HYDROLOGICAL PROCESSES, VOL. 10, 1021-1025 (1996)

THE LISEM PROJECT: AN INTRODUCTION

A. P. J. DE ROO Department of Physical Geography, Utrecht University, PO Box 80.115. 3508 TC Utrecht, The Netherlands

ABSTRACT In the loess area of The Netherlands a soil erosion project has been carried out to examine the present-day amounts of overland flow, erosion and deposition in drainage basins in the South Limburg region and to assess the effects of conservation measures and land use changes using simulation models. As part of the project, which was ordered by the Province of Limburg, the Waterboard ‘Roer en Overmaas’, the Ministry of Agriculture and 14 municipalities of South Limburg, the physically based hydrological and soil erosion model LISEM (the Limburg soil erosion model) has been developed. In this paper the history and scope of the project are explained, as well as the field and laboratory programme. In addition the research drainage basins are described.

KEY WORDS: soil erosion; hillslope hydrology; catchment hydrology; simulation models

SOIL EROSION PROBLEMS IN SOUTH LIMBURG

Soil erosion and surface runoff have always been problems concomitant with intensive agricultural land use in hilly areas. These problems can be exacerbated by soii and geology, as is the case in the hill country of South Limburg (The Netherlands), where soils developed bi: loess are especially vulnerable to surface runoff and soil erosion. Since people started clearing the forests, soil erosion processes and human reactions to them have created the characteristic landforms of dry valleys, incised (hollow) roads and lynchets.

Until recently, traditional land use practices could keep soil erosion and surface runoff at acceptable levels. During the last two decades, however, the expansion of urban areas, the increased area of sealed surfaces and the intensification of agriculture, and increased arable agriculture, have caused soil erosion and flooding to increase. Re-allotment schemes have resulted in larger fields, causing surface runoff to be more erosive. Changes in land use also contribute to increasing erosion, total runoff and peak runoff. The area of grassland has decreased in favour of urban areas and, after 1975, in favour of arable land (De Roo, 1993). Moreover, there has been a change in land use and in the kinds of crops grown in South Limburg. Between 1960 and 1986, crops which give rise to a higher erosion risk, such as maize and sugar-beet, have increased in South Limburg, replacing cereals such as winter wheat. Runoff with a high sediment load causes obstructed waterways and choked up sewers, causing damage to roads, gardens and houses.

In the small hilly area (20 x 25 kilometres) of South Limburg we find a dense population, together with an intensively used agricultural area on severely erosive loess soils. Large parts of this region were subject to re-allotment schemes, resulting in larger fields, while characteristic landforms such as lynchets and incised roads were removed, thus increasing the erosive power of overland flow.

SCOPE OF THE PROJECT

Since 1980, awareness of soil erosion problems in South Limburg has increased. Schouten et al. (1985) were among the first to report the causes and damaging effects of surface runoff and soil erosion. However,

CCC 0885-6087/96/08/ 1021/05 0 1996 by John Wiley & Sons, Ltd.

Received 10 April 1995 Accepted 24 August 1995

1022 A. P. J. DE ROO

quantitative information on soil erosion rates and the effects of conservation strategies was not available. Local and provincial policy makers and other parties concerned (both farmers organizations and environmental groups) needed a quantitative evaluation of the extent and the magnitude of the soil erosion problems and the possible management strategies in South Limburg on a regional basis. Therefore, field measurements were necessary. Also, there was a need for quantitative simulation models of surface runoff and soil erosion, which can be used to evaluate alternative strategies for improved land management, not only in the monitored areas, but also in ungauged catchments.

Between 1991 and 1994, a soil erosion project has been carried out in three catchments in the loess area of South Limburg, The Netherlands. The project was funded by the Province of Limburg, the Waterboard ‘Roer en Overmaas’, the Ministry of Agriculture and 14 municipalities of South Limburg. The Departments of Physical Geography at the Universities of Utrecht and Amsterdam, and the Soil Physics Division of the Winand Staring Centre in Wageningen cooperated in this project.

The government institutions were interested because: (i) at that time there was no central government soil erosion policy; (ii) a large part of South Limburg is susceptible to soil erosion; and (iii) erosion and its related effects cause damage: flooding and damage to private properties and infrastructure, loss of fertile topsoil, washing away of seedlings, reduced crop yields, and loss of fertilizers, herbicides and pesticides, locally entering nature areas. Therefore, the government proposed to develop a framework within which local and provincial plans for the rural area could be tested with respect to their effects on soil erosion and flooding. Also, there was a demand for research of accurate soil conservation measures and their most suitable locations, thus leading to a reduction of the problem to an acceptable level. Within this scope, as a tool for planning and conservation purposes, a new physically based hydrological and soil erosion model needed to be developed and tested: the umburg Soil Erosion Model (LISEM).

