Metodika en final

Програма за ТГС по ИПП България – Сърбия

EUROPEAN UNION Bulgaria – Serbia IPA Cross-border Programme

“Assessment of flood risk – a base for sustainable development in upper part of Nishava

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DEVELOPMENT OF A UNIFORM TRANS-BOUDARY METHODOLOGY FOR

FLOOD RISK ASSESSMENT

CONTENTS:

INTRODUCTION

CHAPTER ONE

1. USED TERMINOLOGY

2. EUROPEAN APPROACHES

3. LEGISLATION AND INSTITUTIONAL FRAMEWORK

4. DATABASE

5. TYPES OF FLOODS

CHAPTER TWO

1. COMMON APPROACH

2. HYDROLOGY

2.1. DETERMINATION OF THE MAXIMUM RUN-OFF

2.2. CLIMATE CHANGE

3. GEODESY

3.1. COORDINATE SYSTEMS AND PROJECTIONS

3.2. DIGITAL TERRAIN MODEL

3.3. ADDITIONAL ANALYSIS OF THE DIGITAL TERRAIN MODEL

3.4. GEODESIC SHOOTING

4. HYDRAULIC MODELLING

4.1. CALCULATION METHODS AND PROGRAMMES

4.2. CREATION OF A HYDRAULIC MODEL

CHAPTER THREE

1. FLOOD HAZARD MAPS

1.1. DETERMINATION OF THE INUNDATED AREAS

1.2. КCORRECTION OF THE INUNDATED AREAS

1.3. PROTECTION MEASURES

1.4. FORMATTING OF THE MAPS

2. FLOOD RISK MAPS

1.5. RISK MAPPING APPROACHES




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1.6. SOCIO-ECONOMIC ASPECTS

1.7. RISK CLASSIFICATION

1.8. FORMATTING OF THE MAPS

CHAPTER ONE

EUROPEAN APPROACH

Czech Republic

Orthophotos and topographic maps, scale of 1:10 000, are used as a basis for the

preparation of flood hazard and flood risk maps in Czech Republic. The orthophotos

and topographic maps are provided by the Czech Surveying Office for Mapping and

Cadastre (file ZABAGED).

Figure 1: Orthophoto and topographic map




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Figure 2: Scheme for flood hazard and flood risk maps elaboration for given scenario

(water quantity).

LEGISLATION AND INSTITUTIONAL FRAMEWORK

General obligations of the parties with respect to the management of flood risk and

cross-border cooperation are determined by international legal frameworks such as

the Water Convention of the UNECE and the Floods Directive of the EU.

National legislation should set clearly defined and allocated responsibilities and rights

of all institutions and organizations that are relevant to flood risk management.




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Figure 3. Legislation and institutional framework in flood risk managament




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Figure 4 Current organization of water management in Republic of Serbia




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Figure 5 Scheme Structure of the specialized institutions in flood risk management

DATABASE

Categories of databases:

Basic data

Hydrology

Hydraulics

Climate

Damage assessment

TYPES OF FLOODS

The main feature for typifying floods is their source. Depending on it, the following

types of floods can be defined: "sea floods", "river flooding", "rain floods", "

groundwater floodings" and "infrastructure floodings".

CHAPTER TWO




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5. HYDROLOGY

5.1. DETERMINATION OF THE MAXIMUM RUN-OFF

Statistical methods

The statistical methods are applicable for determination of the maximum run-off in

basins with built hydrometric network and an area greater than 1000 km. The

statistical methods are applied in both countries.

Models „rainfall – run-off”

Figure 6 Model „Rainfall – run-off”

Method for regionalization of the maximum run-off

Eight factors and characteristics of drainage basins and river systems that are

essential for the formation of maximum flow are set out in LUBW, 2007:

• area of the catchment AEo [km2]

• urbanized territory S [%]

• afforestation W [%]




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• average slope Ig [%]

• river length L [km] along the main rivers of the watershed to the confluence

• river length LC [km] from the center of gravity of the catchment to its estuary;

• average annual rainfall in the catchment hNG [mm]

• landscape factor LF [-]

GEODESY

DIGITAL TERRAIN MODEL

A variety of sources can be used to create a terrain elevation model: topographic

maps, satellite images, orthophotos, surveys of the river flow, LIDAR. The described

sources are characterized by different accuracy of the topographical information.

Therefore, the combined use of these sources is recommended to obtain a digital

terrain model with sufficient accuracy.

