, a little bit conflicting each other. The next set of parameters is related to the chemical and physico-chemical water quality, indicator 7 in WP10. In the techniques for the rehabilitation it is enough to consider the aggregate format as it is included in the WFD. Indeed, the quality of water depends in a large amount of physical and chemical parameters, but for the present purpose the fine disaggregation of parameters is not needed. They are taken only seven parameters such as is written in WFD. They are TC1, thermal conditions (T), TC2, oxygenation conditions (O), TC3, salinity (Sa), TC4,



acidification status (pH) and TC5, nutrient conditions (N) for the general pollution and TC6, pollution by priority substances (Pps) and TC7, pollution by other significant substances (Pss). In WP3 and WP5 they are indicated the data and parameters covering the same set of chemical properties, relatively more disaggregated in WP5. For instance the nutrient status shall be determined by the presence of NH4, NO3, NO2, and PO4. In WP10 the seven main parameters are covered by the indicators from 22 to 28. There is also an aggregate indicator, 38, specific pollutant load. In WP4 there are only two indicators C19, pollution, and P5, pollution also, but the first is really measured and the last is a public perception. A particular case is the suspended sediment transport. Beside it be a hydromorphological parameter it is also a quality parameter. So it is important to add the parameter TC8, turbidity (Tu). This is also included in WP5 and in WP10, in last case as indicator 21, transparency. Indeed, the suspended sediment may have different sources, such inorganic grains, inert or with attached substances, pollutant or not, and also organic and biological matter. A final note shall be done to distinguish between the status of water chemical quality and the causes of its status. So important is to know how the water is than from and how much causing factors are entering in water. Consequently, in WP3, WP5 and WP10 there are parameters dealing in a certain way with the sources of pollutants. For instance in WP3 they are identified the urban runoff, mining, industrial, road, agricultural and sewage sources. In WP 10 it is included the indicator 40, “nutrient immision”. It was not needed to specify parameters for the sources of the pollutants in the present analysis of techniques for river rehabilitation. This is in accordance with the adoption for the water amount; they are not parameters for the genesis of river discharge. The last set of ecological parameters is for the biology. They are indicate only 3 parameters in the WFD, and they are adopted in the present analysis, TB1, composition and abundance of aquatic flora (CAaf), TB2, composition and abundance of benthic invertebrate fauna (CAbif), TB3 and composition, abundance and age structure of fish fauna (CAff). In WP3 it is adopted only the first type of data, which results from the present situation of implementation of WFD where only the first parameter has enough studies to be applied in practice by all countries in a harmonized way. In WP4 there is the indicator R9, the biological diversity, but also more 3 indicators for riparian vegetation, R10 to R12. It is also proposed a parameter for this in the techniques. In WP5 it is also referred a parameter for the sediment quality and a few parameters for bank vegetation. The WFD parameters are also adopted in WP with indicators 11 to 13, beside the global biological parameter 6. However they are also included more biological indicators, from 44 to 47, dealing with biomass and densities, and also an indicator for the width of riparian fringe, 41.



In the techniques for urban river rehabilitation it is proposed the parameter TB4, riparian vegetation (RV), because they have also an important structuring function in the river bank, beside the ecological and landscape functions. To complete the physical properties of the rivers necessary to cope with all aspects of river rehabilitation they are added two more parameters for the flood aspects. The proposed parameters are the TS1 (S for social), flooded area (Fa), and TS2, flood risk (HfVf). The flooded area is self explained, it measures the flood prone area, and it defines an important river adjacent area where some constraints to the city development must be taken into consideration. Internationally the 100 years return period is admitted, but in each particular case other period may be adopted with pertinent justification. In WP4 there is the indicator R13, flood vulnerability and in WP5 the flood risk area is referred to. The measure of flood risk is provided by the product of the water depth and water velocity in the flooded area. This product is internationally adopted as a measure of personnel or infrastructure flood risk. Larger numbers are associated a more dangerous and destructive floods. The flood risk is adopted in WP3, in WP4 with indicator P4, perception of flood risk, WP5, and in WP10, indicators S20, flood risk and S24, fear of hazardous floods. Another social parameter is proposed in the river rehabilitation techniques, the TS3, intervention acceptation (IA). This measure the acceptability of the projected designed or concluded rehabilitation. Inquires and public participation are the base to determine it. Finally, the last set of indicators is dedicated to the economic aspects. They are proposed only 3 parameters, two last included in the WP5 and one of them in WP10, EN4, and the first included in WP10, EN6. The parameters are TE1, flood damage cost (FC), TE2, capital cost (CC), and TE3, annualized maintenance cost (MC). In summary, they are proposed a minimum of 29 parameters to deal with techniques for river rehabilitation. They are divided in 23 related with WFD, 3 with social aspects and 3 with economic aspects. The 23 ecological parameters are divided in 11 for hydromorphological aspects, 8 for chemical aspects and 4 for biological aspects. The proposed parameters are in general agreement with the parameters and indicators proposed in WP3, WP4, WP5 and WP10.



