European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

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B4-3040/97/730/JNB/C4

by S. Dautrebande, J.G.B. Leenaars, J.S. Smitz & E. Vanthournout (eds.) May 2000

European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

7$%/(2)&217(176 5SCENARIO DEVELOPMENT ...... 59

5.1 INTRODUCTION...... 59

5.2 APPROACH ...... 59

5.3 IDENTIFICATION OF ALL POTENTIAL MEASURES ...... 60

5.4 GROUPING OF MEASURES ...... 60

5.5 RANKING OF MEASURES PER ‘MODEL-BASED’ GROUP ...... 61

5.6 SELECTION OF SCENARIOS TO BE USED IN THE STUDY ...... 62

 +<'52/2*,&$/678'<   6.1 INTRODUCTION...... 65

6.2 OBJECTIVES...... 65

6.3 METHODOLOGY AND APPROACH ...... 65

6.4 INPUT DATA FOR THE HYDROLOGICAL STUDY ...... 66

 /LPQLPHWULFGDWD   &OLPDWLFGDWD    *HRJUDSKLFGDWD   6.5 HYDROLOGICAL CHARACTERISATION OF THE GEUL RIVER CATCHMENT AREA...... 69

 )ORRGIUHTXHQF\DQDO\VLV    &KDUDFWHULVWLFHYHQWV    :DWHUEDODQFHRIWKHFDWFKPHQWDUHD   6.6 MODEL DEVELOPMENT...... 72

 'HVFULSWLRQRIWKHPRGHO  6.6.1.1 Soil sub-model EPIC-GRID...... 73 6.6.1.2 The groundwater sub-model ...... 73 6.6.1.3 The master code ...... 73

 6FKHPDWLVDWLRQRIWKHFDWFKPHQW  6.6.2.1 Preparation of the spatial data...... 74 6.6.2.2 Determination of initial parameters...... 76

6.7 MODEL VALIDATION ...... 76

 6HOHFWLRQRIWKHVLPXODWLRQSHULRG   5HVXOWVRIWKHYDOLGDWLRQ   &RQFOXVLRQVRIWKHYDOLGDWLRQ   6.8 MODEL APPLICATION AND SCENARIO SIMULATION ...... 80

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Table of contents I European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

 5HVXOWV  6.9 CONCLUSIONS ...... 85

6.10 RECOMMENDATIONS ...... 86

6.11 ACKNOWLEDGEMENT...... 86

 +<'52'<1$0,&678'<   7.1 INTRODUCTION...... 87

7.2 OBJECTIVES...... 88

7.3 APPROACH ...... 88

7.4 MODELLING OF THE GEUL AND ITS TRIBUTARIES ...... 89

 7KH,6,6PRGHOOLQJSDFNDJH    0RGHOVHWXS   7.4.2.1 Topological discretisation...... 90 7.4.2.2 Hydraulic structures...... 90 7.4.2.3 External boundary conditions ...... 93

 &DOLEUDWLRQDQGYHULILFDWLRQRIWKHPRGHO  7.5 SIMULATIONS ...... 94

 'HVFULSWLRQ    5HVXOWV  7.6 CONCLUSIONS AND RECOMMENDATIONS ...... 101

 /(*$/)5$0(:25.  8.1 INTRODUCTION...... 105

8.2 THE NETHERLANDS...... 106

 $FWRUVLQWKH'XWFKLQVWLWXWLRQDOOHJDOIUDPHZRUN   ,QVWUXPHQWV    7KHDSSOLFDELOLW\PDWUL[  8.2.3.1 National level...... 109 8.2.3.2 Provincial level ...... 110 8.2.3.3 Local level...... 111

 &RQFOXVLRQVRQWKH'XWFKOHJDOIUDPHZRUN   5HFRPPHQGDWLRQV  8.3 BELGIUM ...... 113

8.4 THE FLEMISH REGION ...... 114

 $FWRUVLQWKH)OHPLVKLQVWLWXWLRQDOOHJDOIUDPHZRUN  8.4.1.1 Regional level ...... 114 8.4.1.2 Provincial level ...... 115

Table of contents II European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

8.4.1.3 Local level...... 115

 ,QVWUXPHQWV   8.4.2.1 Water-resources management ...... 116 8.4.2.2 Land use planning...... 119 8.4.2.3 Land use and agricultural policy...... 121 8.4.2.4 Environmental policy...... 122

 7KHDSSOLFDELOLW\PDWUL[   &RQFOXVLRQVRQWKH)OHPLVKOHJDOIUDPHZRUN   5HFRPPHQGDWLRQV±)OHPLVK5HJLRQ  8.5 THE WALLOON REGION...... 132

 $FWRUVLQWKH:DOORRQLQVWLWXWLRQDOOHJDOIUDPHZRUN   8.5.1.1 Regional level ...... 132 8.5.1.2 Provincial level ...... 132 8.5.1.3 Local level...... 133

 ,QVWUXPHQWV   8.5.2.1 Water-resources management ...... 134 8.5.2.2 Land use planning...... 137 8.5.2.3 Agricultural policy...... 139 8.5.2.4 Environmental Policy...... 140

 7KHDSSOLFDELOLW\PDWUL[   &RQFOXVLRQVRQWKH:DOORRQOHJDOIUDPHZRUN    5HFRPPHQGDWLRQVIRUWKH:DOORRQUHJLRQ  8.6 CONCLUSIONS AND RECOMMENDATIONS ...... 150

 &21&/86,216   9.1 CONCLUSIONS ON THE TERRITORIAL DATA INVENTORY ...... 154

9.2 CONCLUSIONS ON THE PRELIMINARY RISK ANALYSIS...... 155

9.3 CONCLUSIONS ON THE PRELIMINARY HYDROLOGICAL ANALYSIS (CF. ANNEXE D) ...... 155

9.4 CONCLUSIONS ON THE SCENARIO DEVELOPMENT...... 156

9.5 CONCLUSIONS ON THE HYDROLOGICAL STUDY ...... 156

9.6 CONCLUSIONS ON THE HYDRODYNAMIC STUDY ...... 157

9.7 CONCLUSIONS ON THE LEGAL FRAMEWORK ...... 158

9.8 FINAL CONCLUSIONS ...... 159

 5(&200(1'$7,216  

 5()(5(1&(6  

Table of contents III European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

 6&(1$5,2'(9(/230(17

 ,QWURGXFWLRQ This project is aimed at the identification of environment-friendly measures to decrease the risk of flash floods in the catchment of the Geul river. Based on the assumption that the change in land use during the last 30-50 years is one of the factors that may increase the flash flood problems, two basic scenarios, representing the land use in the 1950’s and the present land use, have been selected. These two scenarios can be considered as being representative of the changes in land use and the related increase of fast runoff. It was obvious to all stakeholders that the current land use situation cannot be reverted to the old 1950’s state. Therefore other measures to obtain flash flood reducing results have been identified as well. In the present chapter the procedure for selecting these measures and identifying the scenarios (or set of measures), which will be used in the simulations, is described. The scenarios include both ‘hydrological’ measures (actions in the catchment) and ‘hydraulic’ measures (actions in the riverbed).

 $SSURDFK To develop the scenarios, a step-by-step procedure was followed: 1. Identification of all potential measures 2. Definition of coherent groups of measures 3. Ranking of measures (per group) 4. Preparation of possible scenarios (by technical team) 5. Ranking of possible scenarios 6. Selection of scenarios to be simulated in the project

The project stakeholders were requested to participate in each process-step, for this is a prerequisite for obtaining realistic and feasible scenarios and for ensuring a strong involvement of the regional authorities. Due to some determinant aspects in this Geul project regarding (1) the attempt to simulate spatially distributed aspects, for instance land use changes and agricultural practices, in a deterministic way, (2) the lack of knowledge concerning the hydrological process related to different land use types, (3) the requirement that the impact of implemented measures could be studied, and (4) the limited financial resources, several decisions had to be made: 1. Only three extra scenarios, at the utmost, were to be identified; 2. The scenarios should not consist of more than one measure with spatial characteristics (hydrological model) and one hydraulic infrastructure measure

Scenario development 59 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

(hydrodynamic model) in order to facilitate the analysis of the relation between impact and specific measure; 3. A measure should be identified within the technical limits of the simulation models, the scale used for the model-input and the knowledge available in literature.

 ,GHQWLILFDWLRQRIDOOSRWHQWLDOPHDVXUHV Based on a review of the present literature and a brainstorming with the project-team a preliminary list of measures was formulated. The list consisted of forty-two different measures, which could be divided in three major groups. These main groups of measures are presented in Table 5.1; the full list is shown in Annexe F.1.

Table 5.1 Main groups of potential measures 0DLQJURXSV *URXSV 1. Awareness-raising measures 1.A. Based on sensitisation 1.B. Based on incentives 2. Technical measures 2.A. Related to environmental planning1 2.B. Related to infrastructure 3. Institutional measures

Of these measures, only the technical measures were relevant to be simulated in this pilot study and selected for the remaining scenario-development procedure steps. Awareness-raising measures and institutional measures have been dealt with during the analysis of the legal framework.

 *URXSLQJRIPHDVXUHV The technical measures (main group 2) were subdivided into two subgroups, namely a group related to environmental planning (2.A) and one related to infrastructure measures (2.B). After a first selection three subgroups were maintained in group 2.A, and five subgroups in group 2.B. These subgroups are presented in table 5.2.

1 Environmental or land use planning

Scenario development 60 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Table 5.2 Types of measures to be used in the scenario development, maintained after a first selection process *URXSV 6XEJURXSV 2.A. Related to environmental planning 2.A.1 Adjustment of the riverbed 2.A.2 Adapted land use 2.A.5 Adjustment of parcel borders - land plots

2.B. Related to infrastructure measures 2.B.2 Adjustment of the riverbed 2.A.1.b Restoration of meandering 2.B.3-4 Storage basins 2.A.2.e Buffer-zones along the river and grassed waterways 2.B.8 Bridges and structures restricting the water-flow

 5DQNLQJRIPHDVXUHVSHUµPRGHOEDVHG¶JURXS In each subgroup several measures were defined. This resulted in six measures for type 2.A.1, seven measures for type 2.A.2 and one measure for each of the other types (see Annexe F.1). Consequently, a list of approximately twenty potential measures was obtained for the next step in the scenario-development procedure.

Up to here the scenario-development was based on the available knowledge and opinions of the participating stakeholders. The next step had to link the defined measures with the technical features of the simulation-programmes. Therefore a rearrangement of all twenty measures was needed, based on the hydrological and hydrodynamic model characteristics. Four so-called ‘model-based’ groups were distinguished: two groups of measures that could be implemented in a hydrological programme and two groups that could be implemented in a hydrodynamic model. These ‘model-based’ groups are defined as: 1. +\GURORJ\ ,: Spatial measures related to a certain land use type, for which the measures involve the land use practices (mainly agricultural practices); 2. +\GURORJ\,,: Spatial measures resulting in a land use class conversion; 3. +\GURG\QDPLFV,: Measures related to adjustments of the riverbed cross-section; 4. +\GURG\QDPLFV,,: Measures related to the hydraulic infrastructure.

All of the twenty measures could be introduced in one or another part of the simulation model; some could be put in more than one of the model-based groups. Resulting were

Scenario development 61 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas groups with four to six measures. As the condition was made before that a scenario could only consist of one hydrological and one hydrodynamic measure at the most (for simulation facilitating), a ranking of measures was required. This ranking was done by means of a scoring — or priority — procedure. In each group, every stakeholder had to select the two, according to him, most promising and appropriate measures. Based on this selection the measures were ranked, resulting in the following list of ‘most preferred measures’ (Table 5.3, 1 = first choice, 2 = second choice).

Table 5.3 List of most preferred measures

0($685(6 +\GURORJ\ +\GURORJ\ +\GURG\QDPLFV +\GURG\QDPLFV , ,, , ,, 2.A.1.c 1 1 2.A.1.d 2 2.A.2.b 1 2.A.2.e 1 2.B.2 2 2.B.3 2 2 2.B.4 1

The explanation of these measures, while also referring to the codes used in Table 5.2, is given below: - $F (re)allocation/enlargement/extension of floodplains - $G creation of wetlands - $E turn high sloping areas to grassland or wood - $H re-introduction of hedgerows and green belts - % adjustment of the riverbed (modification of cross-section geometry and hydraulic slope) - % storage basins upstream - % retention basins in the riverbed

 6HOHFWLRQRIVFHQDULRVWREHXVHGLQWKHVWXG\ Based on the results of the ranking and the technical features of the models, the technical team of the Geul project defined several scenarios. These scenarios were presented and discussed during the project-team meeting of June 1999. It finally resulted in the selection of three future scenarios, which are combined with the reference

Scenario development 62 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

‘baseline-scenarios’ as defined for the historic land use in the 1950’s and the present land use in the 1990’s.

Table 5.4 Scenarios to be simulated in the hydrological and hydrodynamic studies

6FHQDULR (QYLURQPHQWDOPHDVXUH ,QIUDVWUXFWXUHPHDVXUH 1. 1990-reference current land use actual situation 2. grass on slopes of >12% increased roughness of the river floodplains 3. forest on slopes of >10% actual situation 4. greenbelts / hedgerows addition of 2 constriction devices in the riverbed 5.1950-reference land use of the 50s actual situation

These five scenarios were simulated as part of the hydrological and hydraulic modelling studies, described in Chapters 6 and 7 of this report.

Scenario development 63 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Scenario development 64 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

 +<'52/2*,&$/678'<

 ,QWURGXFWLRQ This hydrological study aims at defining the characteristics of flash flood events in the Geul river catchment and, in particular, at assessing the effectiveness of land use related measures to reduce the risk of flooding. In Annexe F.1, all possible measures are listed. In Chapter 5, some measures are combined into scenarios. The hydrological model will simulate these scenarios. The simulated water-inflow has three components, namely surface runoff, hypodermic flow and groundwater flow. They are simulated by means of an integrated hydrological model. Whether rainfall infiltrates in the upper layers of the soil or runs off superficially is a function of topsoil characteristics, of the soil vertical humidity profile and also of land use characteristics (land use, crop growth, agricultural practices). Consequently, soil characteristics as well as land use changes will affect the infiltration of water into the soil and the superficial runoff. The hydrological study calculates the amount and speed of water flowing from the Geul catchment into the Geul River and its tributaries. The results of the hydrological study are used as input for the hydraulic study (Chapter 7).

 2EMHFWLYHV The objective of the hydrological study is to simulate the hydrological behaviour of the Geul river catchment and to determine the water-flow to the Geul river and its tributaries. This objective is achieved by using a hydrological model of the basin. The hydrological model generates water-fluxes as input for the hydrodynamic model of the river network used in Chapter 7, separately for each environmental scenario defined in Chapter 5.

 0HWKRGRORJ\DQGDSSURDFK The hydrological programme used in this study is part of an integrated hydrological basin-river model, named MOHICAN (02dèle +ydrologique ,ntégré pour le calcul des &rues et l'$mplitude des 1iveaux d'eau). It has been developed for the Walloon Ministry of Equipment and Transport in a multidisciplinary approach. The participating researchers were member of: • three scientific departments of the University of Liège: the "Centre d'Etude et de Modélisation de l'Environnement" (CEME-ULG), the "Laboratoire de Géologie de l'Ingénieur et d'Hydrogéologie" (LGIH-ULG) and the "Laboratoire d'Hydrodynamique Appliquée" (HYD-ULG) (the latter not being involved in the present study);

Hydrological study 65 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

• one scientific department of the Agricultural Faculty of Gembloux (Unit "+\GUDXOLTXH$JULFROH", HA-FSAGx). The soil compartment is represented by the sub-model EPIC-GRID, describing the soil- water dynamics, particularly in relation to crop growth. The Unit "+\GUDXOLTXH$JULFROH" (FSAGx) developed this sub-model. The model includes soil and groundwater processes and transfers from soils and groundwater to the river network. It uses, as much as possible, deterministic and physically-based representations and is oriented towards planning, i.e. the simulation of the effect of environmental management operations or measures in the uplands of the catchment area. The input data, which are necessary to run the programme, include:

1. Information about the SK\VLFDOFKDUDFWHULVWLFV of the catchment area: - physiography of the catchment area (digital elevation model, river network) - soil characteristics - geological characteristics - climatic characteristics 2. Information about the ODQGXVH in the catchment area: - land cover types - land use management, agricultural practices

The soil sub-model calculates direct fluxes to the river network and water-fluxes to the groundwater (effective infiltration). The groundwater sub-system is represented by means of transfer functions. The hydrological programme MOHICAN calculates the distribution of water-fluxes from the soil (runoff, hypodermic fluxes) and from the groundwater (base flow) to the river network, in order to feed the river flow.

 ,QSXWGDWDIRUWKHK\GURORJLFDOVWXG\

6.4.1 Limnimetric data The limnimetric data consist of the water levels observed at nine measuring stations in the catchment area. Each station is representative for the water-outflow of the upstream catchment and can therefore be used to characterise that specific part of the Geul river catchment. Figure 6.1 illustrates the locations of the measuring stations and the corresponding Geul sub-catchment areas.

Hydrological study 66 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Table 6.1 summarises the hourly flow data and indicates whether data are missing. The reader will remark that the data are incomplete for many years. Figure 6.2 shows typical annual flows, measured in different limnigraphic stations.

# Beek

Maastricht airport #

Meerssen # N # Valkenburg Ubachsberg Maastricht # #

# Ransdal l

Simpelveld # # Mar graten # Mol en tak # # Gul pen # # # Partij Hommerich

Ep en Heyenrath # # # Slenaken # Vaal s Cottessen # # # Sippenaeken

Vo er en #

Hombourg # Legend :

Walhorn # # Pl uvi ographs

# Pl uvi omete rs

# Limnigraphs Riverbed WatershedinEys 28.51 km² WatershedinPartij 29.31 km² Wat ershed i n Sl enaken 27.08 km² WatershedinGulpen 0123456789Kilometers + 46.07 km² Wat ershed i n Cott essen 121.70 km² WatershedinHommerich + 149.83 km²

+++ + + Watershedin Meerssen 334.72 km²

UHAGX, FUSAG Gembl oux

Figure 6.1 Sub-catchment areas in the Geul catchment area and associated limnimetric stations, measuring the water flows.

Hydrological study 67 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

The data quality has been assessed as well. As the simulation model requires complete time-series, the missing data were — in some cases — substituted on the basis of a statistical analysis. The results of the data analysis are presented in detail in Annexe D.

Table 6.1 Hourly discharges: available and missing data 6RXUFH 6WDWLRQ          COTTESSEN 84% 0,2% 0,4% 30% 9% 3% 10% 0,7% HOMMERICH 25% 11% 5% 1% 3% 0,3% 2% 2% 1% MEERSSEN 16% 5% 5% X 6% 8% 14% 2% 0,3% :DWHUVFKDSÃ5RHUÃHQÃ2YHUPDDV SLENAKEN 9% X 0,4% 8% X 79% 3% 4% 63% GULPEN 7% 1% 0,8% X 0,4% 11% 5% EYS 53% 0,1% X X X X X 2% PARTIJ 60% 2% 2% 0,1% 6% 5% 0,6% 10% MOLENTAK 75% 0,1% X 0,1% 12% SIPPENAEKEN 45% X X

No data …% = missing data X Complete

*(8/Ã352-(&7ÃÃ(YROXWLRQÃRIÃKRXUO\ÃGLVFKDUJH *(8/Ã352-(&7ÃÃ(YROXWLRQÃRIÃKRXUO\ÃGLVFKDUJH 6WDWLRQÃRIÃ&RWWHVVHQÃ *HXO ÃÃ 6WDWLRQÃRIÃ0HHUVVHQÃ *HXO ÃÃ

24 30 23 29 22 28 27 21 26 20 25 19 24 18 23 V 22  17 V ñ ñ 21 P16 P20 Ã 15 Ã H Ã 19 J 14 H 18 U J 17 D 13 U K D 16 F 12 K V F 15 L 11 LV 14 ÃG G 13 \ 10 Ã UO 9 O\ 12 U 11 X 8 X R R 10 + 7 + 9 6 8 5 7 4 6 5 3 4 2 3 1 2 0 1 0 01/01/93 31/01/93 02/03/93 01/04/93 01/05/93 31/05/93 30/06/93 30/07/93 29/08/93 28/09/93 28/10/93 27/11/93 27/12/93 01/01/97 31/01/97 02/03/97 01/04/97 01/05/97 31/05/97 30/06/97 30/07/97 29/08/97 28/09/97 28/10/97 27/11/97 27/12/97 5HSURJUDSK\ 5HSURJUDSK\ : UHAGx - FUSAG - Gembloux : UHAGx, FUSAG Gembloux

'DWDÃVRXUFH : Waterschap Roer en Overmaas (NL) 'DWDÃVRXUFH : Waterschap Roer en Overmaas (NL)

Figure 6.2 Examples of measured water flow (hourly discharge)

6.4.2 Climatic data The climatic data, which are required as input in the hydrological model, include daily rainfall, hourly rainfall (pluviographs), daily minimum and maximum temperatures and daily hours of sunshine. The Thiessen Method is used for calculating the averaged precipitation

Hydrological study 68 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

6.4.3 Geographic data CSO and HA-FSAGx have assembled GIS map layers of different types of data. These GIS layers were used as input for the simulations, and include: - elevation (Digital Elevation Model or DEM); - land cover (current and historic); - river-network (Geul, Gulp, Eijserbeek, Hohnbach and Selzerbeek); - type of soils. The base maps were moreover used to derive secondary data (also required as input for the hydrological simulations). More details on the available data are given in Annexe D.

 +\GURORJLFDOFKDUDFWHULVDWLRQRIWKH*HXO5LYHUFDWFKPHQWDUHD The hydrological characterisation of the catchment area includes the assessment of the measured data and the analysis of rainfall-distribution in relation to flow characteristic values, measured for the current (reference) situation. The degree of correspondence between the amount of water supply (rainfall) and the amount of water at the outlet is analysed in the section ‘Water balance’. The temporal variability of water flow is analysed in the section ‘Frequency analysis (of peak discharges)’ and is illustrative for the separation of rainfall water into surface water runoff and groundwater base flow. The latter will be explained in the section on hydrogeology (Annexe D, paragraph 1.5.5).

The limited number of meteorological stations, the above-mentioned lack of data for some stations and the rather poor quality of the data hamper a statistical analysis of the reference hydrology. Nevertheless, a preliminary analysis has been performed of which the procedure and results are shown in Annexe D. A summary of the characterisation is given below.

6.5.1 Flood frequency analysis A frequency analysis, based on the Gumbel distribution for maximum discharge values, has been performed for the maximum hourly values measured in the limnimetric stations of Cottessen, Hommerich and Meerssen. The resulting peak discharge values for the different stations are very similar. There is little difference between Meerssen and Hommerich, despite the fact that the catchment area at Meerssen is two times larger than the catchment area at Hommerich.

6.5.2 Characteristic events An analysis has been performed for a selection of peak discharges. The average precipitation in the catchment is calculated at each different limnimetric station. Fast

Hydrological study 69 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas runoff is separated from base flow and the water volumes are calculated in order to determine the runoff characteristics. The results are summarised in Table 6.3

Table 6.3 Calculated flood hydrographs (without base flow) 3UHFLSLWDWLRQ 5XQRII 9ROXPHÃRIÃUXQRII 3HDNÃGLVFKDUJH PP PP ÃPñ PñV

&RWWHVVHQÃÃ NPð dec-94 59 17.9 2.2 19.6 +RPPHULFKÃÃ ÃNPð jan-93 51 12.1 1.8 23.7 sep-93 69 10.3 1.5 20.4 dec-94 54 12.8 1.9 18.2 sep-98 91 21.9 3.3 54.7 *XOSHQÃÃ ÃNPð jan-93 35 3.4 0.2 5.1 sep-93 78 4.6 0.2 3.2 dec-94 49 2.8 0.1 1.4 (\VÃÃ ÃNPð dec-94 34 2.8 0.1 0.9 3DUWLMÃÃ ÃNPð dec-94 35 3.6 0.1 1.7 0HHUVVHQÃÃ ÃNPð jan-93 52 6.1 2.1 23.9 sep-93 70 5.3 1.8 21.5 dec-94 49 6.1 2.0 16.6 sep-98 87 11.6 3.9 39.9 6OHQDNHQÃÃ ÃNPð jan-93 30 5.1 0.1 5.9 dec-94 63 5.8 0.2 1.6 6LSSHQDHNHQÃÃ ÃNPð sep-98 102 19.0 2.1 36.4 HA-FUSAG Gembloux

Two remarkable points can be observed: 1. Despite the catchment area being approximately two times larger at Meerssen than at Cottessen or Hommerich, the peak flows and the flood volumes (surface water runoff related parts) appear not to be proportional to the catchment surface area at Meerssen or Cottessen / Hommerich for each specific rainfall event. For periods with data available at all measuring stations (e.g. December 1994), a relative correspondence can be found between the observed flows of the Geul

Hydrological study 70 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

and the observed flows of the tributaries, giving reasonable water balances. Thus flow data are somehow questionable, but not in totality. 2. The calculated runoff coefficients at Cottessen reach up to 25 or 30% for major rainfall events, which is a low value, but quite normal for the Geul basin. The calculated runoff coefficients at Meerssen are lower than 15% for major rainfall events, which is DEQRUPDOO\ low. This could perhaps be due to the poor quality of the data.