Figure 7 Geodesic measurements /shooting of cross-sections/




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Figure 8 Encoding of the cross section folds based on inverted cross sections of the

plane

Figure 9 Generation of 3D folds of the river bed terrain




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Figure 10 Digital terrain model, developed on the basis of laser scanning data

Figure 11 Digital terrain model of river section, developed with laser scanning data





Figure 12 conbination of laser scanning data, geometry of the facilities and folds f the

terrain structure

GEODESIC SHOOTINGS





Figure 13 Method of the profiles

1. HYDRAULIC MODELLING

1.1. CALCULATION METHODS AND PROGRAMMES

Use of 1D model for river section calculation (i.e. HEC-RAS)

In these models, the geometry of the river valley and the river bed is laid depending

on multiple cross sections. The hydraulic impact on equipment and hinders in the

riverbed,on the local expansion or narrowing, of the changes in the slope of the river

bed, etc. can be reproduced by 1D-models of the river flow.





Figure 14 Determination of cross-sections for hydraulic measurements of the digital

terrain model (based on topographic maprs 1:5000)

Figure 15 Calculated inundated areas from 1D calculations

1.2. CREATION OF A HYDRAULIC MODEL

Use of 2D models of the river sections (i.e. Hydro_AS-2D)





Figure 16 2D-calculation network of the basis of elevation sports connection of

SRTM-elevation terrain model, (basis: Google Earth)

Figure 17 Calculated inundated area with 2D hydraulic measurements (basis: Google

Earth)

Use of hydrologic model, based on calculation raster network for 2D calculations of

the surface run-off (i.e. GSSHA model)





Figure 18 Image of the modelled area with run-off model (GSSHA) based on

calculation raster network.

CHAPTER THREE

FLOOD HAZARD MAPS

Flood hazard maps are made for the following scenarios:

flooding with low security or high repetition period (extreme floods);

flooding with medium security (≤ 1%), respectively, with an average repetition periods (≥ 100 years);

individually, floods with high security or a small repetition period.

In compliance with the flood risk directive, flood hazard maps must contain the following information:

of flooding;

of flooding and water levels;

individually, flow velocity or the relevant water flow.





Figure 19 Borders of inundation and calcualted depths of floods during high wave

with repetition period 100 years, respectively 1% security.

незастрашени сгради

потенциално застрашени сгради

легенда:заливни дълбочини за висока вълна с

период на повторение 100 години [см]

степен на застрашеност на сгради:

залети площи

площи със свободен борд < 30 см

незастрашени сгради

потенциално застрашени сгради

легенда:заливни дълбочини за висока вълна с

период на повторение 100 години [см]

степен на застрашеност на сгради:

залети площи

площи със свободен борд < 30 см

легенда:

застрашени зони при висока вълна с

период на повторение (ПП):

10 години

20 години

50 години

100 години

oпасност от заливане на сгради:

незастрашени

слабо застрашени (ПП > 100 год.)

средно застрашени (ПП 20 -100 год.)

силно застрашени (ПП < 100 год.)

легенда:



10 години

20 години

50 години

100 години






легенда:



10 години

20 години

50 години

100 години










Figure 20 Borders of inundation for floods with repetition period 10, 20, 50 и 100

years, respectively 10%, 5%, 2% и 1% security.

Figure 21 Determination of the flood hazard in Wallone





Figure 22 Integration of the determination methods of the repatition and inundation of

the river

Figure 23 Exemplary flood hazard map





Figure 24 Exemplary flood risk map

PROTECTION MEASURES

If there are protective measures against flooding, it does not necessarily mean that

the location is protected from flooding. Often there are protection measures which do

not functioning normally due to lack of maintenace and no longer correspond to the

modern technologies. Even with perfectly working facilities it must be alwasys

considered that they can not provide absolute protection at a certain risk. Often the

protection degree of the protection measures is not known exactly, so it is difficult to

accurately estimate the effect of the measures, in example for HQ100

FORMATTING OF THE MAPS

According to the Floods Directive, the flood risk assessment should covere the

negative impacts on the following protected categories "human health",

"environment", "cultural heritage" and "business". A prerequisite for achieving this

goal is the definition of clear criteria for assessing the negative effects on each

protected category separately.

CALSSIFICATION OF THE RISK





Figure 25 Exemplary map of classification of the inundated areas

Technology

Metodika en final