Chapter 4

Water Management

Abstract River discharges will perform increasingly variable in the future. The question in the summer will be if there is enough water in the river to stay suitable for passing ships while in the winter period the question is if the riverbed is broad enough to discharge all the water without flooding neighbouring areas. Especially the discharge in wintertime causes major problems and floods. The way this problem is tackled ca be divided in two approaches: there are ways to prevent floods and there are ways to deal with the effects of a flood.

Beside the protection by making regulations on what is aloud and what is not aloud in or near the riverbed, another way to prevent the river from flooding is to create stronger defences, like dikes. The other approach is to move with the dynamic of the river. The river dynamics are offered more space in order to mitigate the most extreme dynamic. Around the river basins and ecological zones can be created to prevent large amounts of rainwater to enter the river immediately. Finally all kinds

Reviewed by Bryan Boult, Hampshire County Council, United Kingdom

R. Roggema, Adaptation to Climate Change: A Spatial Challenge, 183

DOI 10.1007/978-1-4020-9359-3_4, © Springer Science+Business Media B.V. 2009

of adjustments can be made at buildings. The houses can be closed in times of flooding or floating houses can be developed. The needed adjustments are different depending on the location of the house: standing in a deep polder close to the river is more dangerous and requires heavier measures than a location in shallow places further from the river.

The risk at a flood can be determined from the chance point of view or from a possible damage point of view. Both ways can be used to decrease the risk. Protection is as important as the mitigation of the effects of a flood.

If the flexibility in and around rivers is increased there is a better chance that floods can be prevented and the impacts of huge river discharges can be minimised. If the river is tamed with strong and fierce structures eventually an unexpected or uncalculated rise in water levels leads to a surprising flood.

4.1 Water Policies in The Netherlands 4.1.1 Risk

The Netherlands lives at the edge of land and water. This means that certain risks at floods and annoyance is always apparent in the country. Due to climate change this risk is increased, for instance by a rising sea level or by an increasing amount and intensity of precipitation. The risk increases also if the value of an area under threat is higher, for instance if more people inhabit the area or the potential economical damage is high. In general the formula risk = chance x effect indicates the level of risk for an area. The risk for a certain area equals the chance at a flood (protection level) times the effect of the flood (damage and casualties). This is the reason why dike-rings in the Netherlands have different protection levels (Fig. 4.1). If a flood has lower effect, the protection level can be lower as well, while the risk level stays at the same level, compared with an area where the effect is higher but the protection level also. By the way, the counted value within a dike-ring is not always in harmony with the real level (as compared in Figs. 4.1 and 4.2). The comparison shows that the Northern part of the Netherlands a relatively high economical value, while the protection level is beneath the level of the Randstad Holland. It seems that the protection level of the North is underestimated or the level in the Randstad overvalued. The question is to what extend the risk spiral upwards can be followed. A heightened safety feeling leads to the increase of investments, which require higher dikes, which increase the feeling of safety, which leads to more investments and so on [Rijcken, 2007]. While at the same time, a dike breech of heightened dikes lead to big disaster. This would pledge for a spread out defence against floods with once in a while a controlled flood that lead to minimal and predictable damage. In this way of thinking, the adjustment of the spatial lay out to the effects of flooding gains importance. Both approaches - heightening the dikes to minimise flood risks and dealing with the consequences of controlled flooding - are necessary.

Fig. 4.1 Safety level by dikering (Source: Ministerie van V&W)

4.1.2 Water Policy in the 21st Century

The problems in water systems are caused by the technical way the water was treated [Commissie Waterbeheer 21ste eeuw, 2000]. The natural resilience of the water system has decreased because floods needed to be prevented, navigation needed to be provided with enough depth in waterways, the agriculture needs to be provided with enough fresh water, the energy plants with enough cool water, marshy polders

needed to be reclaimed in order to make it suitable for housing and as much land as possible was reclaimed, because water was worthless (Ministerie van Verkeer en Waterstaat, 2007). Due to climate change the pressure on the water system increases. Larger amounts of precipitation need to be discharged in shorter periods, while sea level rise makes it increasingly difficult to discharge the water in a natural way. Therefore, it is necessary to increase the resilience of the water system again. Natural processes need to be recovered and the water system needs to get the space to function. The advice of the commission water management in the 21st century several proposals were done already. The problems of climate change and sea level rise were taken seriously and the conclusion was that the current water system was not very good prepared on the future. A three-steps-strategy was suggested: Start with retaining as much water as possible, secondly store water and finally - if no other option is left - discharge it. The objective of this strategy was to prevent the roll off of problems towards other areas or people. The water system needed to be adjusted to reach this goal. Extra room for rivers was required, areas needed to be realised as storage basins, a higher and broader coastal defence needed to be realised and the water policies needed to be detailed at a regional level. If these measures were taken, water was able to play a steering role in spatial planning by creating more space for water or to realise multifunctional land use (Commissie Waterbeheer 21ste eeuw, 2000).

4.1.3 Dutch National Water Vision

The adjustment of the water system is undertaken even more thoroughly in the national water vision. The aim is to have a national water plan ready by the year 2009, in which a sustainable and integrated climate proof water management for the entire country is laid out. The national water plan contains a target image for the long-term is connected with a spatial structure vision for the Netherlands, in which the spatial consequences are laid down as well as a working program for the first six years is formulated (Ministerie van Verkeer en Waterstaat, 2007). In the water vision five steering points are defined:

The first one is a climate proof Netherlands. The adaptation of the water system to climate change in the lower parts of the Netherlands needs to be realised in a way that all build up capital behind the dikes is not given away to the sea. Beside the adjustments of the coastal defence (see Chapter 3), adjustments in the spatial lay out and the way buildings are build will be necessary. Space is required to store water or to make storage in the future not impossible. Moreover, natural processes of the future need to play a steering role today in the development of spatial lay out of urban development, industry, nature, landscape and recreation. Furthermore, the vulnerability of the Netherlands can be minimised if investments are done in a climate proof way. The starting points for a climate proof lay out and a decision-making framework for the choice of locations, lay out of areas and the design of infrastructure and buildings will be put together (see also Adaptation agenda, Chapter 1).

4.1.4 Water Safety

Water safety aims to minimise the chances at a flood, but also to minimise the effects in case a flood happens, for instance by the creation of compartments within dike-rings, by building water proof or by keeping vital infrastructure usable during a flood.

The rivers in the Netherlands will have to deal in the future with an increasing amount of water that needs to be discharged. The discharge capacity of the big rivers in the Netherlands needs to be increased. The program Room for the River aims to realise this increase (Fig. 4.3). The rivers are given more room, for example by realisation of new high-tide channels. Other measures include the removal of obstacles, lowering the outer marches, lowering river jetties, reposition dikes, depolder, deepening the summer-bed or strengthening the dikes. If new high tide channels or changing the riverbeds offer chances at the realisation of attractive living environments (Fig. 4.4) and offers the river more space at the same time. Moreover, extra nature and recreation can be realised.

Fig. 4.4 Building water proof in the riverbed (Source, Ministerie van V&W, 2006b)

Fig. 4.3 Overview over the Room for the River measures (Source: Ministerie van V&W, 2006a)

Fig. 4.4 Building water proof in the riverbed (Source, Ministerie van V&W, 2006b)

Fig. 4.3 Overview over the Room for the River measures (Source: Ministerie van V&W, 2006a)

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