6.5.3 Waterbalance of the catchment area The annual average rainfall for the period 1993-1998 and the measured runoff is summarised for each sub-basin in Table 6.4.

Table 6.4 Measured (“Meas.") or simulated (“Sim.") mean annual balances (1993-1998) (PLVVLQJGDWDDUHFRPSOHWHGE\WKHQHLJKERXULQJVWDWLRQVLIQRWWRRVFDUFH)

6WDWLRQ 0HDVÃPHDQ +HLJKWÃRIÃDQQXDO 0HDVÃYROXPHÃRI 0HDQÃDQQXDOÃUXQRII SUHFLSLWDWLRQ UXQRII DQQXDOÃUXQRII FRHIILFLHQW PP PP P È 0HDVÃÃÃÃÃÃÃÃÃÃÃ6LP 0HDVÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ6LP

Cottessen (122 km²) 947 (375) (1) 316 (47,5) (39) 33

Hommerich (150 km²) 938 319 311 47,5 34 33

Gulpen (46 km²) 949 255 357 11,2 27 38  Eys (29 km²) 864 132 299 3,8 15 35

Slenaken (27 km²) 1037 296 393 8,0 28 38 

Partij (29 km²) 897 171 315 4,9 19 35

Meerssen (341km²) 902 275 305 93,8 30 34

HA-FUSAG Gembloux (1) missing data are numerous (see Table 6.1)

For all the tributaries of the Geul river, but not for the Geul itself, one can observe low to very low annual runoff coefficients.

Hydrological study 71 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

The water balance in these catchments seems to indicate water losses. The poor quality of limnimetric data at the measuring stations of Partij and Eys, makes it impossible to conclude on this topic for the Eyserbeek and Selzerbeek. However, it appears that water losses do occur in the Gulp catchment, for which limnimetric data are satisfying. These water losses can be caused by groundwater flows.

The altitude of the Gulp river is higher than the altitude of the Meuse river (see Figure 6.3), inducing a gradient from the Gulp to the Meuse. In permeable rocks, like the Cenozoic and Mesozoic formations present in the basin, this gradient may be the origin of groundwater flows from the Gulp basin to the alluvial plain of the Meuse river (Fig. 6.3).

Figure 6.3 Groundwater circulations from the Gulp river basin to the Meuse river basin

 0RGHOGHYHORSPHQW

6.6.1 Description of the model The integrated hydrological model MOHICAN - in the version used for this present study - simulates the water profile in the soil, the fluxes of water from soil to groundwater and the transfer from soil water and groundwater to the river network. The model is composed of a soil sub-model, a groundwater sub-model and a master code, which

Hydrological study 72 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas controls the running of the sub-models, ensures synchronisation and calculates the transfers of water-fluxes.

6.6.1.1 Soil sub-model EPIC-GRID The catchment area is subdivided into medium-sized grid cells (1kmx1km). Each grid- cell is divided in several non geo-referenced units, regarding land cover, crop types, slope gradient and soil type, as provided by the database in the format of GIS map layers. The main processes simulated by the soil sub-model EPIC-GRID are: - infiltration; - evapo-transpiration; - snow accumulation / melting; - overland flow; - rapid and slow hypodermic flow ; - percolation to the groundwater; - variation of soil humidity.

The principal results (water-fluxes) are: - overland flow (hourly); - rapid hypodermic flow (hourly); - slow hypodermic flow (daily); - percolation flow (daily).

6.6.1.2 The groundwater sub-model The soil sub-programme EPIC calculates the water flow, percolating from the soil into the saturated groundwater zone. Its temporal transfer function and the geographical discharge zones are determined by the groundwater sub-programme, using respectively deconvolution operations and hydrogeological data (see Annexe D).

6.6.1.3 The master code The water flow from both the soil and the groundwater compartments to the river network is calculated by the following procedure: 1. The ‘inter-cell’ transfer time (from a given grid-cell to another grid-cell) is computed for the overland and hypodermic flows. It is calculated as a function of

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the soil surface water storage capacity, which is function of the soil surface roughness and of the slope. 2. The transfer time from the cell to the river network is calculated as a function of the distance cell-river, and depends also on the slope and the roughness of the soil.

6.6.2 Schematisation of the catchment The schematisation of the catchment for the hydrological modelling consists of two phases: - the preparation of the maps that will be used as input data; - the introduction in the programme of all parameters corresponding to the different classes distinguished in the input-maps. (For more details and maps: see Annexe D.7)

6.6.2.1 Preparation of the spatial data The sub-catchments were defined based on the DTM and the demands for the hydrodynamic simulation. They are demarcated in Figure 6.1. The hydrological model calculates an outflow hydrogramme at the downstream end of each sub-catchment. The characteristics of the sub-catchments were derived from the following GIS map layers: - Digital Terrain Model (Map 4.2); - Slope map (Map 4.3); - Current land use map (Map 4.4); - Soil maps: - texture - depth - percentage coarse fragments - hydrological soil groups (see Figure 6.4 - Infiltration capacity of the soils decreasing from A to C, risk of runoff increasing - SCS method from the US Soil Conservation Service - details are given in Annexe D.)

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Figure 6.4 Hydrological soil groups (infiltration capacity decreasing from A to C, risk of runoff increasing), derived from the SCS (Soil Conservation Service of the US) soil map.

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6.6.2.2 Determination of initial parameters The soil sub-programme (EPIC-GRID) needs a number of parameter values in order to calculate the different water fluxes for the different types of land use and soils. Most of these values have been obtained from reference tables: EPIC bibliography and regional information concerning agricultural practices and crops parameters (for instance LAI and others), SCS tables and Brakensiek tables. Among the most important parameters are the so-called ‘CN parameters’ (SCS method), which are a function of the vertical soil humidity profile (daily calculated in the model). In Annexe D, some maps are presented, showing the CN runoff parameters and thus providing an indication on the spatial repartition of the risk of runoff (the SCS risk of runoff, which is a function of land use, soil type, slope and soil humidity characteristics).

The groundwater sub-programme requires transmissivity values to calculate the groundwater flow. These values depend on the characteristics of the geological layers. In Annexe D, values are given for the different geological formations of the Geul hydrogeological basin.

 0RGHOYDOLGDWLRQ

6.7.1 Selection of the simulation period Most of the available rainfall and flow data cover the period 1989-1998. This 10-years period was therefore chosen for validating and running the hydrological model. However, from this period, 4 years (1989-1992) are needed for the initialisation of the groundwater and soil modules. Consequently, the HIIHFWLYH simulation period covers the period January 1993 to December 1998 (6 years). This period includes the recent major flood events in the Geul basin (notably January 1993, September 1993 and September 1998).

The hydrological model requires no calibration. The model is validated on the five major flood events that occurred during the period 1993-1998: - January 1993 (day 10 to 15); - September 1993 (day 267 to 270); - December 1994 (day 360 to 365); - September 1996 (day 240 to 245); - September 1998 (day 254 to 260).

,WPXVWEHQRWHGWKDWHDFKRIWKHVHIORRGHYHQWVLVQRWFRPSOHWHO\PHDVXUHG WKHUDLQIDOO DQGULYHUIORZPHDVXULQJVWDWLRQVSURYLGHRQO\LQFRPSOHWHGDWDVHWV 

Hydrological study 76 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Figure 6.5. Simulated and observed water discharges at three measuring stations - -DQXDU\

6.7.2 Results of the validation The effective hydrological simulation is performed on the period 1991-1993 (hourly time step for the calculation of the runoff component).

The results of the hydrological modelling (calculated water production to the river network at three limnimetric stations) are presented for typical flood events: - flood event of January 1993 (days 10 to 15): Figure 6.5. - flood event of December 1994 (days 360 to 365): Figure 6.6. - flood event of September 1998 (days 254 to 260): Figure 6.7.

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Figure 6.6. Simulated and observed water discharges at three measuring stations - 'HFHPEHU

A detailed analysis of the results of the hydrological modelling shows: - a good agreement between the observed and the simulated values of the flow regime for the upstream part of the Geul catchment (upstream Cottessen) and for the downstream part of the Geul (Meerssen); - a significant lowering of the peak of the flood and a lag in phase (about 12 hours) of the flood at Meerssen; - a good agreement between the observed and the simulated water balances of the Geul river flow at Meerssen (335 km2), the outlet of the basin (see Figure 6.8, results obtained for a representative and reliable year, 1993); moderate good results are obtained at Cottessen (122 km2) and Hommerich (150 km2); - differences in the water balances (observed and simulated) for the Gulp river (see Figure 6.8), probably due to groundwater losses from the Gulp river/basin to the alluvial plain of the Meuse river (see § 6.5.3 and Figure 6.3); the same differences in the water balances (observed and simulated) for the Eijserbeek and the Selzerbeek

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(see Figure 6.8), but these differences are not significantly established, owing to the poor quality of the available flow measurement data.

Figure 6.7. Simulated and observed water discharges at three measuring stations - 6HSWHPEHU

6.7.3 Conclusions of the validation The conclusions based on the validation results are the following: - the hydrological model is able to simulate and reproduce the hydrological behaviour of the watershed, including groundwater transfers; - up to now, the hydrological model has not included any modelling of water losses from the Gulp catchment (groundwater fluxes from the Gulp river to the alluvial plain of the Meuse river); additional data must be collected to state this process more precisely;

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- the differences between the observed and simulated peak values of the Geul river flow during flood events have to be interpreted as the effect of water surface flow processes (described by the hydraulic model, see Chapter 7).

*HXOÃ%DVLQ

3.50 3.18

3.00 2.91 Yearly Mean Flow - Simulations (m³/sec) Yearly Mean Flow - Observations (m³/s) 2.50

2.00 1.67 1.57 1.47 1.50 1.27 1.07 1.00

0.47 0.50 0.37 0.31 0.29 0.23 0.22 0.14 0.11

0.00 Meerssen Cottessen Hommerich Molentak Slenaken Gulpen Partij Eys

Figure 6.8 Observed and simulated water balances for eight measuring stations

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6.8.1 Scenarios The following land use scenarios, which were developed in Chapter 5, are used in the hydrological simulations: 1. Current land use (Map 4.4 in Chapter 4); 2. Transformation of cultivated farming land with slope higher than 12% into pastureland (see Figure D.8.3 in Annexe D); 3. Transformation of farming - and pastureland with slope higher than 10% into forest (see Figure D.8.4 in Annexe D); 4. Transformation of all farming land into farming land with green belts (see Figure D.8.5 in Annexe D);

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5. Land use map of 1950's (see Figure D.8.2 in Annexe D).

As explained in Chapter 5, only part of the management measures proposed in the scenarios can be simulated with a hydrological model (land use related measures). Land use changes appear in each of the five chosen scenarios. Therefore, for each scenario, specific maps have to be prepared. This leads up to five different modelling operations and five sets of simulation results. Table 6.5 presents the land use distribution according to the various scenarios. It must be noted that all scenarios are derived from the current land use map.

Table 6.5 Land use distribution according to the various scenarios /DQGXVHÃRIÃWKHÃ*HXOÃULYHUÃFDWFKPHQWÃDWÃ0HHUVVHQÃDFFRUGLQJÃWRÃWKHÃVFHQDULRV

&ODVV &XUUHQWÃODQGXVH /DQGXVHÃRIÃ /DQGXVHÃVFHQDULRÃ/DQGXVHÃVFHQDULRÃ /DQGXVHÃVFHQDULRÃ (Agriculture with slope > 12% (Agriculture and grassland (Greenbelts) = Grassland) with slope > 10% = Forest) km² % km² % km² % km² % km² % Weeded crops 32.97 9.7 17.33 5.1 31.03 9.1 29.42 8.6  4.8 Non weeded crops 26.43 7.8 53.66 15.7 24.07 7.1 22.77 6.7  3.9 Water 0.16 0.0 0.41 0.1 0.16 0.0 0.16 0.0 0.16 0.0 Deciduous forest 43.48 12.8 0.0 43.48 12.8 43.48 12.8 43.48 12.8 Resinous forest 6.62 1.9 0.0 6.62 1.9 6.62 1.9 6.62 1.9 Buildings in agricultural area 3.26 1.0 8.24 2.4 3.26 1.0 3.26 1.0 3.26 1.0 Buildings in rural area 1.22 0.4 0.0 1.22 0.4 1.22 0.4 1.22 0.4 Urban area 14.77 4.3 0.66 0.2 14.77 4.3 14.77 4.3 14.77 4.3 Grassland 187.07 54.9 159.89 46.9  56.3 156.09 45.8  64.5 Orchard 5.73 1.7 52.31 15.3 5.73 1.7 5.73 1.7 5.73 1.7 Main roads / railroads 8.89 2.6 0.0 8.89 2.6 8.89 2.6 8.89 2.6 Weeded / non weeded crops (mixed) 6.51 1.9 5.01 1.5 6.02 1.8 5.63 1.7  1.0 Deciduous / resinous forest (mixed) 3.88 1.1 43.44 12.7 3.88 1.1  12.6 3.88 1.1

7RWDO     

Faculté Universitaire des Sciences Agronomiques de Gembloux Unité d'Hydraulique Agricole Prof. Mme S. Dautrebande Ir. D. Deglin Sept. 1999

In scenario 2 only the steeper slopes, above 12% and currently used for agriculture, are transformed into grassland. This measure affects only 4.8 km2 in the total catchment, of which 1.9 km2 of weeded crops, 2.4 km2 of non-weeded crops and 0.5 km2 of mixed crops. The total area involved covers about 1.4% of the total catchment area. In scenario 3 all slopes steeper than 10%, currently cultivated or in pasture, are afforested. This afforestation covers an area of 39,1 km2, of which 3,5 km2 is currently used for weeded crops, 3,6 km2 for non-weeded crops, 31 km2 as grassland and 1 km2 for mixed crops. The total area is vast and represents 11.5% of the total catchment area. Scenario 4 assumes that the planting out of green belts2 in parcels of (cultivated) farmland will influence 50% of the agricultural area. This has a major impact on the cultivated acreage and increases the grassland area with 33 km2 or 9.6% of the total catchment area.

2 Green belts are grass strips of several meters width along a contour line, interrupting the parcel length.

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For the current land use and the 1950 land use scenario, the land use maps have been based on maps and satellite imagery.

6.8.2 Results As mentioned in paragraph 6.6.3.1, the hydrological simulations are done for the complete period 01/01/1991-31/12/1998 (calculation of the runoff component at hourly time steps). From this period, only the years 1993 and 1998, which are the more reliable, are used as results and analysed. The analysis is based on the comparison of the maximum discharges at the limnimetric stations.

Figure 6.9 shows the calculated results of the total water production to the river network of the river basin at Meerssen (outlet of the Geul basin) for each simulated scenario, corresponding to the flood event of -DQXDU\ , and the comparison with the "reference" scenario (current situation). The observed discharge at Meerssen during this flood event is also plotted on this figure.

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Figure 6.9 Results of the simulation of all scenarios, compared to the current scenario - Total water production to the river network of the river basin at Meerssen - )ORRGHYHQWRI-DQXDU\

Figure 6.10 presents the calculated results of the total water production to the river network of the river basin at Meerssen (outlet of the Geul basin) for each simulated scenario, corresponding to the flood event of 6HSWHPEHU and the comparison with the "reference" scenario (current situation). The observed discharge at Meerssen during this flood event is also plotted on the figure.

Figure 6.10 Results of the simulation of all scenarios, compared to the current scenario - Total water production to the river network of the river basin at Meerssen - )ORRGHYHQWRI6HSWHPEHU

The results of the different scenarios show little difference on the total water production fluxes. As these results reflect the implementation of the hydrological (environmental- friendly) measures only, a relative comparison may be made. In general it can be stated

Hydrological study 83 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas that scenario 3 (transformation of farming - and pastureland with slope higher than 10% into forest) and land-oriented measures of scenario 4 (transformation of all farming land into farming land with green belts) show the highest improvements by giving a maximum daily water flux reduction. In the case of high rainfall events, such as the rainfall event of September 1998, scenario 3 shows a reduction of about 7% of the maximum hourly water flux to the river network; and the land-oriented measures of scenario 4 show a reduction of about 9% of the maximum hourly water flux to the river network. In the Geul river catchment, scenario 3 (transformation of farming - and pastureland with slope higher than 10% into forest) and the land-oriented measures of scenario 4 (transformation of all farming land into farming land with green belts) show more or less the same results as the simulation of the 1950’s.

The expected effects of these measures however remain small, owing to the relatively small surface area involved in the modifications (cf. Fig. 1.2 about the effect of increasing urbanisation) and the low runoff coefficients observed under the current situation (cf. hydrological analysis). As regards the long-term ZDWHUEDODQFH, the results of the simulation of all scenarios, compared to the "reference" scenario (current situation), are shown in Figure 6.11 (long term averaged water production at each limnimetric station - m3/s - over the total period 1993-1998). The observed values of the water discharge at these stations, if available, are also plotted on this figure. These results show a small effect of the proposed measures on the long-term water balance (small reduction of the mean water discharge, less than 6%).

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*HXOÃ%DVLQ &RPSDULVRQÃRIÃ6LPXODWLRQV 0HDQÃ)ORZÃ PñV ÃÃ3HULRGÃ 3.50 Simulation GE1: Current land cover Simulation GE2: Agriculture areas with slope > 12% --> Pasture/Grassland 3.00 Simulation GE3: Agriculture and Pasture areas with slope > 10% --> Forests Simulation GE4: Agriculture areas --> Agriculture areas with greenbelts Simulation GE5: Land cover of 1950 2.50 Observations (mean 1993-1998)

2.00

1.50

1.00

0.50

0.00 Meerssen Cottessen Hommerich Molentak Slenaken Gulpen Partij Eys

Figure 6.11 Long-term water balance of all scenarios compared to the "reference" scenario. Mean water flow (m3/s), period 1993-1998. The final output of the hydrological model MOHICAN is the water flux, at each time step, flowing to each river segment. This lateral water inflow (m³/sec) feeding the river stream is calculated along the river profile for some hundreds of locations (nodes), which are obtained by discretisation of the river network. Within this set of discretised points, about thirty nodes are selected, where the hydrological model has to deliver water-fluxes to the hydraulic ISIS model.

 &RQFOXVLRQV The hydrological study presented in this chapter aimed at the quantification of the water inflow into the Geul river system under various situations and scenarios. The output of the hydrological modelling is also to be used as input to the hydrodynamic study (see Chapter 7). The water inflow is simulated as a function of the soil and environmental variables characterising the uplands of the Geul catchment area. They include climate, topography, soil and subsoil characteristics, hydrogeology and land use. The model proves to be capable simulating the hydrological behaviour of the Geul basin under the current situation. As the hydrological model is using physically-based

Hydrological study 85 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas representations and has not been calibrated (specifically) for the Geul basin, it has been concluded that the model is able to simulate the runoff and the base flow for different land use classes and able to estimate the effects of changes in land use or agricultural practices. Uncertainties, however, remain in the hydrological simulation results, associated with probable losses of groundwater from tributaries of the Geul to the alluvial plain of the Meuse river.

Three main scenarios with different land use types are studied, reflecting the effects of possibly applicable environmental measures to reduce the (flash) flood events. These scenarios consider respectively all steep slopes covered with grassland, all steep slopes covered with forest and all agricultural fields protected by green belts or hedgerows. Besides these three scenarios, two reference situations are studied as well, namely the current and the historic situation, characterised by the current and historic (1950's) land use. The simulated water inflow, derived from runoff, shows important peaks in time, related to high rainfall events. From the results of the various simulated scenarios, it can be concluded that the proposed environment-friendly measures could reduce, but only weakly, the peak water fluxes under high rainfall events.

 5HFRPPHQGDWLRQV Despite the fact that their effects remain rather small (less than 10% of the hourly peak water fluxes to the river network under high rainfall events), land-related measures such as transformation of farming- and pastureland with slope higher than 10% into forest or transformation of farming land into farming land with green belts, appear to contribute to the reduction of peaks of water fluxes in the Geul catchment. It is thus recommended to take into account these environmental-friendly orientations. Moreover, a complementary effect on the peak discharge can be obtained with measures to be taken in the river itself (see Chapter 7).

Considering the results obtained during the present hydrological study, it is also recommended: - to increase the availability and reliability of the data (rainfall, river discharge, characterisation of urban areas); - to investigate by additional measurements and specific hydrogeological studies the question of possible direct losses of groundwater from the Geul catchment to the alluvial plain of the Meuse;

It is also recommended to specifically address, in a future study, the problem of soil erosion in the Geul river catchment (and not only in relation to (large) flood events).

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 $FNQRZOHGJHPHQW The ULg and FSAGx acknowledge the Ministry of Equipment and Transport (MET) of the Walloon Region for giving the authorisation to utilise the MOHICAN model (partim hydrology) in the scope of the present study.

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 +<'52'<1$0,&678'<

 ,QWURGXFWLRQ This chapter describes a hydrodynamic study of the Geul river system. The results reflect the dynamics of the water flow through the Geul river and its tributaries. The dynamical flow is simulated on the basis of the results generated in the hydrological study of Chapter 6. These results include the volume and speed of water flowing into the Geul river and its four tributaries, generated for about thirty locations, also called “ISIS nodes”, along the Geul river system. The water inflow rates were simulated by the hydrological MOHICAN programme (ULg and FSAGx) as a function of the hourly variability of weather, of topsoil and subsoil characteristics and of the land use scenarios defined. The ISIS Flow model is used in the present chapter to simulate the water heights and water volumes per second running through the Geul river and its tributaries. The results per scenario are presented as a hydrograph. They are illustrating the amounts of river water passing through a certain location throughout time, making peaks in river water discharge easily detectable. Results are also presented as maximum water heights along the longitudinal profile of the Geul river system, indicating whether and where the water height exceeds the height of the bordering river banks and consequently, whether and where flooding may be expected. The longitudinal profile is attached in Annexe G. The scenarios defined in Chapter 5 include two scenarios with measures for water retention devices in the upstream river channel.

Section 7.2 presents the specific objectives of the hydrodynamic study and Section 7.3 presents the study approach. Technum and its subcontractor IMDC used the modelling package ISIS Flow to model the Geul river system. This modelling is briefly described in Section 7.4, including a brief description of the modelling package ISIS Flow, the model set-up of the Geul river and its tributaries, and the calibration and verification of the modelled Geul river system. The reader is referred to Annexe E for a more detailed description of these sections. Section 7.5 describes the simulations; paragraph 7.5.1 provides some details about the scenarios defined and paragraph 7.5.2 describes the results of the simulations performed for the 5 scenarios. The conclusions are presented in Section 7.6.

The scenarios defined in Chapter 5 include both environmental (land use) measures and hydrodynamic measures. The latter include: 1. the introduction of constriction devices that create additional storage on locations where it is allowed; 2. the increase in the roughness of the floodplain, for instance, by the introduction of dense bushes.

It was concluded in Chapter 6 that land use changes did not lead up to significant differences in simulated water inflow rates (less than 10% on hourly peak values).

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Hydrodynamic simulation led to similarly insignificant effects of water inflow rates on river water discharges and river water heights, but led to significant effects of the installation of hydraulic devices in the upstream river canal.

 2EMHFWLYHV The hydrodynamic study identified the following objectives: • Simulation of the water flow through the Geul river system • Analysis of the impact of the different scenarios on peak discharges and water levels • Identification of the flood-prone areas

 $SSURDFK The researchers of Technum and IMDC followed a well-structured procedure throughout the modelling study to assure maximum quality of the results, namely realistic simulations of water movement, of water discharge levels and of water levels. The simulations were performed in accordance with the five steps defined below:

• Data collection The input for the model consisted of two different types of data: the topology and the boundary conditions. The topology defines the objects in the river model and where these objects are located relative to each other. The objects defined in this study include bridges, sluices, river cross-sections and other infrastructure. The boundary conditions are set by the amounts of water inflow into the river, as was measured and simulated (in Chapter 6) at several locations along the Geul river (hydrogrammes and hydrographs).

• Set-up of the model schematisation The input of the topological data into the modelling package created a schematised representation of the Geul river system, or, a model. The model is like a geographical map, representing the location, widths and depths of the Geul river and its tributaries as well as the location of all types of infrastructure devices in the river channel.

• Calibration The ISIS model of the Geul river system was calibrated in order to generate realistic simulation results. The calibration included the simulation of water flow for a well-defined situation with available measurements of water discharge, followed by a comparison of the simulated and measured water discharges. The value of coefficients was adjusted till the simulations fitted the measurements. The calibration took place with data from

Hydrodynamic study 89 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas several measuring stations for high water periods. The calibration and model outcome were verified with input of another high water period. • Simulation The Geul river water flow was simulated for each scenario, after the above-described preparatory steps were made. Time periods were selected and the associated weather data were the input to simulate the river water discharges and -heights for several locations along the Geul river. This was done for each scenario and the results were plotted on a longitudinal profile of the Geul river.

• Analysis The simulation results were analysed and the differences among the scenarios were compared for some selected locations along the river. The comparisons were described.

 0RGHOOLQJRIWKH*HXODQGLWVWULEXWDULHV The reader is referred to Annexe E for a more detailed description of the technical modelling aspects.

7.4.1 The ISIS modelling package The ISIS Flow programme computes flow depths and discharges using a method based on the equations for shallow water waves in open channels, the “de Saint Venant equations”. Internal boundary conditions in the ISIS Flow package include a wide range of hydraulic structures. The hydraulic structures and units used in the hydrodynamic modelling of the Geul river system include the following: - River - Interpolate - Conduit - Culverts - Junctions - Bridges - Weirs and spills - Orifices - Sluices - QTBDY - QHBDY

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These hydraulic structures are described in Annexe E.