LOCATION OF THE RESEARCH SITES

To obtain a representative idea of the extent of the soil erosion problem for the region and the validity of the LISEM model, the research was concentrated on three catchments in South Limburg (Figure 1). The

Figure 1. Location of the research catchments in the South Limburg loess area

THE LISEM PROJECT 1: INTRODUCTION

Table LCharacteristics of the research catchments

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Catsop St Gillisstraat Etzenrade

Area (km2)

Slope gradient (%) 0-2 2-5 5-10 10-15 15-18 >18

Soil type Luvisols (ABC) Eroded luvisols (BC) Eroded luvisols (C) Colluvial soils Soils on limestone Gravelly and sandy soils Land use Roads and built up areas Grassland Arable

winter wheat sugar-beet potatoes maize orchard other

0.42

4.1 34.7 47.1 10.5 2.1 1.4

8.4 40.0 24.5 27.1 0 0

0.8 13.2 86.0 32.6 30.8 16.81 1.6 0 4.2

0.43

11.8 27.6 44.5 15.6 0.6 0.0

25.0 30.0 20.0 10.0 15.0 0

0.4 5.5

94.1 11.7 19.2 3.4

21.2 27.5

1.1

2.24

38.0 34.8 19.7 5.6 1.1 0.8

36.3 26.1 7.7

29.4 0 0.5

3.1 14.1 82.8 18.3 24.3 10.0 23.2

1.1 5.9

South Limburg region, as well as the three research catchments, has a gently to moderately sloping topography. The soils are developed mainly in loess deposits: luvisols, eroded luvisols and colluvial soils. The land use in the research catchments is predominantly arable, with winter wheat, sugar-beet, potatoes and maize as the main crops (Table 1).

THE FIELD AND LABORATORY PROGRAMME

The research in the LISEM project consists of three parts: a field study, a laboratory study and a model simulation study. The field investigations have been carried out at three scales: the hillslope scale, the (small) subcatchment scale and the catchment scale (Figure 2). The three scales have been chosen to investigate the hillslope hydrology and sediment and runoff source areas in detail.

The catchment level is needed to be able to predict downstream effects of water and sediment entering the villages. In the three catchments, discharge and sediment load at the basin outlet have been measured continuously over two and a half years, to allow validation of the LISEM model. Rainfall has been measured at six locations to take into account the spatial variability of rainfall. The soils in the catchments were mapped in detail to serve, amongst other purposes, as a basis for the soil hydrological submodel (Leenders, 1993). Several times during the year, land use and soil cover, surface roughness parameters (Cremers et al., 1996) and soil shear strength were measured. At the same time soil samples were taken. Finally, in the laboratory, soil physical and soil chemical properties, such as soil texture, organic matter content, aggregate stability, water retention and hydraulic conductivity curves (Stolte et al., 1996) were measured to support the LISEM model with input data. Furthermore, at the second scale, in six subcatchments, discharge and sediment load measurements were carried out, to allow validation of the model and locate source areas (Van Dijk and Kwaad, 1996). In addition, at the

1024 A. P. J. DE ROO

-250 m

Figure 2. Experimental setup in the Ransdaal (St.Gillisstraat) drainage basin (South Limburg, The Netherlands)

third scale, at twelve sites in the catchments along four slope profiles, continuous soil suction measurements were performed to assess both vertical and lateral transport of water in the soil (Ritsema et al., 1996a).

Throughout the Limburg region experiments have been carried out on small field plots and on slopes to investigate the effects of alternative tillage systems (e.g. direct drilling, mulching) (Van Dijk et al., 1996a) and nature conservation measures (buffer strips, grassed waterways) under artificial rain using rainfall simulators and natural rain (Van Dijk et al., 1996b). These measurements could also be used to validate the simulations of conservation practices.

THE MODELLING PROGRAMME

The last part of the project consists of the development of a simulation model and simulations of the effects of several scenarios on catchment hydrology and soil erosion. Based on experiences with the ANSWERS erosion model (Beasley et al., 1980; De Roo et al., 1989; De Roo, 1993) and the hydrological SWATRE model (Belmans et al., 1983), the new physically based hydrological and soil erosion model LISEM has been developed and tested (De Roo et al., 1996a). During the development of LISEM vertical and lateral flow has been evaluated using a submodel (Ritsema et al., 1996b). LISEM simulates a catchment during and immediately after a rainfall event. The model has been tested using available data from the hillslope, the subcatchment and the catchment scale measurements (De Roo et al., 1996b).

Finally, several scenarios that might reduce the magnitude of the erosion and flooding problems have been put together and simulated using the model. The scenarios consist of combinations of the following possible conservation measures: engineering ponds or storage basins; tillage: mulching, direct drilling, fertilizing crops, cover crops; nature conservation: grassed waterways and ‘buffer strips.