5. Development of options 5.1 Introduction In WP5 the second process in the assessment of the potential for rehabilitation is the process 2a, development of options. This process is divided in four parts:

1) site selection; 2) identify options; 3) describe the consequences of options; 4) score options.

The site definition, first than site selection, was presented in chapter 3 of present methodology. The identification of options is mainly an expertise task to be done by a multidisciplinary team covering a large spectrum of skills. Even in the case it will be a small in stream intervention, an enlarged overview of different aspects shall be taken into consideration, namely the imposed constrains by the presence of the city, and the public participation, saw as input of data and decision help. In the description of the consequences the maximum of technical intervention is attached. The modelling of consequences is dominantly a technical aspect. The scoring of options is again a team task, to safeguard all important aspects in the development of options. The following sections of the methodology present the three remaining three parts of the second process applied to the techniques for river rehabilitation. 5.2 Identify options According to WP5 a set of realistic options need to be developed for consideration. This part of the process may be done in three actions:

1. Consider controlling factors 2. Consider objectives 3. Consider likely cost.

To obtain a good set of potential options it must be obtained professional advice in drawing up a list. The level of detail required will depend upon the stage that the project has reached. At feasibility stage then one may only require an outline of each option. At this stage it is important that the options should cover a wide range. At later stages of project



development attention may be concentrated on a smaller range but may need to be described in more detail. The controlling factors were presented in section 4.5. All options shall take into consideration all those factors, the minimum proposed, and expanded as necessary to cover all particular aspects. The objectives for urban river rehabilitation were presented in section 4.3. All options shall be directed to the objectives. In the process the broad objectives are to be focused in specific objective. For each specific objective there in general a set of elements of the global option. That is an option is a set of elements, each attaining a specific objective. Within an urban context there are often constraints that limit the potential for river rehabilitation. The situations that can potentially arise are so diverse that it is not possible to list all the potential constraints that have to be considered. In WP5 they are presented four examples of constraints:

a) the presence of contaminated soil in the banks of the river may preclude any changes to the banks of the river channel as this might release contamination into the river system;

b) the presence of contaminated land near the banks of the river may preclude changes to the flow regime of the river that would permanently raise water levels as increased water levels might lead to mobilisation of contaminants within the groundwater system; and it may also limit the potential for channel re-alignment if the new channel cannot be constructed within the contaminated area;

c) the presence of drainage outlets along the river bank may significantly affect the cost of any channel re-alignment if this would involve modification or relocating the outfalls; and to avoid this cost it may be necessary to constraint any changes to the alignment of the river so that the existing outfalls can be retained;

d) the presence of services, such as gas, electricity or water mains may constrain the potential for changes to the bank profile or for channel realignment if they are buried within or close to the river bank; and the cost of moving such services may be prohibitively expense. There may also be services running under the bed of the river channel. This may constrain options for modifying the bed of the channel.

It is evident by these examples only a large team including all stakeholders can prevent the identification of options that are from the beginning condemned. In Recommendations 8.1, Recommendations 8.2, Specifications 8.1 and Specifications 8.2 are presented the base for technical intervention in river rehabilitation. The first two documents present the background and in the specifications are presented the details for the techniques.



Considering all elements included in the Recommendations 8.1 the following two steps are recommended to identify options for urban river rehabilitation, or to consider the re-naturalisation of the flow regimes in urban rivers:

1) To chose the measures to be designed for the river basin or/and river channels and banks. The measures described in chapter 5 have the effect of recovery to the previous situation.

Documents

Urban River Basin Enhancement Methods - FenixEduruif/FCT/RiverRehab/Rocha_Alves.pdfNew techniques for urban river rehabilitation (WP8) URBEM Deliverable 8-1 • New techniques for