7.4.2 Model set-up This section describes the set-up of the hydrodynamic model for the Geul river.

7.4.2.1 Topological discretisation The model is built for the Geul river and its main tributaries, namely the Gulp, the Eijserbeek and the Selzerbeek as well as for two smaller tributaries, the Kleine Geul and the Geulke and two 'natural weirs'. Additionally, three canals supplying water to mills were included in the model. Note that only the Dutch tributaries were considered, due to a lack of data on river cross-sections in the Belgian part. The Geul river itself was modelled from the junction with the Hohnbach down to the measuring station at Meerssen. Table 7.1 lists the river branches included in the model with their total length. A schematic overview of the hydrodynamic model is given in Figure 7.1. In Annexe E, the reader will find a more detailed representation (Figures I, II, III, IV).

Table 7.1 River branches included in the hydrodynamic model. Branch Modelled length Geul (Belgian part) 10.780 m Geul (Dutch part) 33.895 m Gulp (Dutch part) 8.960 m Selzerbeek (Dutch part) 12.000 m Eijserbeek (Dutch part) 9.430 m Geulke 2.500 m Kleine Geul 1.600 m Geulhemermolen 561 m Oude Molen and Franse Molen 656 m Onderste Molen 372 m

7.4.2.2 Hydraulic structures Hydraulic structures in and along the river branches, like bridges and sluices, may importantly affect the water flow. Both fixed and adjustable hydraulic structures were modelled. Fixed structures were all modelled as 'weir-units'. Table 7.2 gives an overview of the most important modelled structures (considered as fixed). Sluice units were used whenever the structure was regulating flow conditions. Table 7.3 lists these regulating structures. The table also mentions on what basis these structures are regulated.

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Figure 7.1 Schematic overview of the set-up of the model for the Geul river system

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Table 7.2 Structures modelled as fixed weirs. Number Branch Description 1 Onderste Molen Inlet sluice, Onderste Molen 2 Oude Molen and Franse Molen Mill sluice and outlet sluice Franse Molen 3 Geul Weir at Volmolen 4 Geul Weir at Epermolen 5 Geul Embankment between Geul and water supply canal of Wijlre 6 Kleine Geul Gated sluice 7 Geulke Oliemolen 8 Geulke IJzermolen 9 Geulhemermolen Outlet sluice of Geulhemer mill 10 Oude Molen Mill sluice Oude Molen 11 Geul Weir at Bovenste Molen 12 Geul Fish ladder at Onderste Molen 13 Geul Weir at Onderste Molen 14 Geul Side spill at Schaloensmolen 15 Geul Weir at Kruitmolen 16 Geul Concrete sill near Geulke 17 Geul Bottom drop at Meerssen 18 Geulke Stop block weir 19 - 'natural weir' between Geulke and Kleine Geul

Table 7.3: Regulating structures modelled as gated sluices. Number Branch Description Controlled by: 1. Onderste Molen Outlet sluice Upstream water level 2. Oude Molen/ Franse Molen Outlet sluice Discharge at Cottessen 3. Geul Weir at Epermolen Discharge at Cottessen 4. Geul Walramstuw Upstream water level 5. Geul Weir at Groote Molen Upstream water level

Hydrodynamic study 93 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

7.4.2.3 External boundary conditions To run a hydrodynamic model, two types of boundary conditions are required, i.e. upstream and downstream boundary conditions. The downstream boundary condition is the rating curve of the measuring station in Meersen (QHBDY unit). The results of the hydrological modelling are the upstream boundary conditions (QTBDY unit). The hydrological results are distributed over the hydrodynamic model in 28 different model points (see schematic representations, Figures I to IV, in Annexe E). Thus the land use dependent water inflow, simulated in Chapter 6, was determinant for the hydrodynamic simulation of the amounts and timing of water flowing through the Geul river.

7.4.3 Calibration and verification of the model In the numerical model of the Geul river system, as it is described up to now, two uncertainties still exist: general head losses and specific head losses. Head losses signify the difference in height (m) between the water level of a downstream location and the water level of an upstream location at a given moment. General head losses refer to the ‘natural’ gradient of the river itself, and are a function of the roughness coefficient of the riverbed and the floodplains. The specific head losses refer to the artificial gradient in hydraulic structures like sluices and are a function of the discharge coefficient at weirs, sluices etc. These uncertainties or unknowns can be partly eliminated by calibrating (and verifying) the model results to measured values. For this calibration and verification the measurements of the following stations can be used: • Partij • Gulpen • Slenakerbrug • Eijs • Cottessen • Hommerich The measurements of the station at Meerssen cannot be used for calibration/verification, because they are used as the downstream boundary condition.

Normally a hydrodynamic model is calibrated by comparing the calculated and measured water levels. Because uncertainties exist on the hydrological input data (discharges), it was preferred to compare calculated and measured rating curves (communicated by the Waterboard Roer & Overmaas). Rating curves were calibrated on the basis of rainfall data as input data, and water discharge measurements as comparative data. Calibration was done on the period of September 24 to October 19, 1993. Verification was done on the high water period of September 7 to November 29, 1998.

Hydrodynamic study 94 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Figure 7.2 shows an example of the fitting between calibrated and ‘measured’ rating curves (measuring station at Hommerich). (see also Annexe E.1)

94.4

94.2

94.0

93.8

3 93.6 $ 1 Ã 93.4 P Ã K 93.2

93.0

92.8

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92.4 0 5 10 15 20 25 30 35 40 4Ã PV Figure 7.2 Calculated and 'measured' rating curves for the measuring station at Hommerich. Calibrated values 1993.

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7.5.1 Description Once the hydrodynamic model had been set up, calibrated and verified, it can be used to simulate the impact of different flood reducing measures in the river and river catchment. Five different scenarios were modelled (see Chapter 5). The current situation, which has been used for the calibration and verification, will be used as a reference. This situation is called scenario 1. An overview of the different scenarios is given in Table 7.4.

Table 7.4 Overview of the scenarios, developed in Chapter 5 Scenario Hydrological part Hydrodynamic part 1. Present land use Actual situation 2. Grass on slopes >12% Increased roughness of the flood plains 3. Forest on slopes >10% Actual situation 4. Greenbelts Addition of 2 constriction devices 5. Land use of the 50's Actual situation

Hydrodynamic study 95 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

These scenarios differ because the hydrological part (land use changes) and/or the hydrodynamic part of the river and its catchment have been changed. Changes in the hydrological part are described in Chapter 6. These changes can be accounted for in the hydrodynamic model by changing the external boundary conditions (see § 7.4.4). In addition two hydrodynamic changes have been considered:

1. Increased roughness of the flood plains: the Manning roughness coefficient of the flood plains is increased from 0.050 to 0.090 sm-1/3. The first value corresponds to the actual situation, i.e. grass and scattered brush, whereas the last value corresponds to the roughness of medium to dense brush. A higher Manning roughness coefficient reflects slower water flow. This hydraulic proposition is part of scenario 2, together with the environmental measure to introduce grassland on all slopes steeper than 12%. 2. Construction of two constriction devices: at labels GEUL16650 and GEUL26650 (for the location of these labels: see the table of the longitudinal profile in Annexe G) two constriction devices are added. The location of these structures has been chosen in such a way that upstream of these structures a large amount of water can be stored without severe nuisance for humans and environment. The constriction devices are modelled here using ORIFICE units, but also other types of constriction devices (pipes, weirs…) are possible. The dimensions of these ORIFICE units have been chosen so that the largest peaks are diminished without creating a backwater effect of more than 2 meters. The dimensions are BxH=3x2 m2 and 4x2 m2 for labels GEUL16650 and GEUL26650 respectively. This hydraulic proposition is part of scenario 4, together with the environmental measure to re-introduce greenbelts or hedgerows.

The five management scenarios have been simulated for three continuous periods. These periods have been chosen in such a way that they contain the most important flooding events. 1. 93a: from 11/01/1993 20h00, to 14/01/1993 23h00 2. 93b: from 25/09/1993 10h00, to 28/09/1993 20h00 3. 98: from 13/09/1998 00h00, to 22/09/1998 09h00

7.5.2 Results The simulation results of these five scenarios are presented in three different ways: 1. Tabular overview of the simulated maximum discharges (volumes per second) and water levels (m) for the five scenarios in selected locations along the Geul river for the periods 93a (Table 7.5), 93b (Table 7.6) and 98 (Table 7.7). For a description of the different labels used in these tables, the reader is referred to Table 7.8. The change in water discharge and water level, relative to the present situation (reference scenario 1), is given between parentheses.

Hydrodynamic study 96 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

2. Hydrographs for the five scenarios near the outlet of the hydrodynamic Geul river model (Geul at Meerssen) for the periods 93a, 93b and 98 (Figures 7.3, 7.4 and 7.5), indicating the timing of water discharge. 3. Maximum water levels of the five scenarios plotted in a longitudinal profile of the Geul for the period 93b. The longitudinal profile is attached to the report as a large sized paper map (Annexe G).

When analysing these results, the following conclusions can be made: • When looking at the maximum water levels in the longitudinal profile (Annexe G) and comparing them to the bank levels, one can see that the major flooding problems occur upstream of the mills: Volmolen, Epermolen, Bovenste Molen, Wijlre, Oude Molen, Franse Molen and Groote Molen. Other problem areas are the Geul river in Wallonia, near the Dutch border, and the Geul river at the mouth with Eijserbeek and Gulp. • When comparing the maximum discharges and maximum water levels simulated for the current and historical situation (scenarios 1 and 5 respectively) in Tables 7.5 to 7.7, one can see that flooding problems have increased significantly during the last 40 years due to changes in land use. For the high rainfall events of 1993 the maximum water levels in the Geul have increased by 5 to 15 cm. The discharges have increased by 2 to 15%. These differences between the present land use and the land use of the 1950’s are more pronounced for the high rainfall events of 1993 than for the high rainfall event of 1998, because in the former ones the upstream catchments are contributing relatively more to the total discharge. • The situation can be improved by changing the land use again. When the steepest slopes are covered with grass (scenario 2) only small improvements can be noticed, even if the roughness of the flood plains is increased. When the steepest slopes are covered with forest (scenario 3) or when greenbelts are used (land-related measures of scenario 4), the situation improves and reaches more or less the situation of the 1950’s. • A significant improvement in the downstream part of the Geul can be achieved by implementing scenario 4. It includes the re-introduction of green belts or hedgerows, combined with the construction of constriction devices (like orifices, pipes…) in the upstream part of the Geul river canal, given the fact that enough space is available to temporary store a large volume of water. Indeed it can be seen in Figures 7.3 to 7.5 that the large peak flows downstream of these constructions are attenuated and delayed. Upstream of these constructions maximum water levels rise over a length of approximately 2 and 1 km. The maximum rise amounts to 2.4 meter (see Table 7.6 at label GEUL16550). By comparing Figure 7.3 with the Figures 7.4 and 7.5, one can see that the constriction devices as they have been implemented into the model now, have almost no influence on the peak discharges lower than 30 m3/s.

Hydrodynamic study 97 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Table 7.5 Maximum discharges and water levels at some points in the studied catchment for the 5 scenarios for the first peak of the period 93a, 11/01/1993 20h00 to 14/01/1993 23h00. Between brackets the difference with the reference situation /DEHO VFHQÃ VFHQÃ VFHQÃ VFHQÃ VFHQÃ

P275 4.93 4.91 (-0.02) 4.70 (-0.23) 4.66 (-0.27) 4.87 (-0.06)  Ã  Ã  Ã  Ã 

GEUL02800 5.85 5.77 (-0.08) 5.57 (-0.28) 5.51 (-0.34) 5.80 (-0.05)  Ã  Ã  Ã  Ã 

GEUL03550 6.39 6.32 (-0.07) 6.11 (-0.28) 6.09 (-0.29) 6.37 (-0.01)  Ã  Ã  Ã  Ã 

GEUL12150 19.63 19.49 (-0.14) 18.73 (-0.90) 18.33 (-1.30) 17.57 (-2.06)  Ã  Ã  Ã  Ã  GEUL16550 20.47 20.32 (-0.15) 19.45 (-1.03) 19.07 (-1.41) 18.26 (-2.21)  Ã  Ã  Ã  Ã 

GEUL26450 24.35 24.17 (-0.18) 22.97 (-1.38) 22.51 (-1.84) 21.55 (-2.80)  Ã  Ã  Ã  Ã 

GEUL31250 20.59 20.62 (0.03) 19.81 (-0.78) 19.24 (-1.35) 18.81 (-1.78)  Ã  Ã  Ã  Ã  GEUL33605 26.29 26.15 (-0.14) 24.88 (-1.41) 24.19 (-2.11) 23.42 (-2.88)  Ã  Ã  Ã  Ã 

GULP09350 1.85 1.84 (-0.01) 1.85 (0.00) 1.79 (-0.06) 1.81 (-0.04)  Ã  Ã  Ã  Ã 

SELZ11200 3.05 3.03 (-0.02) 2.93 (-0.12) 2.92 (-0.13) 2.46 (-0.59)  Ã  Ã  Ã  Ã  EJJS08400 3.08 3.07 (-0.01) 3.01 (-0.07) 2.91 (-0.17) 2.34 (-0.74)  Ã  Ã  Ã  Ã 

GRB00005 4.80 4.78 (-0.03) 4.49 (-0.31) 4.35 (-0.46) 4.16 (-0.65)  Ã  Ã  Ã  Ã 

GRC00005 0.82 0.82 (0.00) 0.72 (-0.10) 0.69 (-0.14) 0.62 (-0.20)  Ã  Ã  Ã  Ã 

GRD00005 0.00 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) 0.00 (0.00)  Ã  Ã  Ã  Ã 

HEMER10 8.12 8.04 (-0.08) 7.56 (-0.56) 7.37 (-0.75) 7.00 (-1.12)  Ã  Ã  Ã  Ã  ONMO3B 0.00 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) 0.00 (0.00)  Ã  Ã  Ã  Ã 

OMFM7 5.14 5.12 (-0.02) 5.13 (-0.01) 5.10 (-0.03) 5.11 (-0.03)  Ã  Ã  Ã  Ã 

Hydrodynamic study 98 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Table 7.6 Maximum discharges and water levels at some points in the studied catchment for the 5 scenarios for the period 93b, 25/09/1993 10h00 to 28/09/1993 20h00. Between brackets the difference with the reference situation /DEHO VFHQÃ VFHQÃ VFHQÃ VFHQÃ VFHQÃ

P275 12.33 12.29 (-0.04) 11.74 (-0.58) 11.53 (-0.80) 11.79 (-0.54)  Ã  Ã  Ã  Ã 

GEUL02800 15.00 14.91 (-0.09) 14.28 (-0.72) 14.11 (-0.89) 14.39 (-0.61)  Ã  Ã  Ã  Ã 

GEUL03550 16.19 16.10 (-0.09) 15.34 (-0.85) 15.25 (-0.94) 15.50 (-0.69)  Ã  Ã  Ã  Ã 

GEUL12150 41.72 41.37 (-0.35) 39.03 (-2.69) 38.50 (-3.22) 38.75 (-2.97)  Ã  Ã  Ã  Ã  GEUL16550 43.36 42.96 (-0.41) 40.50 (-2.87) 35.71 (-7.65) 40.19 (-3.17)  Ã  Ã  Ã  Ã 

GEUL26450 48.13 47.69 (-0.44) 45.01 (-3.12) 38.37 (-9.76) 44.63 (-3.50)  Ã  Ã  Ã  Ã 

GEUL31250 33.22 32.92 (-0.30) 31.77 (-1.45) 28.76 (-4.45) 31.47 (-1.75)  Ã  Ã  Ã  Ã  GEUL33605 50.89 49.90 (-1.00) 47.28 (-3.62) 39.95 (-10.95) 46.71 (-4.19)  Ã  Ã  Ã  Ã 

GULP09350 6.28 6.22 (-0.06) 5.77 (-0.52) 6.03 (-0.25) 5.93 (-0.35)  Ã  Ã  Ã  Ã 

SELZ11200 5.55 5.44 (-0.11) 5.26 (-0.29) 5.07 (-0.49) 4.34 (-1.22)  Ã  Ã  Ã  Ã  EJJS08400 8.81 8.79 (-0.02) 8.61 (-0.19) 7.75 (-1.06) 6.48 (-2.33)  Ã  Ã  Ã  Ã 

GRB00005 10.23 10.16 (-0.08) 9.52 (-0.71) 7.81 (-2.42) 9.40 (-0.83)  Ã  Ã  Ã  Ã 

GRC00005 7.19 7.02 (-0.17) 6.18 (-1.01) 3.38 (-3.81) 6.00 (-1.19)  Ã  Ã  Ã  Ã 

GRD00005 2.66 2.61 (-0.05) 2.19 (-0.47) 1.10 (-1.56) 2.11 (-0.55)  Ã  Ã  Ã  Ã 

HEMER10 19.17 18.89 (-0.27) 17.23 (-1.94) 13.47 (-5.70) 17.01 (-2.16)  Ã  Ã  Ã  Ã  ONMO3B 0.06 0.06 (0.00) 0.02 (-0.04) 0.02 (-0.04) 0.03 (-0.03)  Ã  Ã  Ã  Ã 

OMFM7 15.60 15.33 (-0.28) 13.50 (-2.11) 9.40 (-6.21) 13.24 (-2.37)  Ã  Ã  Ã  Ã 

Hydrodynamic study 99 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Table 7.7 Maximum discharges and water levels at some points in the studied catchment for the 5 scenarios for the period 98, 13/09/1998 0h00 to 22/09/1998 9h00. Between brackets the difference with the reference situation. /DEHO VFHQÃ VFHQÃ VFHQÃ VFHQÃ VFHQÃ

P275 16.20 16.11 (-0.09) 13.45 (-2.75) 15.21 (-1.00) 15.20 (-1.01)  Ã  Ã  Ã  Ã 

GEUL02800 18.73 18.58 (-0.15) 15.83 (-2.90) 17.59 (-1.14) 17.55 (-1.18)  Ã  Ã  Ã  Ã 

GEUL03550 20.26 20.12 (-0.15) 17.24 (-3.03) 19.09 (-1.17) 18.97 (-1.29)  Ã  Ã  Ã  Ã 

GEUL12150 40.03 39.68 (-0.35) 35.77 (-4.26) 36.78 (-3.25) 38.24 (-1.79)  Ã  Ã  Ã  Ã 

GEUL16550 41.18 40.73 (-0.44) 36.81 (-4.37) 34.79 (-6.38) 39.26 (-1.92)  Ã  Ã  Ã  Ã 

GEUL26450 41.77 41.33 (-0.43) 37.47 (-4.30) 34.96 (-6.80) 39.83 (-1.94)  Ã  Ã  Ã  Ã 

GEUL31250 30.01 29.77 (-0.23) 27.98 (-2.02) 26.33 (-3.68) 29.16 (-0.85)  Ã  Ã  Ã  Ã 

GEUL33605 42.55 42.10 (-0.44) 38.40 (-4.14) 35.40 (-7.15) 40.75 (-1.80)  Ã  Ã  Ã  Ã 

GULP09350 6.42 6.34 (-0.08) 5.86 (-0.57) 6.11 (-0.32) 5.96 (-0.47)  Ã  Ã  Ã  Ã 

SELZ11200 3.40 3.36 (-0.04) 3.20 (-0.20) 3.11 (-0.29) 2.65 (-0.75)  Ã  Ã  Ã  Ã 

EJJS08400 3.72 3.70 (-0.02) 3.62 (-0.10) 3.03 (-0.69) 2.96 (-0.76)  Ã  Ã  Ã  Ã 

GRB00005 8.48 8.40 (-0.08) 7.51 (-0.96) 6.88 (-1.60) 8.06 (-0.42)  Ã  Ã  Ã  Ã 

GRC00005 4.12 3.99 (-0.14) 2.94 (-1.18) 2.20 (-1.92) 3.60 (-0.52)  Ã  Ã  Ã  Ã 

GRD00005 1.51 1.46 (-0.05) 0.92 (-0.59) 0.55 (-0.96) 1.25 (-0.26)  Ã  Ã  Ã  Ã 

HEMER10 15.45 15.20 (-0.25) 13.02 (-2.42) 11.70 (-3.74) 14.36 (-1.08)  Ã  Ã  Ã  Ã 

ONMO3B 0.36 0.35 (-0.01) 0.14 (-0.22) 0.26 (-0.10) 0.26 (-0.10)  Ã  Ã  Ã  Ã 

OMFM7 11.21 10.89 (-0.32) 8.22 (-2.99) 6.79 (-4.42) 9.75 (-1.47)  Ã  Ã  Ã  Ã 

Hydrodynamic study 100 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Table 7.8 Description of the different labels /DEHO 'HVFULSWLRQ

P275 Geul Wallonia

GEUL02800 Geul upstream Volmolen

GEUL03550 Geul upstream Epermolen

GEUL12150 Geul downstream confluence with Gulp, Ejjserbeek and Selzerbeek

GEUL16550 Geul At first constriction device

GEUL26450 Geul, At second constriction device

GEUL31250 Geul upstream Groote Molen

GEUL33605 Geul near Meerssen

GULP09350 Gulp 1 km upstream mouth

SELZ11200 Selzerbeek 1 km upstream mouth

EJJS08400 Ejjserbeek 1 km upstream mouth

GRB00005 Geulke upstream end

GRC00005 Kleine Geul upstream end

GRD00005 Groene overlaat between Geulke and Kleine Geul

HEMER10 Geulhemer mill water canal

ONMO3B Onderste Molen mill water canal

OMFM7 Oude Molen - Franse Molen mill water canal

Hydrodynamic study 101 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

• Even with the use of greenbelts and constriction devices flooding problems occur locally (like for instance upstream of the mills). The overall behaviour of the river system has however improved. Local problems caused by local restrictions in the watercourse (for instance at mills and bridges) should, however, be solved locally.

30

scenario 1 scenario 2 25 scenario 3 scenario 4 scenario 5 20

V  P Ã H UJ 15 D K F LV G 10

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0 260 270 280 290 300 310 320 330 340 WLPHÃ KRXUV

Figure 7.3 Hydrograph in Geul river near Meerssen for five scenarios, for the period 93a

 &RQFOXVLRQVDQGUHFRPPHQGDWLRQV This chapter showed how a one-dimensional hydrodynamic software package like ISIS Flow can be used to evaluate the influence of several flood reducing measures, in the catchment itself as well as changes in the water body, on the discharges and water levels, and consequently on the flooding depths, for different locations in the watercourse. As an example five different scenarios were evaluated. These scenarios contained a hydrological part and a hydrodynamic part. The hydrological part of the scenarios, which mainly focussed on the aspects of land use, was taken into account by changing the inflow of water fluxes in the ISIS model according to the hydrological calculations

Hydrodynamic study 102 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

(Chapter 6). The hydrodynamic part was modelled by changing the hydrodynamic model set-up.

60

scenario 1 scenario 2 50 scenario 3 scenario 4 scenario 5 40

V  P Ã H UJ 30 D K F LV G 20

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0 6410 6420 6430 6440 6450 6460 6470 6480 6490 6500 6510 WLPHÃ KRXUV

Figure 7.4 Hydrograph in Geul near Meerssen for the five scenarios, for the period 93b

The timing and location of the discharge (m³/sec) and the level (m) of the water flowing through the Geul river and its tributaries were simulated as a function of the water inflow calculated in the hydrological study of Chapter 6. This water inflow was calculated for five different scenarios reflecting different land use measures applied in the uplands of the catchment area. Consequently, the discharge and the level of the water flowing through the river canals varied as a function of the different land use scenarios. The land use options aimed to retain water in the uplands and to reduce the (peaks) of water inflow into the river network. Hydraulic infrastructure devices were installed in the river canal in two of the five scenarios. These aimed to retain water in the upstream parts of the river. The maximum water level (m), simulated per scenario, is plotted on a longitudinal profile of the Geul river relative to the height of the riverbanks. Analysis of the profile allowed concluding on where the flood-prone areas are located and which scenario is most favourable to reduce the risk of flash flood events.

Hydrodynamic study 103 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Scenario 1 and 5 reflect the current- and historical discharges (taking into account modifications of land use, but neglecting modifications of the river bed). They differ by 4 to 7% (as obtained in the hydrological study). Simulated water heights differ, on average, by 10 cm (maximally 22 cm) and exceed the height of the riverbanks for both situations.

45

40 scenario 1 scenario 2 35 scenario 3 scenario 4 30 scenario 5 V  P Ã 25 H UJ D K F 20 LV G 15

10

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Figure 7.5 Hydrograph in Geul near Meerssen for the five scenarios, for the period 98

Scenario 2 hardly reduces the risk and effects of flash flood events. Covering the steepest slopes with grassland does not ameliorate the risk of flooding compared to the current reference risk. This is also true when the floodplain roughness is increased by installing bushes in the floodplains as a hydraulic device. Scenario 3 implies all steepest slopes to be afforested. This reduces the risk of flooding close to the historical land use reference risk. Land-related measures of scenario 4 imply the re-introduction of green belts or hedgerows in cultivated farmland, and lead to the same results as scenario 3. The construction of constriction devices (e.g. orifices and pipes) to create retention basins in the upstream parts of the river system significantly affects and reduces the risk of flash flood events. The large peaks in water discharge are attenuated and delayed downstream of these hydraulic constructions.