ACKNOWLEDGEMENTS

This project has been largely funded by the following organizations: the Province of Limburg, the Waterboard ‘Roer en Overmaas’, the Ministry of Agriculture and 14 municipalities of South Limburg: Eijsden, Gulpen, Maastricht, Margraten, Meerssen, Nuth, Onderbanken, Schinnen, Simpelveld, Stein, Vaals, Valkenburg, Voerendaal and Wittem.

Several researchers have contributed to the project. Mr C. G. Wesseling, Mr N. H. D. T Cremers, Mr M. A. Verzandvoort, Mr R. J. E. Offermans and Mr H. Kolenbrander of Utrecht University, Mr C. J. Ritsema,

THE LISEM PROJECT 1: INTRODUCTION 1025

Engineers J. Stolte and K. Oostindie of the Winand Staring Centre Wageningen and Mr F. J. P. M. Kwaad, Mr P. M. Van Dijk, Dr A. C. Imeson and Mr M. Van Der Zijp of the University of Amsterdam are all thanked for their contributions.

Furthermore, the stimulating comments of the Provincial Erosion Working Group (Dr J. Duijsings, Dr Ir. T. Segeren, Engineer Th. Kraak, Ir. D. Koeman, Ir. H. Caubo, Engineer P. Geelen, Mr W. Lemmerlijn and Mr R. Cleef) during the project are greatly appreciated.

REFERENCES

Beasley, D. B., Huggins, L. F., and Monke, E. J. 1980. ‘ANSWERS a model for watershed planning’, Trans. M A E , 23, 938-944. Belmans, C., Wesseling, J. G. and Feddes, R. A. 1983. ‘Simulation model of the water balance of a cropped soil SWATRE, J , Hydrol.,

Cremers, N. H. D. T., Van Dijk, P. M., De Roo, A. P. J., and Verzandvoort, M. A. 1996. ‘Spatial and temporal variability of soil surface roughness and the application in hydrological and soil erosion modelling’, Hydrological Processes, 10, 1035-1047.

De Roo, A. P. J. 1993. ‘Modelling surface runoff and soil erosion in catchments using Geographical Information Systems; validity and applicability of the ANSWERS model in two catchments in the loess area of South Limburg (The Netherlands) and one in Devon (UK)’, Netherlands Geog. Stud., 157, 295 pp.

De Roo, A. P. J., Hazelhoff, L., and Burrough, P. A. 1989. ‘Soil erosion modelling using ANSWERS and Geographical Information Systems’, Earth Surf. Proc. Landf., 14, 517-532.

De Roo, A. P. J., Wesseling, C. G., and Ritsema, C. J. 1996a. ‘LISEM: a single-event physically based hydrological and soil erosion model for drainage basins. I: theory, input and output’. Hydrological Processes, 10, 1107-1 117.

De Roo, A. P. J., Offermans, R. J. E., and Cremers, N. H. D. T. 1996b. ‘LISEM: a single-event, physically based hydrological and soil erosion model for drainage basins. 11: sensitivity analysis, validation and application’, Hydrological Processes, 10, 1 119-1 126.

benders, W. H. 1993. ‘Soils of the three catchments of the erosion project South-Limburg’, The Winand Staring Centre, Report no. 270, Wageningen, The Netherlands. 72 pp [in Dutch].

Ritsema, C. J., Stolte, J., Oostindie, K., Van Den Elsen, E. and Van Dyk, P. M. 1996a. ‘Measuring and modelling of soil water dynamics and runoff generation in an agricultural loessial hillslope’, Hydrological Processes, 10, I08 1-1089.

Ritsema, C. J., Oostindie, K., and Stolte, J., 1996b. ‘Evaluation of vertical and lateral flow through agricultural loessial hillslopes using a two-dimensional computer simulation model’, Hydrological Processes, 10, 1091 -1 105.

Schouten, C. J., Rang, M. C., and Huigen, P. M. J. 1985. ‘Erosie en wateroverlast in hid-Limburg (Soil erosion and flooding in South Limburg)’, tnmdschap, 2, 118-132.

Stolte, J., Ritsema, C. J., Veerman, G. J., and Hamminga, W. 1996. ‘Establishing temporally and spatially variable soil hydraulic data for use in a runoff simulation in a loess region of The Netherlands’, Hydrological Processes, 10, 1027-1034.

Van Dijk, P. M., and Kwaad, F. J. P. M. 1996. ‘Runoff generation and soil erosion in small agricultural catchments with loess-derived soils’, Hydrological Processes, 10, 1049-1059.

Van Dijk, P. M., Van Der Zijp, M., and Kwaad, F. J. P. M. 1996a. ‘Soil erodibility parameters under various cropping systems of maize’, Hydrological Processes, 10, 1061 - 1067.

Van Dijk, P. M., Kwaad, F. J. P. M., and Klapwijk, M. 1996b. ‘Retention of water and sediment by grass strips’, Hydrological Processes, 10, 1069-1080.

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