Hydrodynamic study 104 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Scenario 4 cannot guarantee the complete prevention of flooding. Local flooding zones are identified by means of the calculations; notably near mills along the river. These flooding problems have to be solved locally.

Finally, land use related measures do not significantly reduce the peaks in river water height below the height of the riverbanks. The risk of flooding is therefore not significantly reduced. A reason is that the proposed land-related measures affect only part of the cultivated farming land. If the involved acreage was bigger, for instance grass or afforestation on slopes steeper than 6 or 8%, the effect of the land use transformation would be higher.3 Anyway, the transformation of cultivated steep slopes into pastureland or forest could have a positive effect on local bottlenecks. The creation of upstream water basins by introducing constriction devices in the river canal, combined with land-related measures, does significantly ameliorate the situation. The peaks in river water discharge are reduced and the maximum river water heights are generally below the riverbanks, contrary to all other scenarios. (see Annexe G)

3 This is perhaps shown in scenario 4, where already half of the farming land was transformed in grassland (‘introduction of green belts’), with a resulting larger runoff reduction.

Hydrodynamic study 105 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

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 ,QWURGXFWLRQ Whenever a particular measure is considered to be effective, appropriate instruments, such as laws or regulations, are required to implement the measure. This chapter summarizes the legal instruments, or the framework, for implementing measures within environmental and water management policy and legislation. The objective was to analyse the compatibility and conflicts between recommended flash floods reducing measures and the current legal framework. This analysis could be the starting point for implementing these measures. An inventory of legal instruments was made for both Belgium and the Netherlands on a national, or regional, provincial and local level. As the Belgian part of the Geul catchment basin is located in both the Walloon Region and in a small part of the Flemish Region, a distinction was made between these two regions. Attention had to be paid to the differences between the Dutch, Walloon and Flemish legal framework because these differences are the basis for different approaches in dealing with the current flooding problems. In this chapter, the legal framework and policy instruments are presented for the Netherlands, the Flemish region and the Walloon region. The studies for the three regions are discussed separately. Each time the inventory is compared against some possible flash floods reducing measures as proposed for during the scenario-developing phase in this pilot study. This comparison is presented in an applicability matrix in order to gain an easier insight in the possibility of, or problems concerning, measure implementation. A brief comparison between these applicability matrices is made in the conclusions.

At this stage, in view of the pilot character of the study, the considered measures are not assessed on their territorial applicability in the Geul catchment basin. They are not considered on a plan-level; only the legal applicability is taken into account. However, to implement in practice a measure or a set of measures, a ‘full’ assessment must take place. Both the legal, technical and territorial applicability must be considered, as well as the social acceptance and the costs involved. The measures must be balanced with respect to the specific territorial characteristics of the catchment area. For a successful implementation it is of crucial importance that all involved parties, especially the land users themselves, are convinced of the impact and use of a particular measure. For instance, some of the measures can only be implemented on a voluntary basis. In accordance with the current project, the ecologically sound and sustainable character of a chosen measure must - of course - be obvious.

Legal Framework 106 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

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8.2.1 Actors in the Dutch institutional legal framework The following institutions and organizations are responsible for handling flooding and erosion problems in the Dutch part of the Geul river catchment: • The Province of Limburg • The Waterboard “Roer & Overmaas” • Municipalities • The agricultural sector • Land Development Commissions

The Province of Limburg defines and supervises the tasks of the Waterboard, the municipalities, and the Land Development Commissions. The policy of the Province of Limburg aims at reducing the flooding problems to an acceptable level by introducing structural measures. Measures concerning nature development, land cultivation and infrastructure measures need to be combined and attuned. Provincial policy has a strategic character. The province draws up a strategic framework and the main general lines of policy. Other policy levels should implement the elaboration and realisation of appropriate measures. One of the most important authorities with respect to water management is the Waterboard “Roer en Overmaas”, which is responsible for the operational policy and management regarding flood protection and water quantity in the South and Middle of Limburg. The water management at municipal level (the local public works department) is limited to managing sewerage systems. A municipality also has an important task with respect to land use planning; they are responsible for the land use planning between the municipal borders. The agricultural sector consists of all agricultural institutions and (private) organisations. The local farmers are important stakeholders in water and erosion problems. The LLTB (Limburgse Land en Tuinbouw Bond), which is an agricultural union, is responsible for maintaining relevant agricultural regulations. Land Development Commissions represent public and other interested organisations in regional land development projects. These land development projects aim at improving conditions for agricultural production, at the protection and development of landscape and nature, and at the set-up of recreational facilities. There are three land development projects and three corresponding Land Development Commissions in Southern Limburg: (1) Mergelland, (2) Mergelland Oost, and (3) Centraal Plateau. Annexe F.2 gives a more detailed description of the Dutch institutional framework with respect to the current problems in the Geul catchment.

Legal Framework 107 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

8.2.2 Instruments The considered policy levels each have their own legal and political instruments to deal with flooding and erosion problems (Table 8.1). As for the Dutch part of the catchment, the inventory has been made on a (1) national, (2) provincial and (3) local level. Annexe F gives a more detailed description of each instrument.

Table 8.1 Inventory of the relevant Dutch legal instruments

1DWLRQDOOHYHO 'HFODUDWLRQRI$UOHV This is a joint declaration among the French, German, Belgium, Luxembourg and Dutch Ministers of Environment in which they state the need to reduce flood-related risks as rapidly as possible by focusing on water retention in the Meuse River catchment.

µ$0Y%H[DUWLNHO:HWERGHPEHVFKHUPLQJ¶RUDQRUGLQDQFHIROORZLQJWKH6RLO3URWHFWLRQ$FW The Dutch Soil Protection Act could provide a basis for an AMvB4 (an implementing regulation or ordinance) that aims at reducing erosion problems. The AMvB is a national instrument to be established by the minister himself.

)RUHVWU\3ROLF\3ODQ The Forestry Policy Plan outlines the national forestry policy. It sets the framework for the provincial (regional planning) and municipal policies (zoning plan).

µ/DQGERXZVFKDSVYHURUGHQLQJ¶DV(URVLRQ5HJXODWLRQ The /DQGERXZVFKDSVYHURUGHQLQJ of the Dutch Agricultural Board in The Hague (+RRIGSURGXNWVFKDS $NNHUERXZ) is applicable to erosion-sensitive farming land in Southern Limburg. It contains certain regulations for the cultivation of the most erosion-sensitive grounds.

3URYLQFLDOOHYHO µ6WUHHNSODQ¶RU5HJLRQDOSODQQLQJ 5 The Province of Limburg defines its policy with regard to land use planning in the 6WUHHNSODQ. It translates the national policy into regional policy and it sets the framework for local authorities.

µ3URYLQFLDOH:DWHUKXLVKRXGLQJVSODQ¶RU3URYLQFLDO:DWHU0DQDJHPHQW3ODQ This plan outlines the provincial policy, the functions of the water systems, the desirable developments, functioning and protection of the systems.

3URYLQFLDO5HJXODWLRQ Based on the Environmental Protection Act and the Water Management Act, the Province of Limburg has the possibility to introduce new regulations to deal with the considered flooding and erosion problems. Until now the province did not use this possibility. It has been satisfied with the erosion regulation introduced by the agricultural sector itself.

$JULFXOWXUDO0DQDJHPHQW$JUHHPHQWV The ‘agricultural management agreements’ in the Dutch Agricultural Law aim at government imposed

4 AMvB is the abbreviation for ‘$OJHPHQH0DDWUHJHOYDQ%HVWXXU’. 5 Land use planning, in Dutch known as ‘5XLPWHOLMNH2UGHQLQJ’.

Legal Framework 108 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas management and land use planning which allow agricultural development and conservation of scarce natural areas to co-exist.The province determines which areas are to be assessed as management areas, as nature development areas or as nature reserves.

/RFDOOHYHO :DWHU0DQDJHPHQW3ODQ The Waterboard Roer and Overmaas and the =XLYHULQJVFKDS Limburg (Purification Board) give their vision on water quantity and quality in the Water Management Plan. The plan serves as a guideline for the Waterboard’s water-resources management.

7KHµ.HXU¶RU:DWHUERDUG2UGLQDQFH One of the most important competences of the Waterboard is the possibility to issue byelaws that are necessary for the management of their assignments. By this they can force a third party to act in the preferred way. The Waterboard Ordinance or so-called “Keur” aims at the protection of water works and riverbeds by regulating third parties.

=RQLQJSODQ Each municipality gives its view on the local land use planning through a zoning plan. The plan is a framework for the examination of the potential and current land use.

/DQG'HYHORSPHQW3ODQ Land development projects aim at improving the conditions for agricultural production and the protection and enhancement of the landscape, nature and recreational facilities. For each project, a commission, representing members of public and regional institutions or actors, establishes a land development plan. The projects are sponsored at national policy level.

0DQDJHPHQW$JUHHPHQWVIRUVPDOOVFDOHODQGVFDSHHOHPHQWV Landowners have the opportunity to make an agreement with the Dutch government concerning the maintenance of small-scale landscape elements on their farmland (e.g. green belts, wood). The provincial Council IKL (‘6WLFKWLQJ,QVWDQGKRXGLQJ.OHLQH/DQGVFKDSVHOHPHQWHQ’) is responsible for the execution of this regulation.

Another important development in the considered region is the establishment of a “Declaration of Intent”. The Province of Limburg, the Waterboard, the municipalities of Southern Limburg, the LTTB and the three Land Development Commissions recently undersigned a declaration of intent which aims at strengthening the approach in dealing with erosion and water problems, e.g. the institutions have to be empowered to be able to enforce local regulations. The Declaration will be embodied in a covenant and in an implementation programme.

8.2.3 The applicability matrix The applicability matrix (Table 8.2) compares the instruments as mentioned in part 8.2.2 against several potential flash floods reducing measures (potentially applicable technical measures, simulated in Chapter 6 and 7). The matrix gives an idea about the relevance and the applicability of each instrument with respect to water retention purposes.

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A distinction was made between instruments which are: () applicable (already enforced – symbol used in the applicability matrix is ‘’), () possibly applicable (needs further investigation and elaboration – symbol used in the matrix is ‘’), () not applicable (can not be used in this framework – QRV\PERO in the applicability matrix), () instruments which are not meant for water retention purposes at first, but which could have an indirect positive effect on flash floods reduction while being used for another purpose (symbol in the matrix is ‘L’) and () instruments which are available for protection purposes (the instrument can contribute to the prevention of flooding problems – symbol used in the matrix is ‘S’). The matrix also indicates the time frame over which instruments could be used to implement a measure; a distinction was made between short term (0-5 years), middle long term (5-10 years) and long term (10-15 years). The availability of financial resources and whether usage of the instruments is based on a voluntary basis are also indicated. The outcome of the applicability matrix will be discussed in the next paragraphs.

8.2.3.1 National level The Declaration of Arles, the land use planning policy (Regional Planning), and the Provincial Water Management Plan can be used as sensitisation instruments in the flash floods issues. These instruments are highly valued since recognition of flooding problems on both international and local policy levels is a prerequisite in handling them. The other two instruments at national level, the ‘AMvB’ and the Forestry Plan, are less applicable to water retention purposes. An AMvB, in this case based on the Soil Protection Act, is a very powerful instrument and is not commonly used to reduce ORFDO problems. However, if such an instrument is applied, land use regulations aimed at soil protection and the reduction of erosion problems may be promulgated. The ‘/DQGERXZVFKDSVYHURUGHQLQJ’ of the Dutch Agricultural Board is a land use regulation already being applied to protect farmland against erosion. The policy is formulated at national level and forms the framework for measures at local level. The applicability of this regulation depends on the slope, or gradient, of the farmland. The regulations vary from imposed agricultural techniques in the autumn, for instance the introduction of ground cover, and adjustment of parcels, to the recommendation to turn high sloping parcels into grassland or wood. Such sustainable measures can have a major impact in dealing with the current erosion problems. Thus, the ‘/DQGERXZVFKDSVYHURUGHQLQJ’ is not primarily aimed at water retention; but water retention may well result from these land use regulations. The same applies to the national Forestry Plan. The plan is applicable to water retention purposes on an ad hoc basis. Water retention can be considered as a spin-off of forestry management, whereas water retention is not the main objective of, or reason for these plans.

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Table 8.2 Applicability matrix of Dutch policy instruments versus technical measures Zoning plan Zoning Erosion regulation Erosion Regional Planning Regional Declaration of Arles Declaration Forestry Policy Plan Policy Forestry Provincial regulation Provincial Land Development Plan Land Development Waterboard Regulations Waterboard Water Management Plan Management Water AMvB Soil Protection Act. Protection AMvB Soil Provincial Water Management Plan Management Water Provincial Agricultural Management Agreements Management Agricultural

0HDVXUHV,QVWUXPHQWV elements landscape of management for Agreements Policy of sensitisation and awareness- raising + + + + Incentives policy + i i Adjustment of riverbed 0 + p + + (Re-)allocation of the riverbed 0 + p + + Creation of wetlands 0 + i p + + Ground cover and limited fallow 0 + 0 0 Turn high sloping areas to grassland/wood 0 i + + i p Re-introduction of hedgerows/green belts 0 0 + i i p + + Principles of sustainable farming 0 + Land retirement i 0 p Adjustment of parcelling 0 + + 0 Storage basin (river/upstream) 0 + p + +

3HULRG (l=long; s=short; m=middle long term) s l m s m m s m/l s s s/m m s

)LQDQFLDOUHVRXUFHV (y=yes; n=no) ynynyynyyyyyy 9ROXQWDU\ (y=yes; n=no) nnnnnnnnyynnn

8.2.3.2 Provincial level The Regional Planning and the Provincial Water Management Plan are more or less strategic instruments. They mainly outline the current functions of the area (recreation

Legal Framework 111 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas area, nature reserve etc.), the desirable function development and the functioning and protection of the water systems. As mentioned before, it is quite essential to recognise the current flooding problems during the formulation phase of these plans. Already these instruments play an important role with respect to policy aimed at sensitisation. The Province could issue its own flash floods reducing regulations. From an uni- directional environmental point of view this would not satisfy the current needs, because the Environmental Protection Act has no real basis for agricultural or land use regulations aimed at water retention. From a water managerial point of view, the flooding can be dealt with by the Water Management Act. However, such provincial regulations would not be very practical since the Waterboard already is authorized to introduce this kind of regulations based on its ‘.HXU’. Although the agricultural management agreements are not primarily aimed at water retention purposes, they will contribute indirectly to this objective (i.e., with financial support) for turning high sloping areas into forests and the creation of wetlands.

8.2.3.3 Local level The Water Management Plan of the water manager, Roer and Overmaas, and the Purification Board of Limburg is, or could be, the basis for concrete action in the Geul catchment; for instance in case of adjustment and (re-)allocation of the riverbed, creation of wetlands, introduction of hedgerows or green belts and the construction of storage basins. The time schedule for the introduction of these measures depends on several factors, such as the availability of financial resources and free land. The ‘.HXU’ of the Waterboard plays an important role in the protection of the water works and riverbeds, for it allows the Waterboard to put third parties under the obligation of sustainable water- resources management. A zoning plan can play an important role with regard to the protection against flooding and water erosion by encouraging the introduction of small-scale landscape elements, limiting the paved surface area, prohibiting the conversion of grassland into farming land without licence, and allocating and protecting green belts, water ways and storage basins. The Land Development Plan is a promising instrument. It already is and could be the basis for several measures aimed at water retention purposes. Unfortunately, the instrument also has some disadvantages: (1) it is time-consuming, (2) it is inflexible and (3) the financial resources on national level are limited. The Management Agreements for landscape elements can be applied to the maintenance of landscape elements such as hedgerows and green belts.

8.2.4 Conclusions on the Dutch legal framework The considered actors have several policy instruments at their disposal that already play, or could play, an important role in dealing with current flooding problems. The instruments are multilateral and have been found in many policy sectors (environmental

Legal Framework 112 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas planning, land use management, agriculture…). An important conclusion is that involvement and initiative of DOO these sectors is decisive. As one could see in the applicability matrix, no major conflicts have been found between the available instruments and the potential measures. Each measure can be supported or initiated by at least one instrument. Unfortunately, most of the current instruments are not aimed at reducing flooding and erosion problems. Nevertheless, they often have or could have an indirect positive effect. For instance the Erosion Regulation is a typical example of such an instrument. Limitations of the instruments are also due to factors such as limited financial resources and limited possibilities to claim land. The water management plans and the ‘.HXU’ regulation, both of the Waterboard Roer en Overmaas, the land development plans of the Land Development Commissions, the zoning plan of the several municipalities, and the Erosion Regulation of the Agricultural Board, currently offer the best opportunities to deal with the flooding problems. There still is some uncertainty about the applicability of several instruments. For instance the Erosion Regulation, of which the applicability does not only depend on the legal possibilities, but also on the willingness of the authority or institute in charge. Cooperation is often required for the implementation of an instrument, but also for further investigation of the potency of the instruments.

8.2.5 Recommendations The responsibility for dealing with the current flooding problems, and the possibility to do so, is wide spread among all stakeholders. Cooperation is therefore critical. The recently undersigned “Declaration of Intent” is a good starting point for the new integral approach. The participants have committed themselves to taking concrete action against flooding in the Geul river region. The Province of Limburg plays the key part in dealing with the flooding problems. The policy and implementation of instruments is best co-ordinated at this level. It is quite essential that the current policy regarding water retention becomes well applied in all other provincial plans too. This is even more important since the Province has decided to draw up an Environmental Plan. Furthermore, the provincial policy is to be guiding and should be elaborated on local municipal level. It is recommended that the Province evaluates whether this can be actually done. The provincial role in the Land Development process is a good example of the importance of its position in combating the flooding problems. Many measures aimed at reducing the risk on flash floods can and need to be taken by the Land Development Commission. As the implementation of a Land Development project is rather time- consuming, a precise co-ordination of the process is crucial. In addition, the Land Development Commission declared in a covenant to introduce appropriate measures (as mentioned earlier) and to co-operate when accelerated and temporary measures preventing flash floods need to be established. The municipalities will also co-operate by offering the opportunity to adjust the current zoning plans in case a desired measure is to be implemented.

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The Waterboard will have to continue taking operational measures aimed at sound water quantity management, as it has no authority to introduce agricultural or cultivation measures right now. The Waterboard could investigate the potential effect of the so- called ‘.HXU’ with respect to the flash floods prevention. Another option is to look for possibilities to incorporate an additional regulation aimed at water retention in the current Erosion Regulation. This possibility depends on the willingness of the agricultural sector to co-operate. In the worst case, the Province of Limburg needs to define its own regulation, specifically aimed at water retention and the prevention of flash floods in the region. By the end of 1999, the effectiveness of the Erosion Regulation will be evaluated. In case the results fall below expectations, it would be wise to reconsider this form of regulation and the current fleshing out system. Anyhow, close cooperation with the LTTB (the agricultural union) is crucial for the maintenance of the Erosion Regulation. Furthermore, the Waterboard should play a central part in propagating a progressive vision; with among other things a focus on water retention in all Land Development projects.

 %HOJLXP Belgium is a federal state that consists of communities and regions. The decision- making power in Belgium is no longer exclusively in the hands of the Federal Government and the Federal Parliament. The management of the country falls to several partners, which exercise their competences independently in different fields. The redistribution of power followed two broad lines. The first concerns linguistics and, more broadly, everything relating to culture. It gave rise to the Communities, a concept which refers to the persons that make them up and to the bound that unites them, in this case language and culture. Belgium has three Communities today, based on language: the Flemish Community, the French Community and the German-speaking Community. These correspond to population groups. The second main line of the State reform is historically inspired by economic concerns, expressed by regions which claimed more autonomous power. This gave rise to the founding of three regions: the Flemish Region, the Brussels Capital Region and the Walloon Region. In this Geul project we do not consider the %HOJLDQ legal framework, as the federal state Belgium does not retain any important competence concerning the reduction of the flooding risk in the Geul catchment. The federal state Belgium empowered the Regions to implement the environmental policy (for instance the environmental planning, protection of the environment, water-resources management, land use planning, environmental and agricultural aspects of the European agricultural policy).

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 7KH)OHPLVK5HJLRQ A small part of the Geul catchment is located in the Dutch-speaking part of Belgium. We point at the river Gulp, a tributary of the Geul, which flows for about 5.1 km through Voeren, a small part of the Flemish Province of Limburg. The Flemish Gulp is a natural meandering river with five tributaries worth mentioning: the Bachbeek, the Teuvenbeek, the Sinnichbeek, the Remersdaalbeek and the Mabroekbeek on the Flemish-Walloon border.

8.4.1 Actors in the Flemish institutional legal framework

8.4.1.1 Regional level All administrative services of the Flemish Region and the Flemish Community are concentrated in one ministry, the Ministry of Flanders. The Ministry consists of several Departments, each divided up in Administrations, which, at their turn, consist of Divisions. For this project we are mainly interested in the policy of one department: the Environmental and Infrastructure Department (LIN)6. Most environmental competences in Flanders are embodied in this LIN Department. We will focus on two LIN Administrations, namely AMINAL7 and AROHM8, each divided up in several Divisions (e.g. AMINAL Water, AMINAL Land, AROHM Land Use planning). At this point we can already mention the administrative distinction between the Flemish environmental competences and the competences concerning land use, or ‘town and country’, planning. This distinction can handicap the implementation of solutions to such problems as the Geul flash floods. The Flemish Region also allotted some institutions, societies and companies - which are not really part of, but depending on the Ministry - with specified environmental competences. We mention the VLM9 with, among other things, competences regarding the management of the Flemish manure surplus (the manure bank or ‘0HVWEDQN’) and re-allotment or land consolidation affairs. Besides the LIN another Department of the Ministry of Flanders also holds important stakeholders: the EWBL10 Department, or the department entailing Economy, Employment, Internal Affairs and Agriculture. The Division ‘Municipalities and Provinces’ of the EWBL Administration ‘Internal Affairs’ is responsible for subsidising public works performed by local governments (e.g. sewerage works). The Administration ‘Agriculture and Horticulture’ pursues the Flemish agricultural policy, which for instance influences

6 LIN is the official abbreviation for 'Leefmilieu en Infrastructuur', or Environmental and Infrastructure Department. 7 AMINAL is the official abbreviaton for 'Administratie Milieu-, Natuur-, Land- en Waterbeheer', or the Administration for Environmental, Land and Water-resources Management. 8 AROHM is the official abbreviation for 'Administratie Ruimtelijke Ordening, Huisvesting en Monumenten en Landschappen' and is among others involved in land use planning affairs. 9 VLM is the official abbreviation for ‘Vlaamse Landmaatschappij’, or a companysociety handling for all land affairs concerning land and land use in Flanders. 10 EWBL is the abbreviation for ‘Economie, Werkgelegenheid, Binnenlandse Aangelegenheden en Land- en Tuinbouw’.

Legal Framework 115 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas the manure issues. This Administration is also responsible for subsidising agricultural land use aimed at erosion-reduction.

8.4.1.2 Provincial level There are no environmental competences specific to the provinces. However, the Flemish environmental legislation does charge the provinces with many administrative tasks, mainly concerning the permit-granting procedure. What’s more, the Provincial Council can show autonomous legislative power in issuing byelaws (‘SROLWLHYHURUGHQLQJHQ’) concerning public health, security and order. A double restriction is yet imposed on this legislative power: - The Province can act constitutively if a municipality is unable to ensure the decent settling of a local problem. - The Province has statutory powers LI DQG RQO\ LI the subject cannot be settled decently by federal or regional regulations.

The Watercourses and Territory Section of the Infrastructure Division and the Environment and Nature Division, both part of the Third Directorate of the Flemish Province of Limburg, are the most important actors at this level. The Watercourses Section is the executive office concerning unnavigable watercourses, and actively involved in the design of municipal water-management, or water-control, works. The water-resources policy of the Province of Limburg does focus on: 1. flooding prevention 2. discouraging all accelerated surface water runoff The Provincial authorities specifically emphasise the prevention and reduction of surface runoff on the slopes in the Gulp catchment. According to our informants of the Watercourses Section, the Gulp and Geul flooding problems are especially caused by the natural relief, which points the flooding problems to the Agricultural Section as well.

8.4.1.3 Local level As stakeholders at local level we mention the farmers themselves, the µ%RHUHQERQG¶, an agricultural union, and the city of Voeren with an Agricultural and Environmental Board. Flemish municipalities have a triple environmental competence: - As for the provinces, the federal and regional environmental legislation does charge the municipalities with many tasks, for instance concerning the environmental permit- granting procedure, concerning land use planning (the so-called ‘SODQQHQ YDQ DDQOHJ’) etc.

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- Municipalities can act constitutively by issuing byelaws concerning public health, security and order. These municipal statutory powers can only be used in matters that have not been consigned by law or decree to a higher level of government (province, region, state). - The Chief of Police is an officer of the ‘judicial police’ as well. Therefore he is authorised to trace and record all offences against the environmental legislation. Municipal policemen have booking authority.

In the following part we will give an overview of the relevant Flemish regulations concerning flash floods prevention and restriction. The policy domains of interest are the water-resources management, the environmental policy, the policy concerning land use planning and the agricultural policy. The instruments will be briefly described in part 8.4.2 before being validated in the next part.

8.4.2 Instruments

8.4.2.1 Water-resources management

1. Declaration of Arles (cf. part 8.2.2 in the Dutch legal framework)

2. Basic law concerning the unnavigable watercourses: ‘:HWEHWUHIIHQGHGHRQEHYDDUEDUH ZDWHUORSHQ¶ 3. Basis for police regulations concerning unnavigable watercourses: ‘.RQLQNOLMN%HVOXLWYDQ DXJXVWXV  %6   KRXGHQGH DOJHPHHQ SROLWLHUHJOHPHQW RS GH RQEHYDDUEDUH ZDWHUORSHQ’ 4. Provincial regulation concerning the unnavigable watercourses

5. Provincial subsidy scheme: ‘3URYLQFLDDOVXEVLGLsULQJVEHVOXLW’ 6. Decree with regard to dikes and dams: ‘'HFUHHWYDQDSULO %6 EHWUHIIHQGHGH ZDWHUNHULQJHQ’ and implementing orders 7. Principles of good practice regarding the Flemish sewerage system: ‘.UDFKWOLMQHQ YRRU HHQ JHwQWHJUHHUGULROHULQJVEHOHLGLQ9ODDQGHUHQ  ’ 8. Preliminary decree ‘Integral Water-resources Management’: ‘9RRURQWZHUS YDQ GHFUHHW WRW DDQYXOOLQJYDQKHWGHFUHHWYDQDSULOKRXGHQGHDOJHPHQHEHSDOLQJHQLQ]DNH PLOLHXEHOHLG PHW WLWHOV EHWUHIIHQGH KHW LQWHJUDDO ZDWHUEHKHHU RSSHUYODNWHZDWHUNZDOLWHLW RSSHUYODNWHZDWHUNZDQWLWHLWJURQGZDWHUHQZDWHUYRRU]LHQLQJ  ’ 9. Water management plans: ‘ZDWHUKXLVKRXGLQJVSODQQHQ’

For the Flemish Region, the basic law of 1967 has been supplemented with the Decree of 1983 regarding the clearing of unnavigable watercourses.11 Among other things, the law identifies three categories of unnavigable watercourses and assigns the managers of each category.

11 ‘Decreet van 21.04.83 houdende de ruiming van onbevaarbare waterlopen.’

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The Gulp river and the Mabroekbeek are classified watercourses of second category; the Bachbeek, the Teuvenbeek, the Sinnichbeek and the Remersdaalbeek are classified as third category. The Gulp river and its tributaries do not belong to a territory managed by a ‘Polder’ or ‘Wateringen’ Board. Clearing, maintenance and restoration works on unnavigable watercourses of second category are performed by the provincial government. Municipalities are responsible for the management of unnavigable watercourses of third category. All activities on watercourses of second and third category have to be performed according to the ‘Provincial regulation concerning the unnavigable watercourses’. Provincial officials have police competence on the unnavigable watercourses of second and third category, and on the non-classified unnavigable watercourses.

Some extra-ordinary water management activities12 need a construction licence, and some need a MER13, an environmental impact assessment, as well (regional competence – fitting in with the legislation on Land Use Planning). The requirement of a construction licence or a MER depends, among other things, on the water-management works taking place in particular ‘zones’ of the Flemish ‘JHZHVWSODQ’,or regional plan (for instance areas identified as nature area or reserve, area of important ecological value…). As for a storage basin, a MER is required from a surface area of 50 ha on. Provincial authorisation is required for the execution of all extra-ordinary improvement or/and adjustment works on unnavigable watercourses of second and third category. This authorisation has to be granted by the ‘%HVWHQGLJH 'HSXWDWLH’, the Permanent Deputation, of the Province of Limburg (provincial competence).

The Province subsidises all local water-management works up to 20% of the total cost. According to the ‘Provincial subsidy scheme’ expropriation of privately owned land, which is necessary for the construction of a storage basin, can also be subsidised. Such a storage basin does not need to be on the watercourse itself: an upstream basin can be subsidised as well. Even green belts along the watercourse, with enough hydraulic impact on the watercourse and providing additional storage capacity, can be considered for subsidisation. The Province can also purchase the land necessary to restore the natural meandering of a watercourse. Of course, this is not relevant for the Flemish Gulp and its tributaries since these watercourses never have been adjusted.

The decree regarding 'dikes and dams' empowers the Flemish government to expropriate privately owned real property along the watercourse for the sake of the public welfare: e.g. for the construction of dams, for flood control reservoirs, storage basins and access roads. This expropriation competence also applies for the restoration of natural floodplains. As for the unnavigable watercourses this expropriation possibility is restricted to watercourses of first category.

12 as opposed to the ordinary clearing, maintaining and restoration. 13 MER is the official abbreviation for ‘Milieu Effecten Rapportering’, or a report considering all possible environmental impacts of a certain activity (Environmental Impact Assessment – EIA).

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We do mention the sewerage policy, ‘Principles of good practice regarding the Flemish sewerage system’, because of its sensitisation relevance. The principles aim at restricting the precipitation runoff (e.g. maximum disconnection of the paved surface runoff and of the watercourses from the sewerage system; limits to overflow), at maximum infiltration and at retarded surface water drainage via trenches. The sewerage policy especially counts at local level. Of course, there is only little paved surface in the Gulp valley.

A note including main action points (‘NUDFKWOLMQHQQRWD’) lays down the foundation for the realisation of the integral water-resources management in the Flemish Region. A water- policy, fitting in the environmental policy, is drawn up based upon these main action points. On the level of one or more river basins, the integral water-resources policy is being accomplished through a river basin-management plan. The preliminary decree ‘Integral Water-resources Management’ provides for the Flemish government establishing a water-management policy and these river basin-management plans every five years. It also provides for binding planning terms and for the competences regarding the three sub-plans (water-quality, water-quantity and geomorphologic structure). In the Flemish Region, a step forward towards the realisation of integral water-resources management was made by means of this preliminary decree.

AMINAL Water establishes water-management plans, or the policy with regard to water- quantity. It has been assumed that the ‘new’ water-control works should be resulting from balancing all functions and objectives of the water-resources system. This will be based upon the hydrological modelling of the catchment of unnavigable watercourses. All parties, or stakeholders, are involved in the planning phase through a local platform. The plans will not only focus on the water-control works, but also on the possible buffering of water in the valleys and on the reciprocity between water-resources management and land use planning.

For the sake of completeness, all actors relevant to the water quantity management in the Flemish Region are summarised in Table 8.3.

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Table 8.3 Actors relevant to the water quantity management

&RPSRQHQWRIWKH:DWHUUHVRXUFHVV\VWHP 5HVSRQVLEOHPDQDJHUV SURFACEWATER QUANTITY Navigable watercourses AWZ14, with separate divisions for: • The Coast • Upper Scheldt • Sea Scheldt • Meuse and Albertchannel Unnavigable watercourses AMINAL (first category) • The Water Division Unnavigable watercourses Province (second category) Unnavigable watercourses Municipality supervised by the Province (third category) Unnavigable watercourses Adjacent landowners (non-classified) Watercourses located in 'Polders' or Polder or Wateringen Board 'Wateringen'

GROUNDWATER QUANTITY AMINAL • The Water Division • The Permit Division

8.4.2.2 Land use planning 1. Decree concerning the land use planning in the Flemish Region: ‘'HFUHHWKRXGHQGH GHUXLPWHOLMNHRUGHQLQJYDQPDDUW %6 KRXGHQGHGHEHNUDFKWLJLQJ YDQKHW%HVOXLWYDQGH9ODDPVH5HJHULQJYDQRNWREHU %6 ’ The decree introduces the master planning that has to be implemented at the three Flemish policy levels. All three planning levels can provide for implementing ordinances. The Provincial and municipal planning levels can provide for compulsory directives as well. The reader will find an overview in Table 8.4. Municipalities have the possibility to issue so-called ‘building ordinances’, by which they can impose a licence-requirement on certain – in itself licence-free – operations. This can be important in case of interventions endangering small-scale landscape elements (e.g. wood cutting, small relief alteration, vegetation alteration...).

14 AWZ is the official abbreviation for 'Administratie Waterwegen en Zeewezen', or the LIN administration responsible for the navigable waterways and marine management.

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AROHM Land Use planning co-ordinates and directs the actions of the local ROHM divisions15 concerning their support in the land use planning process of the local authorities.

Table 8.4 Land use planning in the Flemish Region

)OHPLVK5HJLRQ 3URYLQFH 0XQLFLSDOLW\ 16 17 18 :KDW RSV Provincial RS local RS :KR Flemish Government Provincial council Municipal council (i.e. AROHM Land Use planning) 19 ,PSOHPHQW *HZHVWSODQQHQ 3ODQQHQYDQ$DQOHJ APA’s (regional planning) (layout planning) DWLRQ BPA’s20 Regional ordinances (setout by the Flemish (amendments of the government) muncipal PA’s by the Flemish government are Provincial ordinances not uncommon) (approbation by the Municipal ordinances Flemish government needed) (approbation by the Flemish government needed)

2. Law of 1962 concerning the organisation of the land use planning: ‘:HWYDQ $UWKRXGHQGHRUJDQLVDWLHYDQGHUXLPWHOLMNHRUGHHQVWHGHERXZ’ This article stipulates that the cutting down or digging up of straight timber (trees measuring one meter around at the foot of the trunk) has to be licensed by the municipality.

3. Land consolidation and land development planning Farmers usually ask for a land consolidation project. They ask for connected parcels, without barriers, in order to increase produce of their lands. First, expert-consultants will inventory all distinct elements in the considered parcels. Besides this inventory they will give their opinion on, and perception of, the value of certain elements (e.g. on green belts, small-scale landscape elements) as well. A MER, an environmental impact assessment, usually has to be performed. The Land Consolidation Committee, together with the VLM and all stakeholders involved, will draw up a landscape plan and a

15 AROHM has a field organization (called ROHM) in all Flemish provinces. 16 This is the outline for the Flemish regional Master Plan and the abbreviaton for ‘5XLPWHOLMN6WUXFWXXUSODQ ’. 179ODDQGHUHQ This is a master plan at provincial level, and RS is the abbreviation for ‘5XLPWHOLMN6WUXFWXXUSODQ’. 18 This is the master plan at the level of the municipality. 19 The ‘ ’, or ordinary layout planning. 20 $OJHPHQH3ODQQHQYDQ$DQOHJ The ‘%LM]RQGHUH3ODQQHQYDQ$DQOHJ’, or extra-ordinary layout planning.

Legal Framework 121 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas reallotment plan with adjusted parcel borders. AMINAL Land has to follow up the land consolidation project. The Province has to refund the Land Consolidation Committee for cleaning, maintenance and restoration works on unnavigable watercourses of second category. The Province advises on, and pays for, extra-ordinary improvement and modification works. The Province also advises on watercourses to be filled in or re-designed during a land consolidation project. Watercourses or ditches dug as part of a land consolidation project do not require a construction licence.

Large connected parcels in a hilly region have some disastrous consequences: they increase soil erosion and accelerate the surface runoff. And this Geul-project precisely aims at avoiding or restricting these two processes… Therefore land consolidation projects always have to be linked to preconditions concerning sustainable land use (e.g. conservation or re-construction of green belts). Unfortunately, these conditions cannot be enforced by this time being. They can only be implemented after giving adequate education. A maximum of 2% of the surface area, which was not used for farming purposes EHIRUH the land consolidation project, can be claimed for land or nature development measures. Our informants of AMINAL Water and the Province of Limburg did mention the urgent need in the Flemish Region to reconsider land consolidation projects at parcel-level and to link these projects with land development planning.

Land development planning usually covers a much wider area than the land consolidation projects. The VLM, together with the Land Development Committee and many stakeholders draw up the Land Development Plan. AMINAL Land follows up this planning phase. Once the Land Development Plan has been approved, the implementation is left to third parties. The VLM has the possibility to subsidise a Land Development Project by means of the ‘Land Development Fund’. Of course, these subsidies can only indirectly be used for runoff reduction. The first land development projects are in progress; it concerns however small-scaled interventions for now.

8.4.2.3 Land use and agricultural policy 1. Principles of sustainable farming: ‘&RGHYRRUJRHGHODQGERXZSUDNWLMNHQ’ The principles of sustainable farming are formulated with – among other things – the intention of combating the erosion problems at first, and are only indirectly aimed at water retention. The farmers are the target group. They are approached directly, but under no obligation to implement the principles. By Order of the Flemish Government (Administration of Agriculture and Horticulture), the application of sustainable methods of agriculture can be subsidised. This Order follows the European Ordinance 2078/92, which discusses the financial support for agricultural methods that are compatible with environmental protection and nature conservation. For instance, contour ploughing and maintaining ground cover during winter season are

Legal Framework 122 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas methods that could be subsidised21. Until recently no education or information sessions were organised for the farmers. Consequently, they distrusted the proposed ‘new style’ methods of agriculture. Municipalities can issue a bye-law (a local ordinance) to enforce (some of) the principles of sustainable farming in the context of erosion restriction or flooding prevention, e.g. the bye-law issued by the city of Aarschot, i.e. ‘*HPHHQWHOLMNSROLWLHUHJOHPHQWEHWUHIIHQGHGH EHYHLOLJLQJWHJHQRYHUVWURPLQJ’.

2. Decree regarding the Flemish manure problem: ‘'HFUHHW YDQ  WRW EHVFKHUPLQJ YDQ KHW OHHIPLOLHX WHJHQ GH YHURQWUHLQLJLQJ GRRU PHVWVWRIIHQ’ and implementing orders Among other things this decree regulates a manuring ban in the 5-meter zone, measured from the watercourse towards the land, along a watercourse.

3. Decree with regard to the protection of landscapes: ‘'HFUHHWYDQRYHUGH EHVFKHUPLQJYDQODQGVFKDSSHQ’, and implementing order of 03.06.97 concerning the cultivation ban of everlasting grasslands. This decree is valid in ‘agrarian regions of considerable natural beauty’.

4. The Forest decree, regulating the organisation and management of the Flemish forests The Forestry division of AMINAL can subsidise the afforestation of farmland (by enforcement of the European Ordinance 2080/92). All owners of farmland can join, provided that their afforestation covers at least 0.5 ha.

8.4.2.4 Environmental policy 1. Environmental policy plan at regional level: ‘0LOLHXEHOHLGVSODQ’ or MINA- plan 2 From 1997 to 2001 this plan is nothing less than the guideline for the Flemish government to define its environmental policy. Each year, the Flemish government draws up an environmental agenda (‘0LOLHXMDDUSURJUDPPD’) in order to implement the MINA-plan 2. This agenda indicates which part of the plan is implemented each year and also contains a financial plan, which is added to the yearly budget-proposal of the government. The MINA-plan 2 contains a ‘plan of action’, dealing with a number of topics (actual environmental problems). Within each topic, specific aims, strategies, actions or initiatives are developed. Some actions are binding and financed; others non-binding and not yet financed. A number of actions from the subjects ‘Dehydration’ and ‘Area- oriented approach’ are relevant for the Geul-project.

21 Europe and the Flemish Region each pay half of the subsidy.

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Amongst others dehydration is caused by a more rapid runoff of surface water, due to the expansion of paved surfaces and due to certain water-control works.

The following actions are worth mentioning: - Action 66: ‘Developing and improving policy instruments regarding land use.’ Land-usage should be geared to the water-resources system’s characteristics through the policy for land use planning. The action includes amongst others the drawing up of charts of floodplains (flooded areas), valley lands and areas where unnavigable waterways can freely meander. The environmental (i.e. spatial) implications of the measures to be taken must fit in with the RSV. - Action 71: ‘Renewal of the legislation on water quantity management.’ The legislation on unnavigable waterways is still based on a narrow, obsolete view of the watercourse. The current ‘basic law of 1967’ is still aimed at faster runoff. This action fits in with the current view on integral water-resources management in the Flemish region and proposes, among other things, a simplification of the current spread of competences among the various policy levels. - Action 72: ‘Stimulating infiltration and local storage and slowing down surface water runoff.’ This is a binding action, proposing measures concerning the slowing down and storage of surface water, by constructing green belts along parcel-borders, roads and waterways and/or by means of storage basins and floodplains. - Action 74: ‘Further development and application of environment-friendly technologies regarding the organisation and management of waterways.’ The existing regulations (‘9DGHPHFXP1DWXXUWHFKQLVFKH0LOLHXERXZ±:DWHUORSHQ’) are supplemented, if necessary adjusted. They are combined as “Main action points for the organisation and management of unnavigable watercourses”, and Provinces, municipalities, Polder Boards and Wateringen Boards must conform to these. Additional funds are provided for. This action, however, is non-binding. Among other things, QDWXUDO floodplains may be used in the implementation phase of this action.

A number of other important actions form part of the topic ‘Area-oriented approach’. - Action 127: ‘Realisation of environmental objectives using lay-out planning (SODQQHQ YDQDDQOHJ).’ This action puts first and foremost the link between environmental management and town and country, or environmental, planning. - Action 129: ‘Establishing a platform for integral water-resources management in the Flemish Region.’ This action is binding. It offers a link between land use planning and integral water- resources management by seeking to convergence of procedures and planning (e.g.

Legal Framework 124 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas land use planning could answer to the need of flooding by applying a construction ban in the valleys with a risk of flooding). - Action 130: ‘Establishing a river basin platform.’ (binding) - Action 131: ‘Drawing up integral river basin-management plans.’ (binding) - Action 133: ‘Making land development a fully-fledged tool.’ (binding) Action 133 implies at least the creation of a fully-fledged legal framework for land development, with a far-reaching set of tools and feasible procedures. The current tool for land development must be made more operational by increasing the feasibility of the procedures and extending the set of tools and (financial) resources.

As a tool, the MINA-plan 2 is most suitable then for the development of a policy plan, which has to be elaborated in a number of actions and initiatives.

2. Environmental policy plan at provincial level: ‘0LOLHXEHOHLGVSODQ/LPEXUJ’ This environmental policy plan implements the regional MINA-plan 2 at the provincial level. It should therefore not contradict the regional environmental policy. The current 0LOLHXEHOHLGVSODQ/LPEXUJ mentions the problem of undesired flash floods in the Limburg region. According to the compilers of the plan, there are two causes lying on the basis of these floods: the rather steep slopes in the basin and the large amount of paved surface with sewers and overflows. Some actions out of the Water section in the environmental policy plan can be applicable in the Geul project: - Action 10: ‘Take flow control (reducing) measures.’ To prevent floods, the Province of Limburg proposes the introduction of storage basins and the definition of natural flood-prone areas. Enlarging waterways (to widen or deepen) is not desirable. Surface runoff is to be opposed to a maximum. - Action 13: ‘Aim for meandering, establish buffer zones along waterways and develop waterway-accompanying ecosystems.’

Some other actions of the section ‘Area-oriented environmental policy’ are relevant as well: - Action 2: ‘Propose green modifications to the regional planning concerning stream valleys.’ By this stream valleys can get the necessary planological protection. The basis for the necessary green modifications to the regional planning already lies in the provincial RS (spatial master plan). - Action 4: ‘Develop a purchase policy for bank strips along waterways.’

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The Province of Limburg draws up its own purchase policy for unnavigable watercourses of second category and buys the bank strips. Problem areas, such as flood-prone areas, come first. Local municipal authorities get an allowance from the Province for the purchase of bank strips along watercourses of third category. - Action 8: ‘Set up a sustainable structure for the preservation and development of small- scale landscape elements (SLE)’ Examples of these SLE, as defined in the ‘nature decree’, are JUDIWHQ, orchards, vegetation on parcel borders, bushes and wood. The Province of Limburg regularly organizes sensitisation-campaigns concerning the preservation of these small-scale landscape elements and there is also a special provincial subsidy regulation for it. - Action 12: ‘Investigate the possibilities for ecologically sensible wood expansion.’ This means, among other things, the afforestation of erosion-sensitive slopes. This ‘slope wood’ is examined in cooperation with AMINAL and the involved municipalities.

3. Environmental policy plan at municipal level Municipalities too can draw up environmental policy plans. These plans must not contradict the provincial and regional environmental policy plan.

4. Decree of 21.10.97 concerning the preservation of nature and the natural environment: ‘'HFUHHWYDQEHWUHIIHQGHKHWQDWXXUEHKRXGHQKHWQDWXXUOLMN PLOLHX’ or the ‘1DWXXUEHKRXGVGHFUHHW’ (nature decree) with first enforcement decree of 23.07.98. The nature decree defines, among other things, small-scale landscape elements (verges, trees, bushes, banks, JUDIWHQ or cultured (man-made) talus, hedges, wood, high-trunk orchards, vegetation on parcel borders...). *UDIWHQ are typical for the region of Voeren. Especially the fourth part of the enforcement decree is of interest. It mentions a license-requirement for modifying certain vegetation-types and for modifying SLE (e.g. a ban on certain modifications; a license-requirement for modifying the vegetation in certain areas or zones of the regional plan, an obligation to report certain modifications (e.g. digging out and straightening of streams)). The license is applied for at, and granted by, the municipal executive of the municipality, or – in some cases – by the Permanent Deputation of the Province.

The Flemish Government can, in the interest of preserving nature, close ‘voluntary management agreements’ with the land users. A management agreement is an agreement with which the land user commits himself voluntarily to deliver a pre- determined performance for a certain period of time. This performance is aimed at accomplishing a higher environmental quality than the basis-environmental quality. This can be done by maintaining or developing certain nature-values, for payment of a pre- determined reimbursement. A performance can also exist in neglecting certain land use activities, such as letting the acre weeds grow in parcel peripherals or borders, instead of removing them.

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Management agreements are closed with the VLM, the Flemish Land Society, and are first of all meant for farmers, among other things with the view to this parcel borders management. The first management agreements between farmers and the Flemish government can come into effect on January 1, 2000. AMINAL and the VLM supervise the management agreements. The management reimbursements are paid half by the European Union, and half by the Flemish Government. Management agreements do fit in with the European agricultural and environmental policy (European ordinances 2078/92 en 1257/99). Provinces and municipalities too can close voluntary management agreements with private persons. These management agreements are mainly focused on linear and ‘point-like’ landscape elements (SLE) and on the presence of nature in the built-up area. For instance municipalities can do so in the framework of a municipal nature development plan (*HPHHQWHOLMN 1DWXXURQWZLNNHOLQJVSODQ or GNOP). A municipality or province can also decide to raise the management remuneration, as paid by Europe and the Flemish Region, with 30% at the most.22.

The nature decree offers several opportunities for nature conservation. Performing nature development projects (QDWXXULQULFKWLQJVSURMHFWHQ) is one of them. It’s a means to plan an area or domain, of a certain land use type, with a view to nature preservation, - restoration or –development. The Flemish Government can introduce a nature development project in a chosen area, take measures and execute the necessary works to implement these measures. The Flemish Region pays all costs for the preparation and execution of such projects. Although aiming at different objectives, the measures offered by nature development projects can be compared with the measures identified in land consolidation projects, improving agri- and horticulture in the considered region. Within the scope of a nature development project, water management works can be performed, such as alterations to the riverbanks, or to the longitudinal- and cross sections of a watercourse (e.g. restoration of meandering), adjustment of water supply and drainage, alteration of the water level etc. These works are aimed at restoring or creating a specific habitat for certain plant and animal species; they are not aimed at flash floods reduction. However, increased water retention, and a decreased risk of flash floods, can be realized as indirect effects.

The Flemish Region and the Flemish municipalities can obtain privately owned parcels of land for reasons of nature preservation by expropriation for the ‘public welfare’.

5. Municipal nature development plan or GNOP A municipality can draw up a nature development plan or GNOP in accordance with the criteria of the ‘Municipal Environmental Covenant 1992-1996’. The municipality of Voeren however did not undersign this Environmental Covenant; neither drew up a nature development plan up till now.

22 Remunerations received on the basis of the European ordinances 2078/92 and 1257/99 may not exceed a certain sum per hectare.

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8.4.3 The applicability matrix The applicability matrix (Table 8.5) compares the inventoried Flemish regulations and instruments against potential flash floods reducing measures. The measures are validated for their water retention purpose at first; so the matrix can give an idea about the relevance and the applicability of each instrument with respect to this water retention. A distinction was made between instruments which are: () applicable (already enforced – symbol used in the applicability matrix is ‘’), () possibly applicable (needs further investigation and elaboration – symbol used in the matrix is ‘’), () not applicable (can not be used in this framework – QR V\PERO in the applicability matrix) for the implementation of the measure aimed at water retention, and () instruments which are not meant for water retention purposes at first, but which have an indirect positive effect on flash floods reduction (symbol in the matrix is ‘L’). The matrix also gives an indication about the time frame over which instruments could be used to implement a measure; a distinction was made between short term (0-5 years), moderate long term (5-10 years) and long term (10-15 years). The availability of financial resources, and the use of instruments on a voluntary basis or not is also indicated.

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Table 8.5 Applicability matrix for the Flemish legal framework

Q) OD

23 WS V H Z H J MINA-plan 2 MINA-plan Nature decree Manure decree Water management plans Forest subsidies decree + Management Agreements Milieubeleidsplan Limburg Principlessustainable of farming Water-resources management Decree regarding dikes and dams Integral water-resources management RSV& Planning Regional ( Principlessewerage system – good practice of Land consolidationland & development planning Provinciallayoutlocal / planning BPA’s and APA’s H VXUHVÃ Ã, VWUXPH WV

Policy of sensitisation & awareness-raising 0 0 + + + 0 0 0 i + + + Incentives policy 0 0 0(i) 0 i i i i Adjustment of riverbed 0 0 + + + (Re-) allocation of the riverbed 0 0 0 + 0 0 + + + + Creation of wetlands 0 + 0 0 + 0 + Ground cover and limited fallow i i 0(i) Turn high sloping cultivated areas to grassland/wood i i +(i) 0 0(i) Reintroduction of hedgerows/green belts 0 0 0/i +(i) i + + + +(i) Principles of sustainable farming i Land retirement 0 0 0 0 i i i 0 + 0 0 0 Adjustment of parcelling i i 0(i) Storage basin (river/upstream) 0000000+ 00+

3HULRG (s=short; m=middle long; l=long term) s s s s/m m m s/m m/l s/m s s m m m s )LQDQFLDOÃUHVRXUFHV (y=yes; n=no) yyyyyyyyynyyyyy 9ROXQWDU\Ã(y=yes; n=no) ynnnnnnnynyn/yn/yny

Until recently the Flemish water-resources management was not quite oriented towards ‘water retention’. For instance, the ordinary maintenance and restoration works in the basic law of ’67 are still meant to secure a fluent water flow. The extra-ordinary modification and improvement works, however, can literally be interpreted as ‘to

23 At this point, the term ‘water-resources management’ covers the basic law of ’67 concerning unnavigable watercourses; the provincial regulation concerning the unnavigable watercourses and the provincial subsidy scheme as mentioned in part 8.4.2.1.

Legal Framework 129 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas improve’ — and so, if necessary, even slow down — the flow. The Province of Limburg therefore describes these improvement works as ‘DUUDQJLQJ WKH ZDWHU IORZ WR SUHYHQW IORRGV’. For instance, the Province considers the development of floodplains and storage basins as such extra-ordinary improvement works, which can be subsidised. However, whether or not slowing down the runoff still happens voluntarily within the framework of this legislation: there is no obligation included in the law of ’67. One can freely choose between locally storing the excess of water or enlarging the watercourse. Fortunately, there is a wind of change blowing through the water-resources policy right now. The preliminary decree on integral water-resources management, and some actions out of the regional environmental policy plan (MINA-plan 2) and out of the environmental policy plan of the Province of Limburg are good examples of the new approach. The reader can see the applicability matrix showing the ‘SRVVLEO\ DSSOLFDEOH’ symbol for the instruments regarding water-resources management; for these instruments could indeed implement a number of measures, but still need some re-orientation and elaboration at first. The MINA-plan 2 and the Limburg environmental policy plan already make a move in the right direction. The ‘principles of good practice regarding the Flemish sewerage system’ are ideally to be used as sensitisation instrument in making all stakeholders aware of the need of an enhanced storage capacity and water retention. The other water management instruments could also be used for this awareness-raising purpose.

The compulsory directives of the 5XLPWHOLMN 6WUXFWXXUSODQ 9ODDQGHUHQ (RSV) can be involved to preserve the available storage capacity in the river basin as far as possible. For instance, building along watercourses, and the granting of the necessary building permits, should be strictly regulated. Another possibility to enhance the available storage capacity is the (re)introduction of small-scale landscape elements (e.g. green belts) by means of these ‘compulsory directives’. The RSV does not yet show any binding stipulations concerning water quantity management in itself. Green belts along the watercourse, and green belts along the contour lines of a cultivated slope, can be realized within land consolidation, land development projects and nature development projects too. Specific stipulations are needed to make sure that for example ‘erosion sensitive locations’ get classified as ‘grass way’. Such classification is at first aimed at erosion reduction; water retention is only considered as an indirect or secondary effect. If a land development plan provides for grassed waterways, the land needed has to be purchased by AMINAL Water or by the Province. Expropriation still happens on a voluntary basis. The introduction of green belts, or hedgerows, by means of the implementation of these instruments will take a considerable amount of time. The applicability matrix shows a moderate long to long time frame. Green belts along a watercourse could also result, as an indirect effect, from the implementation of the building ban following the manure decree. Preservation and reintroduction of other small-scale landscape elements and micro relief can be established within the framework of a ‘new style’ land consolidation project as well. This kind of measures is particularly aimed at erosion combating by, for instance, restricting the length of a slope. The adjusted parcelling will provide for enhanced water retention as an indirect effect.

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Flood plains and flood-prone areas should be defined and demarcated in the regional planning process. Adjustments to the Flemish ‘JHZHVWSODQ’ (regional plan) may be needed. For this, particular areas must be defined where all works and operations are forbidden or subordinate to rigid stipulations as long as the necessary measures to reduce the flooding risk are not taken. The demarcation and development of wetlands can be established by implementing a land development or land consolidation project. In Flanders, small storage basins are also often constructed while implementing a land development or land consolidation project. The construction can be subsidised, and land will be purchased through ‘expropriation for the public welfare’.

8.4.4 Conclusions on the Flemish legal framework While studying the applicability matrix for the Flemish Region, the reader will remark that all inventoried measures can be implemented somehow or other within the current legal framework. However, he will also remark that most of the instruments are not directly meant to implement measures aiming at water retention or flash floods reduction. They are at first designed for other purposes, such as erosion combating or development of ‘nature values’. Limiting of runoff will be a secondary result of implementing measures intended at these goals. The instruments therefore still need some elaboration and reorientation in order to be applicable for water retention purposes.

The appeal of some potentially interesting measures is limited by the fact that they have no general applicability (for instance measures of which the implementation is limited to nature reserves, or limited to the context of land consolidation projects). The general applicability is also important in the context of avoiding certain interventions. For instance there is no licence or authorisation required for harmful interventions such as drainage, ploughing up pastureland, grubbing up hedgerows, paving tracks etc. if these interventions do not take place in areas specifically classified by the Flemish Government (such as moors, nature reserves, areas of valuable landscape…). The spatial focus of a number of existing regulations should be reconsidered.

The Flemish instruments concerning land consolidation, land development and nature development appear to be most powerful regarding the implementation of water retention enhancing measures. Of course, such projects are implemented over a moderate long to long time frame and often still rely on the goodwill of the actors and stakeholders involved. Information and sensitisation on the flooding problem, its possible causes and possible environmentally sound solutions to prevent or reduce the risk of flooding are of paramount importance. Land users must be aware of the impact of interventions in the (upstream parts of the) catchment on the water system in the downstream parts. Sustainable and environmentally sound agricultural practices should be promoted among the farmers; flood-prone areas should be safeguarded against infrastructure by means of a sound land use planning. Effectively using the possibility for including compulsory directives in the Flemish land use planning could contribute to this aim.

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Unfortunately, these directives or orders are often omitted because of their (politically) delicate character (for instance the power of the Agricultural Union regarding expropriations, or the attitude of land users towards the ban on certain cultivation methods). This once more shows the importance of a thorough sensitisation and awareness-raising campaign.

The water management policy of the Province of Limburg is directed towards flooding prevention and restricting or reducing the accelerated surface water runoff. They show a preference for storage reservoirs, floodplains and sediment traps, which can be implemented within the current legal framework as shown in the preceding chapter.

Finally, the Gulp region itself does not experience severe flash floods problems. According to the town clerk of the city of Voeren, the water quality of the Gulp river is a more compelling problem than the water quantity (heavy metal pollution due to former mining activity in the Geul catchment). Therefore nothing structural is being done at present to prevent downstream flooding. Before acting on the discharge, qualitative measurements will be executed first (e.g. the construction of two sewage treatment plants is planned in the region). Problems following flash flood events, problems concerning water quality and the ecological protection of the river are recently integrated within the ‘integrated water management’ policy of the Flemish Government. The water systems in the Flemish Region have high expectations for the implementation of this new instrument!

The decree regarding integral water-resources management, its implementation and execution, cause an important change in the Flemish Region. The environmental policy (nature and water conservation), the policy concerning land use planning, the socio- economical policy and the agricultural policy are being integrated. The competences however remain fragmented, which is not quite beneficial for the global perception. Integral water-resources management causes the water system being managed to comply all of its functions. Support of this integral water-resources management by the land use planning policy includes the need for valleys to remain free from being built-on so that natural flooding remains possible and potential conflicts between housing and water are prevented. The perception of both land use planners and water managers is joined by drawing up integral river basin-management plans (‘EHNNHQEHKHHUVSODQQHQ’) (operational plans at the level of the river catchment basin, strategic plans at a higher level), whereas the planning is carried out at the level of the environmental policy.

8.4.5 Recommendations – Flemish Region Besides the recommendations already formulated among the conclusions of part 8.4.4, two major general remarks can be added: - the water system should be considered and accepted as one of the guiding principles in the land use planning policy;

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- land consolidation projects and land development projects should be considered as regulating and stimulating instruments regarding the planning of the agrarian infrastructure. By introducing the decree concerning integral water-resources management and the bekkenbeheersplannen, the Flemish Government has made a first step towards a sustainable catchment management in Flanders. Many of its aspects however still rely on the goodwill and sensitisation of the stakeholders. Therefore it is absolutely required to spend enough attention on the supply of information and sensitisation. The implementation of the integral water management still needs to be better legally founded. The competences remain fragmented among several administrations, which is not quite beneficial for a global and integral perception.

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8.5.1 Actors in the Walloon institutional legal framework

8.5.1.1 Regional level As is the case in the Flemish region, all administrative services of the Walloon region are concentrated in one ministry, the Ministry of the Walloon Region. This ministry counts nine General Directions. Each general direction is divided in Divisions; the Divisions in Directions. Three General Directions are important in the framework of the present study: the General Direction of Natural Resources and Environment ('LUHFWLRQ *pQpUDOH GHV 5HVVRXUFHV1DWXUHOOHVHWGHO¶(QYLURQQHPHQW or DGRNE), the General Direction of town and country planning, housing and national heritage (DGATLP), and the General Direction of Agriculture (DGA). One notes that the competences regarding environment, land use planning and agriculture are spread over three different General Directions24.

Several consulting bodies exist at regional level. For instance, the ‘&RPPLVVLRQ 5pJLRQDOH G¶$PpQDJHPHQW GX 7HUULWRLUH’ or CRAT (Regional commission for land use planning) is a multisectoral consulting body which advises the Walloon government on matters pertaining to land use planning. Other consulting bodies cover the fields of forestry (&RQVHLO 6XSpULHXU ZDOORQ GH OD IRUrW HW GH OD )LOLqUHERLV) and nature conservation (&RQVHLOVXSpULHXUZDOORQGHODFRQVHUYDWLRQGHODQDWXUH).

8.5.1.2 Provincial level The provinces are mainly decentralized institutions of both the federal and the regional government and are as such entrusted with a number of administrative tasks. The permit

24 At the political level, however, there is more integration: land use and environmental policies are the responsibilities of one Minister (OH 0LQLVWUH GH OD 5pJLRQ :DOORQQH SRXU O¶(DX O¶(QYLURQQHPHQW HW OD 9LH UXUDOH).

Legal Framework 133 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas granting powers of the provinces are more restricted in the Walloon region than in the Flemish region. For instance, the provinces in the Walloon region have no role in land use permit granting (SHUPLVG¶XUEDQLVPH and SHUPLVGHORWLU), the main responsibility for these aspects resting with the municipalities. As explained in more detail in the section on the Flemish region, the provinces can however wield some autonomous legislative power. The Walloon province involved in the Geul project is the Province de Liège.

8.5.1.3 Local level The municipalities have important tasks in land use planning at local level. They elaborate a 6FKpPD GH 6WUXFWXUH &RPPXQDO (Municipal Structure Scheme) and can define generally applicable rules and restrictions for land use, precising or altering the Regional Land Use Plans, by means of the 3ODQV &RPPXQDX[ G¶$PpQDJHPHQW (Municipal Land Use Plans). A consultative body at municipality level (‘&RPPLVVLRQ &RQVXOWDWLYH &RPPXQDOH G¶$PpQDJHPHQWGXWHUULWRLUH (CCAT)’ or Municipal Consulting Commission on Land Use Planning advises the municipal authorities on matters pertaining to the elaboration of Municipal Land Use plans or Municipal structure schemes. This Commission is composed of members of the public who have introduced their candidacy to be member of such a commission. Since 1995, the municipalities also have the authority to define additional protective measures in the field of nature conservation, providing these measures are in line with, and more severe than, regional nature conservation legislation. Moreover, municipalities are encouraged (by subsidies, among others) to define their own Municipal Nature Development Plan (3ODQ&RPPXQDOGH'pYHORSSHPHQWGHOD1DWXUH or PCDN). The local population can, to a certain extent, influence the decisions as to proposed major infrastructure works via the requirement for public consultation within the framework of environmental and “urbanistic” (formerly “building”) permitting and more specifically in the context of Environmental Impact Assessments (EIA’s) for such projects.

At the local level, of course, one also finds the major stakeholders concerned with flood and erosion control projects: on one hand, the people at the UHFHLYLQJ end of flood and erosion problems (landlords and farmers having property in flood-prone areas, residing tourists...); on the other hand the people whose land use practices can LQIOXHQFH to a large extent the downstream problems, but who are, themselves, not necessarily affected by them. For both categories, it holds true that existing negative land use practices and habits (e.g. building in flood-prone areas) are often enhanced or maintained by an absence of pertinent legislation (e.g. insufficient legal protection of wetlands) or an insufficient enforcement of the legislation, where it exists.

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8.5.2 Instruments

8.5.2.1 Water-resources management As in the Flemish Region, the basic law of 196725 still mainly settles the management of the unnavigable watercourses in the Walloon Region. Our Walloon informant emphasized the focus of this law on maintaining, modifying and adjusting the SHUPDQHQW riverbed. He also emphasized that applying this basic law to the letter, should mean establishing a better runoff or flow in the river system26; or quite contradictory to the upset of this Geul project. The basic law of 1967 has been complemented with a Royal Decree (‘$UUrWp UR\DO SRUWDQW UqJOHPHQW GH SROLFH GHV FRXUV G¶HDX QRQ QDYLJDEOHV’, 05.08.1970) and with provincial regulations (5qJOHPHQW SURYLQFLDO VXU OHV FRXUV G¶HDX QRQQDYLJDEOHV, drawn up by the &RQVHLOSURYLQFLDO).

Unnavigable watercourses of first category are managed by the ‘'LUHFWLRQ GHV &RXUV G¶(DXQRQQDYLJDEOHV’ of the ‘'LYLVLRQGHO¶(DX’ (DGRNE), unnavigable watercourses of second category by the Permanent Deputation of the Province and unnavigable watercourses of third category by the Municipal Council of the involved communities (under supervision of the Province). Landowners must take care of non-classified unnavigable watercourses in case the watercourse flows on, or along, their territory. Modifications and improvements on unnavigable watercourses of second and third category have to be advised and approved by the provincial authorities (the Permanent Deputation). A municipality must realize extraordinary works on unnavigable watercourses of third category according to the respective provincial regulations. The Province does not provide subsidies. The Ministry of the Walloon region may grant subsidies for ‘improvements’ on the watercourse (neither ordinary maintenance works (e.g. dredging), nor modifications will be subsidised). One can consult the categorical subdivision of the unnavigable watercourses in the ‘$WODV GHV FRXUV G¶HDX QRQ QDYLJDEOHV’ at the ‘6HUYLFHWHFKQLTXHGHOD3URYLQFH’ (A.R. du 30.09.1969). The Walloon part of the Geul river is classified as an unnavigable watercourse of second category, hence being managed by the Province of Liège.

The Walloon Region currently promotes the construction of storage reservoirs and spillways, which are considered as extraordinary improvements on the watercourse. A spillway must be planned in the 3ODQ &RPPXQDO *pQpUDO G¶(JRXWWDJH (see below), is owned by the municipality and its dimensions depend on the actual sewerage system. A storage reservoir will be dimensioned based on the results of a hydraulic study (for instance as provided for in this current Geul project). The Walloon government may grant subsidies to municipalities and provinces in case they need to expropriate and buy up a privately owned parcel of land for the construction of such a storage reservoir. However, due to the stringent soil legislation in the Walloon Region, there are problems

25 ‘/RLGXUHODWLYHDX[FRXUVG¶HDXQRQQDYLJDEOHVPRGLILpHSDUODORLGXMXLOOHWUHODWLYH DXUHPHPEUHPHQWOpJDOGHVELHQUXUDX[ 0% HWSDUODORLGXIpYULHU 0% ’ 26The law of 1967 was specifically directed towards drainage to improve agricultural practice along unnavigable watercourses (or contrary to the environment-friendly target!).

Legal Framework 135 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas concerning the dredging of the storage basins. The same soil legislation is responsible for the low presence of sediment traps in the Walloon Region. This, of course, does count especially for the policy regarding erosion reduction, and does not count for much regarding increased water retention. Sediment traps in the upstream catchment, however, do help avoiding severe mudflows in the urban area during high rainfall events.

The decree of 1970 declares, among other things, a ban on cultivating, building and pasturing the 0.5 m border along a watercourse. The Walloon government updated the decree in 1985 (‘$UUrWpGHO¶H[pFXWLI5pJLRQDO:DOORQPRGLILDQWO¶DUUrWpUR\DOGXDR€W  SRUWDQW UqJOHPHQW JpQpUDOH GH SROLFH GHV FRXUV G¶HDX QRQ QDYLJDEOHV’, 30.01.1985). Building on the land along an unnavigable watercourse is not forbidden in the Walloon Region, provided that a construction licence is granted. Building on floodplains, or flood- prone areas, however will not be allowed. In general, if the $GPLQLVWUDWLRQ&RPPXQDOH or the 'LUHFWLRQ SURYLQFLDO GH O¶XUEDQLVPH need to decide on granting a licence (for construction or reallotment…) concerning a domain along a watercourse, they have to consult the 6HUYLFH H[WpULHXU of the 'LUHFWLRQ GHV FRXUV G¶HDX QRQ QDYLJDEOHV or the 6HUYLFH WHFKQLTXH SURYLQFLDO (for watercourses of first/second or third category respectively). They will be given an unfavourable advice if the considered domain is situated in a flood-prone area (either defined or not by the 'LYLVLRQGHO¶(DX). The land along a watercourse could alternatively be protected from building by means of the ‘ORLVXUOHVGLJXHV’ (18/06/1979), which concerns among other things the protection of the hinterland.

The provincial regulations must be approved by the Walloon government and are published in the 0pPRULDO $GPLQLVWUDWLI. Among other things, the 5qJOHPHQWSURYLQFLDO identifies the rules regarding ordinary maintenance works (what to do, terms…), imposes a yearly control visit to all classified unnavigable watercourses (by the $GPLQLVWUDWLRQV &RPPXQDOHV and the 6HUYLFH 7HFKQLTXH 3URYLQFLDO), explains the procedures for obtaining a licence to perform modifications and improvements (extraordinary works) on unnavigable watercourses (for instance a licence is needed for constructing a storage basin), and declares some police rules (imposed minimum distance between the watercourse and plantations along this watercourse, prohibition on planting trees along the watercourse without being authorized by the Municipal Council…). Violation of this 5qJOHPHQWSURYLQFLDO will be penalized. An extract out of the Règlement provincial of the Province of Liège is given below: “Article 38: il est défendu de construire des murs ou des bâtiments, de planter des arbres en bordure des cours d’eau sans autorisaton préalable du Conseil communal, qui fixe l’alignement sur avis de l’Ingénieur en chef-Directeur du Service Technique Provincial, sauf recours à la Députation permanente. Pour les plantations, cet alignement est fixé à 3 m de la crête de la berge du cours d’eau. Cette distance est portée à 6 m dans le cas d’une plantation résineux.”

Special regulations exist as regards the distance between unnavigable watercourses and touristic infrastructure (e.g. camping sites, caravan parks, holiday centres…). For

Legal Framework 136 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas instance, a ‘free border’ (no infrastructure) of 8 m must be maintained between a camping site (FDPSLQJFDUDYDQLQJ) and a watercourse (measured from the riverbank or from the averaged high water mark). The infrastructure-free border can even be increased up to 15 m or more. Touristic infrastructure may on no account be located in flood-prone areas. ('pFUHWGX&RQVHLOGHOD&RPPXQDXWpIUDQoDLVHGXUHODWLI DX[FRQGLWLRQVG¶H[SORLWDWLRQGHVWHUUDLQVGHFDPSLQJFDUDYDQLQJ.)

In the near future, all Walloon municipalities are obliged to have a municipal drainage plan, or, ‘3ODQ&RPPXQDO*pQpUDOG¶(JRXWWDJH’. A drainage plan indicates the areas in the community having collective water treatment, the areas having individual water treatment and the involved infrastructure (sewage treatment plants, spillways, retention reservoirs, dispersion drain pipes…). After the PCGE being approved, the Municipal Council must draw up municipal sewerage regulations and an implementation programme for the PCGE. Every other year, the municipality has to report to the 0LQLVWqUH GH O¶(QYLURQQHPHQW GHV 5HVVRXUFHV QDWXUHOOHV HW GH O¶$JULFXOWXUH. The Walloon government can provide subsidies ($UUrWpGX*RXYHUQHPHQWZDOORQUHODWLIjOD VXEVLGLDWLRQGHVSODQVFRPPXQDX[JpQpUDX[G¶pJRXWWDJH, 23.06.1994). The PCGE and the municipal sewerage regulations are included in the present inventory because of their sensitisation and awareness-raising opportunities.

Since 1993, the Walloon Region can enter into so-called ‘river contracts’ (&RQWUDW GH 27 5LYLqUH) . A municipality should apply for it. A river contract is an agreement between all public and private actors in a catchment basin (representatives of sewage treatment plants, of the agricultural sector, of the municipalities, the Province, nature organisations…); aimed at reconciling the different functions of a river, of the riverbanks and of the water stored in the considered basin. Currently, there are eight standing contracts; there is no &RQWUDWGHULYLqUH for the Geul river yet. Each contract should reflect two main principles: 1. aiming at an integral, or complete, approach of the watercourse; 2. participation of, and cooperation with, all actors involved. Entering into a river contract comprises, except for consensus forming between politics, social life, economy, science and others, several goals that could be of relevance in the current Geul project, for instance: • integrating the ‘water’ dimension in the policy concerning land use planning, agriculture, industry, tourism, environment…; • affecting the behaviour and attitude of water users and managers: A river contract requires sensitisation, information and cooperation of all actors in the contract area, in order to establish a sustainable and integral water-resources management. A ‘follow-up’ committee must observe the implementation of each

27 &LUFXODLUHPLQLVWpULHOOHUHODWLYHDX[FRQGLWLRQVG¶DFFHSWDELOLWpHWDX[PRGDOLWpVG¶pODERUDWLRQGHVFRQWUDWV GHULYLqUHHQ5pJLRQZDOORQQHPRGLILpHSDUODFLUFXODLUHGXMXLQHWGXMXLQ, 18.03.1993

Legal Framework 137 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas contract. Municipalities, provinces and the Walloon Region can subsidise the necessary works as proposed for in the river contract. The regional subsidy is granted for the duration of the agreement, but however restricted to the total amount of money allocated by the municipalities and provinces.

The project area neither belongs to a ‘3ROGHU’ nor a ‘:DWHULQJXH’.

8.5.2.2 Land use planning The existing body of legislation on land use planning in the Walloon region is contained in the &RGH :DOORQ GH O¶$PpQDJHPHQW GX 7HUULWRLUH GH O¶8UEDQLVPH HW GX 3DWULPRLQH (CWATUP) or Code of land use planning, town planning and national heritage. This code contains several basic decrees and their application texts, the latter being the tools that should translate the decrees into measures and allow for the realisation of the regional policy objectives. Several tools can and are being used in the framework of attaining the overall objective of the Code, being “to satisfy in a sustainable way the social, economic, environmental and patrimonial needs of the collectivity”.

Planning tools: The outlines of the Walloon land use planning policy are defined in the 6FKpPD GH 'pYHORSSHPHQW GH O¶(VSDFH 5pJLRQDO or SDER (Regional Territorial Development Scheme). This is an indicative planning tool that, among many other things, defines the conceptual framework for the Regional Land Use Plans (SODQV GH VHFWHXU) and the municipal land use plans (3ODQV&RPPXQDX[G¶$PpQDJHPHQW). At municipal level, the ‘6FKpPDVGH6WUXFWXUH&RPPXQDO’ (SSC) have a similar role as the SDER, forming the inspiration for the municipal land use plans. A municipality is however not obliged to elaborate a SSC. Neither the SDER nor the SSC have a legislative value.

Legislative tools that define and fix the land use: 1. Land use plans More pertinent land use rules and restrictions are defined in the land use plans (SODQVGH VHFWHXU). Land use plans are spatial planning instruments. They allow defining rules and restrictions for land use on set and clearly defined areas. An environmental impact assessment ((WXGH G¶LQFLGHQFHV VXU O¶HQYLURQQHPHQW or EIE) is often required for changes to existing land use plans.

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The decree of 27/11/1997 has introduced into the Walloon legislation the division between areas scheduled for urbanisation28 and areas for which this is not the case. The latter include agricultural areas, forest areas, green areas, parks and nature reserves. The functional definitions of these areas can include uses complimentary with the main function: for instance agricultural areas are formally defined as having a role to play in the creation and the preservation of the landscape. Likewise, forestry areas have as additional function to preserve the landscape and the ecological equilibrium. Apart from the main divisions, additional zones with specific characteristics can be delineated on the Land Use Plans. This is the case, among others, for areas where natural risks can be expected. One of the areas that satisfy this definition are the flood- prone areas in river valleys. The CWATUP specifically prohibits transforming (via the revision of land use plans) areas not intended for urbanisation into areas where urbanisation is a possibility, whenever these areas are catalogued as areas where natural risks can be expected.

2. Site protection Site protection (‘FODVVHPHQWGHVVLWHV’) is a tool used in land use planning to preserve characteristic and homogeneous areas and landscapes. This label allows for the protection of hedgerows, forests and wetlands within the limits of the classified sites.

3. 3ODQVFRPPXQDX[G¶DPpQDJHPHQW (PCA) These are local tools that allow to better define, adapt or even change (under certain restrictions) the land use as defined by the (regional) land use plans.

4. 3HUPLVG¶XUEDQLVPH(land use permits) Formerly called building permits, these permits cover a larger field. For instance, the following activities are also covered by the land use permitting system: • afforestation of an agricultural area • deforestation of an area • changes to the topography of an area (note that this definition can and is being applied to works entailing the modification of riverbeds or banks, as well as to the construction of even minor ponds, basins, dikes, levees...) • cutting of individual trees in green areas • cutting of remarkable trees or hedgerows, in so far as they figure on a list defined by the Government. • changing the vegetation of moors and heaths

28 In the large sense of all uses not related to agriculture, forestry and nature conservation; quarrying, for instance, is considered a form of urbanization.

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Land use or allotment permits (SHUPLVGHORWLU) are subject to a number of regulations, both at the regional and the municipal level. These regulations intend to ensure that the constructions satisfy certain conditions regarding quality, aesthetic value, accessibility and so on. Security is also a factor: land use permits are excluded or subjected to a number of restrictions in areas where a major natural risk exists, such as flood-prone areas. Holiday villages have to comply to a specific set of rules, among which the requirement, along a watercourse, to leave free of any construction a border of 20 meter wide from the average high water mark, and the requirement to ensure total surface water drainage of the area. Additionally, the construction of residential weekend parks is specifically forbidden in flood-prone areas.

8.5.2.3 Agricultural policy Agriculture and agricultural policy is mainly a federal competence in Belgium. Nevertheless, the regions do have some powers in this field. Within the framework of the present study, two aspects are worth mentioning:

1. Agro-environmental subsidies This item is covered by a recent decision of the Walloon government (March 11, 1999). This decision defines a list of eleven agricultural practices that are considered an essential part of a sustainable and environment-friendly farming approach and as such eligible for subsidies. The following practices are of relevance within the framework of the current study: • Creation of grassed strips and turnaround strips: - Creation of low-input grassed strips, 4 to 20 meters wide, along the field edges; - Creation of cropped strips, 4 to 20 meters wide, along field borders, subjected to a low-input cultivation method, in contrast to the method applied to the remainder of the field; - Creation of grassland strips, 8 to 20 meters wide along water courses and orchards; • Conservation and maintenance of small landscape and biodiversity elements such as hedgerows, tree lines, wooded strips and ponds; • Seeding of a soil cover crop between two main growing seasons such as to maintain a soil cover as permanent as possible; • Low-input management of humid grasslands, excluding drainage.

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2. Land consolidation projects Land consolidation projects are intended to minimise agricultural production costs in rural areas, by optimising land allotment patterns and carrying out necessary infrastructure works (rural roads, drainage works…). At the same time, these projects offer the opportunity to enhance the ecological quality of the rural landscape and to maximise the soil and water conservation functions of certain ecosystems.

Since 1977, the land consolidation legislation imposes the drafting of a land evaluation plan (3ODQ G¶pYDOXDWLRQ GHV VLWHV) prior to any land consolidation project. This plan consists of an inventory and a valuation of all natural riches in the area. This inventory can serve as a reference and as the basis for assessing the suitability of any proposed intervention, from an environmental-conservationist point of view. The drafting of this plan is subsidised for the full 100% by the Walloon Region.

In a next step land organization plans (3ODQVG¶DPpQDJHPHQWGHVVLWHV) can be drafted, though this is not compulsory under the current legislation. These plans define the limits imposed on specific activities within the framework of land consolidation projects in the area, with the intent of protecting or enhancing its natural values. They define the “do’s and don’ts” and serve as a general guide and an environmental framework for the land consolidation project. Land consolidation committees receive an 80% subsidy from the Walloon Region towards the costs of drafting the plan.

The result of this integrated approach has been that in recent years, much more than before, land consolidation projects have taken the opportunity of maintaining or even enhancing valuable natural elements that play an important role in soil and water conservation, such as ponds, wetlands, and hedgerows. Moreover, infrastructure works like rural roads can and are being designed in such a way as to control runoff, while others are being constructed specifically with this purpose in mind (flood control basins, artificial wetlands…). This renewed approach to land consolidation, while still focused on improving conditions for agriculture, nevertheless has come to recognise the role of natural landscape elements in soil and water management and thus their contribution to a sustainable agriculture.

8.5.2.4 Environmental Policy 1. Pertaining to water resources management Water resources management in the Walloon Region has been dealt with earlier in this Chapter. Note that certain types of works such as drainage works or riverbed regulation can, in accordance with European law, be subjected to an environmental impact assessment. An EIA is required in any case for the creation of an impoundment if the water area exceeds 1 ha in sensible areas (10 ha in other areas).

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There is no specific and integrated legal tool that protects valley bottom wetlands as a whole, although texts conferring partial protection can be found in a number of legislations. Examples are: • the provisions in the land use planning legislation, concerned mainly with the protection of assets in flood-prone areas as well as the restrictions concerning touristic constructions along river banks (see above); • the interdiction to plant resinous trees (specifically fir trees) less than six meters from a river bank; • the interdiction to drive motorized vehicles on riverbanks,...

2. Pertaining to protection and management of forest resources and ecosystems The main legal basis for forest management in the Walloon region is the &RGH)RUHVWLHU of 1854, amended and updated a great number of times since. The power of this code, which deals mainly with the economic aspects of forest management, does only partially extend to privately owned forests. All forests though are subject to clear restrictions as regards cutting, land clearing and extraction of litter, humus or other soil components. Special management directives (imposing, among others, limitations to clearing and land drainage) have been developed for selected zones such as impoundment watersheds, valley bottoms and source areas.

The code specifies a number of cases for which subsidies can be requested. It concerns activities aiming at: • the improvement of the forest patrimony, which includes subsidies for the afforestation of agricultural lands; • the opening of forests to tourism and recreation; • forest protection and restoration; • awareness-raising of the public to the economical, social, ecological and protecting function of a forest.

Forest improvement requiring drainage works is not eligible for subsidising, as this practice is considered contrary to the policy that forests should contribute to regulation of the water cycle. Note that the Walloon region subsidises the planting of hedgerows composed of indigenous species, on condition that the recipient of the subsidy accepts to maintain the hedgerows during a 20-year period29.

29 Arrêté du Gouvernement wallon relatif à l’octroi d’une subvention pour la plantation de haies du 9 février 1995

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In privately owned forests, the 6HUYLFHGHV(DX[HW)RUrWV can, on the basis of a special law (law of 28 December 1931) forbid massive clearing if the forest has a clear function in soil stabilisation on steep slopes. Remember that any forest clearing (if not followed by replanting of trees) requires a ‘SHUPLVG¶XUEDQLVPH’ within the framework of the land use legislation and that the same holds for planting of trees outside forest areas. Afforestation of non-forest areas can also be subjected to the requirement of an EIA under the relevant legislation, if negative ecological impacts are suspected.

The ecological value of forests is recognised through the Nature Conservation Law (/RL VXUODFRQVHUYDWLRQGHOD1DWXUH(1973) and its many modifications) that has introduced the notion of forest reserves and nature reserves. Theoretically, this law allows for the expropriation of privately owned lands if such is in the interest of nature conservation (Art.6, par.4). On the other hand, private organisations can be subsidised for the acquisition of land intended for the creation of nature reserves. In nature reserves, it is forbidden, among many other things, to dig, quarry, change the natural soil level and influence the ground water and surface water regime. Restrictions for forest reserves are less stringent. Article 37 of the law allows measures to be taken (including subsidies) in the interest of nature conservation, that favour the protection of vegetation on steep slopes and the protection of vegetation along rivers. Article 58 states that it is forbidden to install drainage ditches in areas defined as nature zones, or nature reserves by the regional Land Use Plans.

Special protection is conferred to wetlands (]RQHVKXPLGHV) since 1989 ($UUrWpUHODWLIj OD SURWHFWLRQ GHV ]RQHV KXPLGHV G¶LQWpUrW ELRORJLTXH), in as far as the ecological and scientific value of a particular wetland is officially recognised. While this text recognises the basic role that wetlands have to play in regulating the hydrological cycle, it is mainly concerned with conservation of species of fauna and flora within wetlands, not with habitat preservation as such. Other protected areas, in line with European Union legislation, are the Special Protection Zones and Special Conservation Zones or “Habitat” areas.

8.5.3 The applicability matrix The applicability matrix (Table 8.6) compares the instruments as mentioned in part 8.5.2 against several potential flash floods reducing measures (potentially applicable technical measures, simulated in Chapters 6 and 7). The matrix gives an idea about the relevance and the applicability of each instrument with respect to water retention purposes. A distinction was made between instruments which are: () applicable (already enforced – symbol used in the applicability matrix is ‘’), () possibly applicable (needs further investigation and elaboration – symbol used in the matrix is ‘’), () not applicable (can not be used in this framework – QR V\PERO in the applicability matrix) and ()

Legal Framework 143 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas instruments which are not meant for water retention purposes at first, but which could have an indirect positive effect on flash floods reduction while being used for another purpose (symbol in the matrix is ‘L’). The matrix in Table 8.6 also indicates the time frame over which instruments could be used to implement a measure; a distinction was made between short term (0-5 years), middle long term (5-10 years) and long term (10-15 years). The availability of financial resources and whether usage of the instruments is based on a voluntary basis are also indicated.

Table 8.6 Applicability matrix for the Walloon legal framework 30

0HDVXUHV,QVWUXPHQWV Water-resources management Water-resources d’Egouttage Général Plan Communal rivière de Contrat plans use land Regional Site protection plans use land Municipal permits Land use subsidies Agro-environmental projects Land consolidation Decree Forest conservation nature on Law Policy of sensitisation and awareness-raising 0 0 + i 0 0 i i Incentives policy + 0 + i i i Adjustment of riverbed 0 0 (Re-) allocation of the riverbed 0 0 Creation of wetlands 0 0 0 i i i i 0 i 0 Ground cover and limited fallow 0 + 0 0 Turn high sloping areas to grassland/wood 0 i i i i + + Re-introduction of hedgerows/green belts 0 i + 0 Principles of sustainable farming 0 + Land retirement 0 i 0 0 Adjustment of parcelling i Storage basin (river/upstream) 0 0 0

3HULRG (l=long; s=short; m=middle long term) ssmlmmssmlm )LQDQFLDOUHVRXUFHV (y=yes; n=no) yyyyyyyyyyy 9ROXQWDU\ (y=yes; n=no) yyy/nnnnnynny

30 At this point, the term ‘water-resources management’ covers the basic law of 1967 concerning the unnavigable watercourses, the decree of 1970, the ‘loi sur les digues’. and the provincial regulations

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As can be seen from the above table, the potential flash flood reducing measures selected in the present study are to a greater or lesser extent supported or enhanced by the existing legal framework:

Sensitisation and awareness-raising to the need for water retention in the watershed can most effectively be implemented within the framework of interventions that clearly contribute to reaching this goal. For instance, DJURHQYLURQPHQWDOVXEVLGLHV don’t always have water retention objectives as their primary goal, and this is even less the case for ODQGFRQVROLGDWLRQSURMHFWV. Nevertheless, there is room for implementing measures that contribute to water retention within the framework of the said legal instruments, which makes them a good vehicle for awareness-raising. This is especially true for land consolidation projects, which are preceded by thorough preparation phases in which there is plenty of interaction between official instances and the farming community. Awareness-raising can also be done within the framework of the )RUHVW 'HFUHH; it specifically allows for the subsidizing of activities aimed at “awareness-raising of the public to the (…) ecological and protective function of the forest”. It seems logical that the role of forests in the hydrological cycle should also be treated under these activities. The VLWHSURWHFWLRQOHJLVODWLRQ and the ODZRQQDWXUHFRQVHUYDWLRQ (and more precisely the possibility to confer protection to certain wetlands) can also indirectly be vehicles for awareness-raising, by stressing the importance of regulation of the water cycle (next to ecological and esthetical values) as a secondary criterion in the decision to protect a site or a wetland. Sensitisation and awareness-raising towards enhanced water retention in the catchment basin could be implemented within the current ZDWHUPDQDJHPHQWSROLF\. The Walloon Government and the Province, for instance, do promote the construction of water storage reservoirs (‘extraordinary improvements on the watercourse’); the PCGE may contain special regulations that point at increased infiltration or at the construction of dispersion drain pipes instead of ordinary drain pipes. Building on the watercourse borders is not advisable (e.g. distance regulations, ORL VXU OHV GLJXHV). The mentioned instruments however, still need some modifications or supplementations GLUHFWO\ or specifically focusing on the need of enhanced water retention in (the upstream parts of) the catchment. A river contract may contribute considerably to enhanced sensitisation, being a prerequisite in handling the problem. All stakeholders and actors are involved, and the contract directly aims at affecting the behaviour of policy-makers and land- and water users in the region in order to perform ‘integral water management’.

Financial incentives to implementing water retention measures in the watershed can be found in a number of legislations and regulations. For instance, in subsidising the construction of storage reservoirs (ZDWHUUHVRXUFHVSROLF\). However, water retention is often only a secondary purpose or an indirect outcome of measures implemented in the pursuit of other objectives. The DJURHQYLURQPHQWDO VXEVLGLHV are a clear example: creation of grassed strips, seeding of a soil cover (both essentially anti-erosion measures), conservation of hedgerows, wooded strips and ponds (intended mainly to maintain biodiversity) as well as the conservation of humid grasslands all can contribute

Legal Framework 145 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas to less, or to more evenly distributed, runoff; and all of these measures are eligible for subsidies. The IRUHVWGHFUHH allows for the subsidising of activities aimed at “the improvement of the forest patrimony”, which also covers the afforestation of agricultural lands and thus the extension of forested area in a given watershed. Finally, the ODZ RQ QDWXUH FRQVHUYDWLRQ makes it possible to subsidize private organisations for the acquisition of land intended for the creation of nature reserves. This measure can indirectly contribute to a better water retention in the watershed as a whole if one assumes that areas subjected to “natural” management have better water retention capacities than agricultural areas.

If the extraordinary modifications and improvements on unnavigable watercourses (in the EDVLF ODZ RI ) are interpreted to improve the water flow within the context of ‘integral water management at catchment level’, adjustments of the riverbed will be performed to slow down the water flow. For instance, constriction devices could be installed to locally obstruct the river water flow. Of course, this requires a storage reservoir (e.g. retention basin, floodplain, wetlands). As a river contract aims at reconciling the functions of the river, the riverbank and the water stored in the river catchment basin, adjustments of the riverbed to enhance water retention could be proposed to fulfil this aim.

The EDVLFODZRI focuses on riverbank protection and therefore often prevents the repositioning of the actual course – the bed – of the river. The &RGH&LYLO, on the other hand, points at ‘ODLVVH] IDLUH OD ULYLqUH’, or thus at freely meandering. According to the land use type of the area a river flows through, the one or the other regulation will be implemented. For instance, in urban areas a watercourse will often be embanked; whereas in pastureland the watercourse will be allowed to freely meander. Re-allocation of the riverbed, in order to slow down the water flow, can be implemented within the current water-resources policy. It is still of paramount importance that a sound land use planning is established, and that the ‘water dimension’ is fully integrated or even a directive in this land use planning (cf. the river contracts).

A number of existing legislations or legislative tools are relevant where the creation or conservation of wetlands is concerned. The CWATUP limits the revision of ODQG XVH SODQV if such revision would result in the (potential) urbanisation of existing flood-prone areas. The power of the municipalities to change, via the PXQLFLSDOODQGXVHSODQV, the land use as defined by the regional land use plans, could theoretically also affect the conservation of wetlands. /DQGXVHSHUPLWV are subjected to a number of restrictions in flood-prone areas. In this context, it should also be mentioned that changes to the topography of an area require a land use permit; the creation of wetlands that would require the construction of even small levees could as such be subjected to the permitting process.

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6LWHSURWHFWLRQ allows for the protection and thus the conservation of wetlands within the limits of a classified site. The IRUHVW GHFUHH also has an indirect impact on the preservation of natural wetlands, as it limits drainage in selected forested areas (valley bottoms, source areas) and does not subsidise forest improvement activities that require drainage. /DQG FRQVROLGDWLRQ SURMHFWV are more directly concerned with the creation of artificial wetlands, if such can be done within the framework of the larger objective to improve water management in a given area (ZDWHUUHVRXUFHV SROLF\). Artificial storage basins intended to control runoff can and are effectively being implemented in the form of wetlands. Finally, the ODZRQQDWXUHFRQVHUYDWLRQ prohibits the drainage of nature zones and nature reserves and allows for the protection of wetlands. The latter is only possible if the said wetland has a recognised ecological and scientific value, which restricts the applicability of this measure for the primary objective of water retention in the watershed.

Due to its integrated approach of a water course, the ULYHU FRQWUDFW appears to be a highly valuable and favourable tool for proposing all kinds of water retention enhancing measures; measures to slow down the water flow (also concerning the policy on land use planning, the environmental policy: creation of wetlands, cultivation of green belts, planting of hedgerows, providing for ground cover etc.). Of course, the proposed measures need to be implemented as well. A follow-up committee has to watch the execution of the works.

Maintenance of permanent ground cover is most effectively implemented under the provision for DJURHFRORJLFDOVXEVLGLHV, which makes it possible to subsidize the seeding of a soil cover crop between two main growing seasons as well as the creation or conservation of grassed or wooded strips. Both the IRUHVWGHFUHH and the ODZRQQDWXUH FRQVHUYDWLRQ contribute to maintaining or even extending the area under permanent soil cover in a given watershed, by subsidising the afforestation of agricultural land and the acquisition of land for the creation of nature reserves. Note, however that the afforestation of agricultural areas requires in any case a ODQG XVH SHUPLW and in some cases even an HQYLURQPHQWDOLPSDFWDVVHVVPHQW

A number of legal texts have to be taken into consideration when the turning of high sloping areas into grassland or wood is concerned, first among them the IRUHVWGHFUHH that can subsidize afforestation schemes (again subject to obtaining a land use permit). The law of 28 December 1931 specifically forbids massive clearing of forests that have a clear function in the stabilisation of steep slopes. The /DZRQQDWXUHFRQVHUYDWLRQ allows for the protection of forests (and other permanent vegetation forms) on steep slopes as forest or nature reserves if these areas are recognised to have an important natural value. Moreover, the law specifically allows measures to be taken, including the granting of subsidies, which favour the protection of vegetation on steep slopes. 5HJLRQDO DQG PXQLFLSDOODQGXVHSODQV can contribute to the afforestation of steep slopes by setting these areas aside as nature zones, nature reserves or forestry zones. 6LWH SURWHFWLRQ

Legal Framework 147 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas can cover large parts of a given watershed and protect forests within the boundaries of the protected sites, on condition that the forests are part of a typical landscape worth protecting.

Introduction of hedgerows or green belts (or the conservation of said elements) is specifically covered by the legislation on DJURHQYLURQPHQWDOVXEVLGLHV which subsidizes the conservation and maintenance of hedgerows, tree lines and wooded strips. /DQG FRQVROLGDWLRQSURMHFWV can contribute to the preservation of hedgerows if the initial land evaluation plan has identified them as a valuable element. Cutting of hedgerows also requires a ODQGXVHSHUPLW, but only if they are identified as being valuable and as such figure on a list compiled by the government.

The principles of sustainable farming are favoured by the system of DJURHQYLURQPHQWDO VXEVLGLHV, which form an incentive program accessible to all farmers and not limited to certain regions or areas.

Land retirement is actively made possible by both the IRUHVW GHFUHH and the ODZ RQ QDWXUHFRQVHUYDWLRQ. The former subsidizes the reforestation of agricultural land (subject to a land use permit); the latter allows for the expropriation of privately owned land in the interest of nature conservation and subsidizes the acquisition of land intended for the creation of nature reserves.

Adjustment of parcelling is frequently carried out within the framework of ODQG FRQVROLGDWLRQSURMHFWV. Its primary objective is however to optimise working conditions for agriculture, not to maximize water retention in the watershed. It should be ascertained on a case-by-case basis if both objectives are compatible in a given situation.

Storage basins can be realized (artificial) or identified (wetlands, floodplains) within the current water management policy.

8.5.4 Conclusions on the Walloon legal framework As shown in the preceding paragraphs, most of the proposed measures fit in the framework of at least one legislative tool and no major contradictions between proposed measures and existing legislation have been identified. Crippling contradictions between legislations have not been found either, although many differences in focus can be found, for instance between the forest decree which actively sustains afforestation of agricultural land by subsidizing it, and the land use and environmental legislation which limit its appeal by requiring a land use permit and in some instances even an environmental impact assessment.

Legal Framework 148 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

As for the Dutch and the Flemish legislative framework, the same general conclusions can be drawn regarding the Walloon Region. No legislation provides a complete set of rules to sustain water retention at catchment level; limiting of runoff is usually no primary goal; and most relevant legislation does not have an area-based perspective. The only exceptions to this, almost by definition, are once more the land consolidation projects.

Especially the ODZ RQ QDWXUH FRQVHUYDWLRQ is rather disappointing in this respect. Its potential as a tool for land and water conservation is severely limited by its focus on species and habitat protection. Generally applicable rules for given forms of land use do hardly exist. The appeal of its potentially interesting measures is greatly limited by the fact that they have no general applicability: wetlands can only be protected if their ecological value has been recognised and the limitations the law sets on certain practices do only apply to areas identified as valuable by either the land use legislation or the nature conservation legislation

The IRUHVW OHJLVODWLRQ, although traditionally focused on the productive function of a forest, has a more general applicability. Although most of its forest-management related regulations do not extend to privately owned-forests, other measures and limitations are valid for all forests. The ODQG XVH OHJLVODWLRQ, although area-based and thus potentially appealing, is often not specific enough in its prescription of allowed or restricted uses for a specific land use class or does not link them to hydrological management. It would be advantageous if criteria related to water management at a basin level (minimising runoff, for instance) could be used to assess the suitability of a given form of land use in a given area. Especially the PXQLFLSDO ODQG XVH SODQV seem to have a scale that is perfectly adapted to contribute to the objective of water retention.

The current legislation and policy regarding ZDWHUUHVRXUFHV PDQDJHPHQW could be applied in the Walloon Region to enhance water retention in the Geul watershed and slow down the river water flow, if the awareness of the need of this is thoroughly founded among Walloon policy makers and land users. People must be aware that a sound management of the upstream parts of the Geul catchment could considerably reduce the damage caused by flash flood events and accompanying mudflows in the downstream parts. A catchment needs to be managed by means of an integrated approach: a river basin does neither stop at the borders of the riverbed, nor at the borders of a country. The Walloon government gave the initial impetus to this awareness-raising by introducing the ULYHU FRQWUDFWV. Unfortunately, there are only eight standing river contracts at the moment in the Walloon Region and the Geul river is not yet considered. Besides, although the initiative of the river contracts being admirable, the determination of regulations and the execution of these regulations often still depends on the goodwill of the involved parties. A more stringent legislative framework to support not only the up- set of a river contract, but also its implementation, should be established. Furthermore, if the basic law of 1967 were to be interpreted and implemented to the letter, environmentally sound measures wouldn’t make a chance in the Geul catchment and only the minor riverbed would be considered. Potential revisions of the legislation concerning unnavigable watercourses should pay particular attention to this point.

Legal Framework 149 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

However, it is interesting to note that the legislations that seem to best sustain the proposed measures or at least have the potential to do so are both concerned with agriculture, not with nature or water conservation. /DQGFRQVROLGDWLRQSURMHFWV have an area approach and a scale that is ideally suited to implement many of the proposed measures. Although their primary goal is to optimise working conditions for agriculture, this does not exclude taking measures that favour water retention, and even provide the financial and technical means to do so. The system of DJURHFRORJLFDOVXEVLGLHV is also an attractive instrument that allows for the implementation of a number of the water retention measures proposed in the present study. Its effectiveness could be further enhanced by providing subsidies for measures specifically aimed at increasing water retention and by making it possible to differentiate the measures eligible for subsidies and even the amount of the subsidies on an area basis.

8.5.5 Recommendations for the Walloon region It has been noted that the existing legal instruments pertaining to water retention in a watershed are few and spread out over a number of sectorial legislations. Taken together, they do not form a consistent policy or translate into a consistent set of measures. The same holds for the institutional setting, which does not show a global and clearly assigned responsibility for matters pertaining to water management at basin level either, but rather a fragmented set of sometimes partially overlapping responsibilities at different levels of different administrations. This should not come as a surprise, since water management at basin level is not a separate policy field, contrary to for instance land use, environment and forestry. This situation, ultimately, reflects the importance society adheres to watershed management.

An integrated watershed management policy, although it would effectively allow for the solution of many of the problems encountered in the Geul catchment, is – however introduced by the river contracts – therefore not likely to be in operation within the near future. With this in mind, efforts should be directed at making possible minor but effective changes to the existing legislation, and to better co-ordinate actions between responsible administrations. This general remark translates into the following recommendations:

• Responsibility for the co-ordination of the different water management efforts carried out within the catchment should be assumed by a clearly defined institution, which preferably should also have the capacities and the funding to implement measures by itself. Ideally, this institution should take the form of an independent River Basin Authority, being able to operate at an interregional or even international level. Within the current institutional framework for the Walloon Region, one could imagine that either a modified “FRQWUDW GH ULYLqUH” (with stipulations regarding execution and implementation) be concluded for the Geul catchment, or that the Province of Liège assumes the required coordinating responsibility.

Legal Framework 150 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

• Contributing to the management of the natural surface water cycle in a catchment (e.g. limiting runoff in hilly regions) should become a declared side-objective of several of the existing legislations, the IRUHVW GHFUHH and the ODZ RQ QDWXUH FRQVHUYDWLRQ being the prime examples. Other possible instruments that offer opportunities for integrated watershed management that could restate their goals to include these added objectives are VLWH SURWHFWLRQ, and the practices of DJUR HQYLURQPHQWDOVXEVLGLHV and ODQGFRQVROLGDWLRQ. • The spatial focus of a number of existing regulations should be reconsidered. The power of a number of instruments contained in the law on nature conservation could be greatly improved if their field of application would extend beyond officially recognised protected areas. Moreover, it should be considered whether a spatial differentiation of existing legislation wouldn’t be advantageous in a number of cases: one could imagine, for instance, that the approach to land consolidation projects, forest management or nature conservation would be regulated to be different in watersheds which are known to be hydrologically sensitive, or that agro- environmental subsidies would be made more attractive in these areas. • Land use planning as an instrument should take into account, to a greater degree than it does now, the sensitivities of the different physical environments to land use. Land use planning at municipal level could become a powerful instrument to preserve and even create protective land use forms in sensitive areas of a given catchment. Moreover, in the land use permit legislation, certain catchments or parts of catchments should be labelled as “areas of natural risk” which would automatically restrict a number of land use forms in these areas.

 &RQFOXVLRQVDQGUHFRPPHQGDWLRQV Most of the proposed measures fit in the framework of at least one legislative tool and no major contradictions between proposed measures and existing legislation have been identified. This applies to both the Dutch, Flemish and Walloon part of the catchment. Crippling contradictions between legislations have not been found, although many differences in focus are present. What has been concluded or recommended on the three distinct parts in this legal framework study can be extrapolated for the catchment as a whole.

An integrated approach of the Geul catchment is needed; not only combining the points of view of different policy sectors (water-resources management, land use planning, environmental planning, agricultural sector…) and different levels in society (local, provincial and regional or national), but also taking into account the trans-national concerns. For instance, policy-makers and land users in the upstream parts of a trans- boundary catchment should be aware and convinced of taking measures to reduce the risk on flash flood events, and the accompanying mudflow damage, in the downstream part of the catchment (e.g. consciousness on retaining water in the catchment by enhanced infiltration (pastureland or forest instead of bare fields, less paved surface, dispersion drain pipes instead of ordinary drain pipes…), or on slowing down the water

Legal Framework 151 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas flow instead of accelerating it (storage reservoirs, constriction devices)). A sustainable and sound land use planning should be established in order to prevent building on flood- prone areas or introducing infrastructure along watercourses. After all, flooding events have always existed in the Geul river region and high rainfall events will always remain. The increasing dissatisfaction especially results from the fact that more and more sediments are carried along by the river (increased erosion due to, among other things, maladjusted agricultural practices and land use in the hilly loess region), which are deposited in often improperly planned urban area during (flash) flood events. The importance and need of considering the water system as a guiding principle in land use planning is obvious. An elaborated and sound trans-boundary (European) legislative framework and regulations (incentives, taxes) should facilitate both the water retention and erosion combating in the Geul catchment. A re-valuation of the actual land use in the socio- economic context should also be considered (for instance promotion of other crops, promotion and subsidizing of biologic (small-scale) agriculture). The reader is also referred to Annexe F.1, ‘Awareness-raising measures’, on this part.

The most obvious conclusion one can derive from the analysis of the legislative framework for the three regions is that no legislation provides a complete set of rules or a clear framework in which to place measures aimed at hydrological control on the river basin level. Measures do exist, but they are dispersed over a whole array of laws and regulations. More importantly, limiting the runoff is never a primary goal; it is a secondary result of measures that are primarily intended to conserve biodiversity, to combat erosion or to optimise conditions for agriculture. It should also be noted that most relevant legislation does not have an area-based perspective. This is regrettable, as such a perspective could make it possible to use its tools in a spatially integrated way or to apply them selectively to watersheds one wants to protect. The only exceptions to this, almost by definition, are the land consolidation projects. It is interesting to note that the legislations that seem to best sustain the proposed measures or at least have the potential to do so are both concerned with agriculture, not with nature or water conservation. Land consolidation projects for instance have an area approach and a scale that is ideally suited to implement many of the proposed measures. Although their primary goal is to optimise working conditions for agriculture, this does not exclude taking measures that favour water retention, and even provide the financial and technical means for doing so. The system of agro-ecological subsidies (following the European directive) is also an attractive instrument that allows for the implementation of a number of the water retention measures proposed in the present study. Its effectiveness could be further enhanced by providing subsidies for measures specifically aiming at increasing water retention and by making it possible to differentiate the measures eligible for subsidies and even the amount of the subsidies on an area basis.

Sensitisation and awareness-raising to the need for water retention in the watershed appear to be of paramount importance for implementing most of the inventoried measures, since the most promising measures do depend on the goodwill of the land

Legal Framework 152 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas users. If measures are to be implemented and sustained in practice, a bottom-up approach towards the selection of a measure, the location of the implementation of a measure etc. should be performed with all actors and stakeholders involved (participatory decision-making process).

The reader is also referred to §8.2.4 and §8.2.5 (The Netherlands), to §8.4.4 and 8.4.5 (Flemish Region) and to §8.5.4 and §8.5.5 (Walloon Region) for the conclusions, respectively recommendations, on the distinct parts in the Geul catchment.

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 &21&/86,216

This report presents the results of the SLORW SURMHFW (B4-3040/97/730/JNB/C4) IRU WKH GHILQLWLRQRIHQYLURQPHQWIULHQGO\PHDVXUHVWRUHGXFHWKHULVNIRUIODVKIORRGVLQWKH*HXO 5LYHUFDWFKPHQW %HOJLXPDQGWKH1HWKHUODQGV . The study is financed by the European Commission, Directorate-General Environment, and co-financed by the Walloon Regional Government, the Dutch Waterboard Roer & Overmaas and the Belgian Province of Limburg.

The overall goal of the project is to identify environment-friendly measures possibly applicable to reduce the risk of flash flood events in the Geul river catchment area, and to study their effectiveness. Within the scope of this overall goal, more specific objectives are defined: • Develop a methodology suitable to study the effectiveness of possibly applicable measures to reduce the risk of flash flood events at catchment scale, applicable in the Geul catchment area as well as in other European catchment areas; • Apply this methodology to study the Geul catchment area: - identify relevant information and acquire, standardise, store and supply this information to the project partners: WHUULWRULDOGDWDLQYHQWRU\; - perform a preliminary risk analysis; - bring the international stakeholders together and identify sets of possibly applicable measures to reduce the risk of flash flood events: VFHQDULR GHYHORSPHQW; - study the effectiveness of the scenarios to increase the water retention in the catchment and to reduce peaks in water flow to the river network: K\GURORJLFDO VWXG\; - study the effectiveness of the scenarios to reduce the water heights in the river network, relative to the height of the riverbanks: K\GURG\QDPLFVWXG\; - identify the most effective or favourable scenario or set of measures to reduce the risk of flash flood events; - study the effectiveness and applicability of the legal frameworks and policy instruments of local-, provincial- and national authorities to support the implementation of the most favourable set of measures to reduce the risk of flash flood events: OHJDOIUDPHZRUN. • Conclude on the effectiveness of the methodology to contribute to the development of environment-friendly policies of water management and flood risk reduction in the Geul catchment area; • Recommend, where necessary, how to ameliorate the methodology to be applicable in other European catchment areas.

Conclusions 154 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

Project partners originating from all countries located in the Geul river catchment, Belgium and the Netherlands, performed the study. Together they developed and executed an appropriate methodology. The methodology is based on a thorough analysis of a well-defined reference situation, namely the historic and current land use distribution, rainfall measurements and measured data on water flow through the Geul river network. The correct water flux simulation in this reference situation permits the simulation of water flow in hypothetical situations or scenarios. The regional stakeholders (the Walloon Regional Government, the Dutch Waterboard Roer & Overmaas and the Belgian and Dutch Provinces of Limburg) participated in the present study by providing the necessary information, input for further study, and by assisting in the decision-making process during the scenario development.

Five scenarios were developed for further study, including land use measures to be taken in the watershed and civil-technical measures to be taken in the river itself. CSO and FSAGx performed the territorial data inventory, harmonized the internationally acquired data into one format and developed a Geographical Information System (GIS) for data storage, data analysis and data input for the other study items. CSO also described the area and set the reference for further study by performing a preliminary analysis of the cause for land runoff. The University of Liège, in collaboration with the Unit of Agricultural Hydraulics FSAGx, performed the hydrological study. They analysed the effectiveness of the land use scenarios, simulating the amount, timing and location of runoff to the river network as a function of climate, hydrogeology, soil and land use scenario. Technum, in cooperation with IMDC, performed the hydrodynamic study. They analysed the effects of the land use scenarios, simulating the level and timing of water flowing through the river network as a function of the runoff, simulated in the hydrological study. The hydrodynamic simulation also served to analyse the effectiveness of scenarios of civil-technical measures, implemented in the upstream parts of the riverbed. Technum also studied the legal framework and was involved in the project management.

 &RQFOXVLRQVRQWKHWHUULWRULDOGDWDLQYHQWRU\ Relevant data were acquired in all three countries located in the Geul river catchment area (Belgium, The Netherlands and Germany). The internationally diversified sources of information were associated with considerably diversified classification systems (e.g. soil- and land-use classification), reference systems (e.g. units of measurement, geographic map projections and map co-ordinates) and storage formats. Consequently, data harmonisation was very time-consuming and led inevitably to additional uncertainties. It is therefore highly recommended to initialise a standardisation of geographic databases (GIS) with standardised and coherent data within European countries.

A Geographic Information System (GIS) was developed for data storage and further study (ZKLFKUHTXLUHVWKHH[SOLFLWDXWKRULVDWLRQRIWKH)6$*[DQGWKH6(7+< 6HUYLFH G¶pWXGHV GX 0LQLVWqUH ZDOORQ GH O¶(TXLSHPHQW HW GHV 7UDQVSRUWV  IRU WKH &$5+< GDWD

Conclusions 155 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

EDVH *,6). The ESRI software packages Arc-Info and ArcView were used for this purpose. The GIS includes a topographic map of the area, a soil map, an elevation map, a hydrological map and a current land use map. Secondary maps were derived from these base maps, including a hydrological soil group map, a slope map, a historical land use map of the 1950's etc. Dividing the GIS map layers into geographic grid-cells of 30x30m set the degree of detail. The GIS proved a valuable tool to perform geographic analyses.

 &RQFOXVLRQVRQWKHSUHOLPLQDU\ULVNDQDO\VLV The maps were used to describe the area and were used for a preliminary risk analysis. The analysis led to the determination of trends between the historic and current risk of runoff at catchment scale following two methods (simplified Wischmeier USLE method and the US SCS method). The USLE procedure implied a land use systems analysis, based on parameters derived from the Universal Soil Loss Equation. Literature review served to quantify the parameters explaining the risk of surface runoff in relation with sheet and rill erosion (including partly aspects of land erosion), slope and land use (land cover and land management practices). Besides these aspects, the SCS method also includes soil humidity and soil type.

The results suggested an increase of the risk of runoff on arable land. Although its acreage did not change since the 1950's, its contribution to the risk increased because of the increased proportion of weeded crops. The quantification of these risks is made in the hydrological analysis.

 &RQFOXVLRQVRQWKHSUHOLPLQDU\K\GURORJLFDODQDO\VLV FI$QQH[H' The analysis of the availability and reliability of rainfall and water discharge data (observations at meteorological and limnimetric stations) shows: • a limited number of pluviographs, affecting the knowledge of spatial distribution of hourly rainfall; • abnormally low or high values at some meteorological stations and periodically missing data.

Insofar as the basic data can be considered as being reliable, the preliminary hydrological analysis provides the following conclusions: • in general, mean annual flow and flow coefficients are small (around 30% or less, including during flood events) with respect to usual evapo-transpiration rates for this area; low annual flow coefficients for the tributaries of the Geul are observed, suggesting a "loss" of water;

Conclusions 156 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

• the flood rise time is short (2 to 4 hours in the central part of the basin; phase-lag of 4 to 10 hours at the outlet), related to the shape and topography of the watershed; • peak flows show normal values (200 l/s.km2 at Hommerich) but a damping of the peak flows is observed at the outlet (100 l/s.km2 at Meerssen).

 &RQFOXVLRQVRQWKHVFHQDULRGHYHORSPHQW A preliminary list of 46 possibly applicable measures to reduce the risk of flooding was established on the basis of literature review, preliminary analysis and brainstorm sessions. This number was reduced to a number of five scenarios, which were subject for further study. The regional stakeholders were involved in the identification-process of this limited number of scenarios.

Two reference scenarios were defined: the current and historical land use situation. The other three scenarios represent possibly applicable measures to reduce the risk of flooding from its current level to the “historic” level or even further. The project team expects that an integrated approach of water management at the catchment scale would significantly reduce the risk of flash flood events in downstream, flood-prone areas. The scenarios have an environmental dimension, reflecting interventions in the land use distribution to improve water retention in the catchment, and a civil-technical component, reflecting interventions in the riverbed itself to improve water retention in the upstream part of the river network. The scenarios, identified for simulation in the hydrological and hydrodynamic studies, were:

6FHQDULR /DQGPDQDJHPHQW 5LYHUPDQDJHPHQW . 1990 reference Present land use Present situation . Scenario 2 Grass on slopes >12% Increased roughness of the river flood plains . Scenario 3 Forest on slopes >10% Present situation . Scenario 4 Greenbelts / hedgerows Addition of 2 constriction devices in the riverbed .1950 reference Land use of the 1950’s Present situation

 &RQFOXVLRQVRQWKHK\GURORJLFDOVWXG\ The effectiveness of the land use scenarios to reduce the water runoff to the river network was studied in the hydrological study by means of a lumped dynamic simulation model (the hydrological part of the model MOHICAN, developed by ULg and FSAGx). The hydrological model is composed of a soil sub-model (EPIC-GRID) and a groundwater sub-model (which utilizes a groundwater impulse response transfer function). The model computes water fluxes from the soil to the river network, from the

Conclusions 157 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas soil to the groundwater, and from the groundwater to the river network (base flow). The output also serves as input for the hydrodynamic study.

The model needs no calibration. The model has been validated, including the role of groundwater, under the current situation on the (continuous) period 1993-1998 (for which detailed data are available). This period includes the five major flood events that recently occurred in the Geul basin. The conclusions obtained are that the hydrological model is able to simulate the hydrological behaviour of the watershed, including the groundwater transfers. Additional data must however be collected to assess precisely the possible losses of groundwater from the Gulp (and maybe from other tributaries) to the alluvial plain of the Meuse river.

As the hydrological model uses physically-based representations, it has been concluded that the model is able to simulate runoff and base flow for changes in land use or agricultural practices. The model has thus been used to simulate the different scenarios and to assess the effectiveness of the proposed land-related measures. The results show that the proposed environment-friendly measures do reduce the duration and fluxes of water to the river network under high rainfall events, but only weakly: the reduction is maximum 10%. In general, scenario 3 (transformation of farming and pastureland with slopes higher than 10% into forest) and land-related measures of scenario 4 (transformation of all farming land into farming land with green belts) show the highest improvements as regards daily water flux reduction. These scenarios give more or less the same result as the simulation of the historic land use scenarios of the 1950's. The simulated scenarios, especially the land-related measures of scenario 4 (farming land with green belts and hedgerows), are also favourable to decrease local erosion problems (gullies). This erosion problem would need some further (specific) elaboration.

 &RQFOXVLRQVRQWKHK\GURG\QDPLFVWXG\ The effectiveness of the scenarios on reducing the risk of flooding was studied in detail in the hydrodynamic study. The timing and location of the discharge (m³/sec) and the height (m) of the water flowing through the Geul river and its tributaries were simulated as a function of the water runoff calculated by the hydrological model. The ISIS Flow model is used as hydraulic simulation model. The results were plotted along a longitudinal profile of the Geul river, relative to the height of the riverbanks. Analysis permitted to conclude where the flood-prone areas are located and which scenario appears most favourable to reduce the risk of flash flood events.

Currently, major flooding problems occur upstream of the mills: Volmolen, Epermolen, Bovenste Molen, Wijlre, Oude Molen, Franse Molen and Groote Molen. Other flood- prone areas are the Geul river in Wallonia near the Dutch border, and the Geul river at the mouth with Eijserbeek and Gulp. The effectiveness of the land use measures, aimed to retain water in the uplands and to reduce the peaks of water runoff to the river

Conclusions 158 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas network, proved insufficient to prevent flooding. Peaks in river water discharge were maximally reduced by 10% for the historic land use scenario of the 1950's (as obtained in the hydrological study). Peaks in river water heights were maximally reduced by 22 cm. The installation of two constriction devices in the upstream parts of the Geul river, combined with land-related measures (all farming land with green belts or hedgerows), reduces the peak river water discharges by maximum 17%. This proved to be the only scenario with water heights in the Geul river generally below the heights of the riverbanks; however, it cannot guarantee the FRPSOHWH prevention of flooding problems.

This allows concluding that the flood problems in the Geul catchment are caused by a combination of climatic events, modifications of land use and agricultural practices, and managements operations in the riverbed (straightening, suppression of JUDIWHQ). Combining land-related measures with civil-technical measures in the river is thus necessary to reduce the risk of flash flood-related inundations along the Geul river.

 &RQFOXVLRQVRQWKHOHJDOIUDPHZRUN The legal framework and policy instruments at the disposal of local, provincial and national authorities in the three parts in the catchment were studied to assess their applicability for promoting and implementing the environmentally-sound measures studied here above. The instruments are multilateral and have been found in many sectors (water-resources management, land use planning, environmental planning, agricultural sector…). Important conclusions are that involvement and initiative of the policy-makers and stakeholders of all these sectors is of extreme importance, and trans- national cooperation is highly required.

Most of the proposed measures fit in the framework of at least one legislative tool and no major contradictions between proposed measures and existing legislation have been identified. This applies to both the Dutch, Flemish and Walloon part of the catchment. Crippling contradictions between legislations have not been found, although many differences in focus are present. No legislation provides a complete set of rules or a clear framework in which to place measures aimed at hydrological control on the river basin level. Measures do exist, but they are dispersed over a whole array of laws and regulations. More importantly, limiting the runoff is usually no primary goal; it is a secondary result of measures that are primarily intended to conserve biodiversity, to combat erosion or to optimise conditions for agriculture. It should also be noted that most relevant legislation does not have an area-based perspective. This is regrettable; as such a perspective could make it possible to use its tools in a spatially integrated way or to apply them selectively to watersheds one wants to protect. The only exception to this, almost by definition, are the land consolidation projects.

Conclusions 159 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

The legislations that seem to best sustain the proposed measures or at least have the potential to do so are both concerned with agriculture, not with nature or water conservation. Land consolidation projects for instance have an area approach and a scale that is ideally suited to implement many of the proposed measures. Although their primary goal is to optimise working conditions for agriculture, this does not exclude taking measures that favour water retention, and even provide the financial and technical means for doing so. The system of agro-ecological subsidies (following the European directive) is also an attractive instrument that allows for the implementation of a number of water retention measures proposed in the present study. Its effectiveness could be further enhanced by providing subsidies for measures specifically aiming at increasing water retention and by making it possible to differentiate the measures eligible for subsidies and even the amount of the subsidies on an area basis.

Sensitisation and awareness-raising to the need for water retention in the watershed appear to be of paramount importance for implementing most of the inventoried measures, since the most promising measures do depend on the goodwill of the land users. If measures are to be implemented and sustained in practice, a bottom-up approach towards the selection of measures, the location of the implementation of a measure etc. should be performed with all actors and stakeholders involved (participatory decision-making process). It is absolutely required to spend enough attention on the supply of information and sensitisation.

Finally, the applicability of many instruments is limited due to factors like limited financial resources and limited possibilities to expropriate privately owned land. Cooperation between sectors and authorities is not only required for effective use of the instrument, but also for further investigation and elaboration on the potencies of the instruments.

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The hydrological model proved to be effective to simulate the hydrological behaviour of the watershed, including groundwater transfers, despite some basic data (rainfall, discharges) being incomplete or questionable. Uncertainties however still remain, associated with possible losses of groundwater from some tributaries of the Geul towards the alluvial plain of the Meuse river. Nevertheless, the model results were accurate and the simulation results reacted sensitively to small changes in input, so that the effectiveness of the proposed land-related measures could be assessed. The hydrodynamic model calculated the discharge and the height of the water in the Geul river and its tributaries. The study located the flood-prone areas and investigated which scenario being favourable to reduce the risk of flash flood-related inundations.

Conclusions 160 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

The ‘cultivation’ of green belts and hedgerows in farming land provides an effective, but small, reduction of water fluxes to the river network under high rainfall events. The combination with the installation of constriction devices in the upstream riverbeds, proved effectively reducing peaks in river water height compared to the height of the riverbanks, and thus reducing the risk of flash flood-related inundations along the Geul river.

The introduction of green belts and hedgerows in agricultural parcels, although having in itself a relatively small effect on flash floods, is complementary useful to reduce the erosion from agricultural fields.

Conclusions 161 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

 5(&200(1'$7,216 An integrated approach towards water management at catchment scale is highly recommended to reduce the risk of flash flood events. Such a policy must be based on the results of a global analysis (hydrology, hydraulics) and has to tackle the causes, while ameliorating the water retention capacity of the watershed and the river. Efforts should be directed at making possible minor but effective changes to the existing legislation, and to better co-ordinate actions between responsible administrations.

The integrated approach should not only combine the points of view of different policy sectors (water-resources management, land use planning, environmental planning, agricultural sector…) and different levels in society (local, provincial and regional or national), but also take into account the trans-national concerns. For instance, policy- makers and land users in the upstream parts of a trans-boundary catchment should be aware and convinced of taking measures to reduce the risk on flash flood events, and the accompanying mudflow damage, in the downstream part of the catchment (e.g. consciousness on retaining water in the catchment by enhanced infiltration (pastureland or forest instead of bare fields, less paved surface, dispersion drain pipes instead of ordinary drain pipes…), or on slowing down the water flow instead of accelerating it (storage reservoirs, constriction devices)). A sustainable and sound land use planning should be established in order to prevent building on flood-prone areas or introducing infrastructure along watercourses. After all, flooding events have always existed in the Geul river region and high rainfall events will always remain. The increasing dissatisfaction especially results from the fact that more and more sediments are carried along by the river (increased erosion due to, among other things, maladjusted agricultural practices and land use in the hilly loess region), which are deposited in often improperly planned urban area during (flash) flood events. The importance and need of considering the water system as a guiding principle in land use planning is obvious. An elaborated and sound trans-boundary (European) legislative framework and regulations (incentives, taxes) should facilitate both the water retention and erosion combating in the Geul catchment. A re-valuation of the actual land use in the socio- economic context should also be considered (for instance promotion of other crops, promotion and subsidizing of biologic (small-scale) agriculture).

International cooperation is highly required. The Declaration of Arles, undersigned by the Ministers of Environment of France, Germany, Belgium, Luxembourg and The Netherlands, is a good starting point for the “new approach”. In this declaration, the Ministers officially declared that they deemed it necessary to reduce flood-related risks as rapidly as possible. Water retention should become one of the most important principles of water management. The policy- and instruments development regarding the current flood problems should be co-ordinated at catchment level.

Among the possible management measures, the transformation of farming land with slopes higher than 10% into forest and the introduction of green belts and hedgerows in

Recommendations 162 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas agricultural fields, in combination with the installation of constriction devices in the upstream riverbeds, are recommended, as they proved effectively reducing peaks in the river network under high rainfall events (while also reducing erosion from the agricultural fields).

Following the performed analysis and the obtained hydrological results, it is recommended: • to increase the availability and reliability of data (rainfall, river discharge, characterisation of urban areas); • to investigate by additional measurements and hydrogeological studies the question of possible direct losses of groundwater from the Geul catchment (especially from the tributaries of the Geul) towards the alluvial plain of the Meuse river. In the future, the problem of soil erosion in the Geul basin should be addressed as a problem in itself (and not just in relation to flood events). For future hydrological studies, it is recommended to pursue the utilization of the hydrological model MOHICAN, as it has proved to efficiently simulate the hydrological behaviour of the watershed, including groundwater transfers. Additional advantage is that this model simulates the topsoil dynamics and the crop growth.

Harmonizing GIS data and improving the availability of these data within Europe could significantly improve the quality and reliability of the results obtained in trans-boundary projects. It could also save a lot of time and money on comparable projects in the future. As part of this report, the GIS team suggests the following to local, national, and European Union officials: • A central European databank of unified meta-data should be created. • GIS data should be made more affordable in Europe. • Agreements concerning user rights and user restrictions should be made between government authorities to clarify the data exchange.

Recommendations 163 European Commission - DG Environment Walloon Regional Government Province of Limburg - The Netherlands Province of Limburg - Belgium Waterboard Roer & Overmaas

 5()(5(1&(6 The references to the literature used in this report are given in the Annexes.

References 164