Flood prone areas in The Netherlands

The table below shows the percentage of the Netherlands, its urban area and its population that is located in dike rings (embanked areas) and in flood-prone areas (river area + coastal zone; from (40)). Note that not all of the embanked areas are actually flood prone: there are higher grounds within the dike rings. Hence, 'only' about half of the urban area and population within these dike rings are in the flood-prone zone.

Dike rings Flood-prone zone Total area 55% 34% Total urban area 62% 31% Total population 67% 35%

The Netherlands: Vulnerabilities – flood probability trends in the past

As a consequence of increasing winter rainfall totals and intensities over the second half of the 20th century, signs of increased flooding probability in many areas of the Rhine and Meuse basins have been documented. These changes affecting rainfall characteristics are most evidently due to an increase in westerly atmospheric circulation types (26).

Land use changes, particularly urbanization, can have significant local effects in small basins (headwaters) with respect to flooding, especially during heavy local rainstorms, but no evidence exists that land use change has had significant effects on peak flows in the rivers Rhine and Meuse (26).

The Netherlands: Changes in flood damage in 20th century

During the 20th century the amount of urban area in the flood-prone part of the Dutch delta (river area + coastal zone) has increased about six-fold. This increase in urban area in the flood-prone zone has led to an exponential increase in potential flood damage during the 20th century: 16 times the damage of 1900 by 2000. However, GDP increased more than potential flood damage, and the capacity to deal with catastrophic flood losses has actually almost doubled in 2000 with respect to 1900 (40).

The Netherlands: Vulnerabilities - Non-climatic factors

Some studies report a (very) limited effect of changes in land use on the discharge regime for the main branches of the Meuse and Rhine rivers (26). Climate change has a much larger impact on discharges and droughts than extreme changes in land use (30).

Results of other studies, however, indicate that land-use change might affect flood risks at least as much as climate change (31). The size of future potential flood losses depends on the combination of scenarios for socioeconomic development (including land use change) and scenarios of climate change. For a polder area near the river Meuse both an optimistic and a pessimistic estimate has been made of potential flood losses by combining low scenarios of both socioeconomic development and climate change on the one hand, and high scenarios on the other. Thus the lower and upper ends of the impacts of population and economic growth on flood loss potentials have been explored. These estimates have been made for 2040 compared with 2000. Only direct physical flood damages to buildings and their contents, infrastructure, agriculture and nature have been addressed.

It was found that annual expected losses may increase by between 35 and 172% by the year 2040, due to socioeconomic change, including changes in asset value and land use, mostly consisting of expansion of urban areas. Without additional measures to reduce flood probabilities or consequences, climate change may lead to an increase in expected losses of between 46 and 201%. A combination of climate and socioeconomic change may push expected losses up by between 96 and 719%. This indicates that changes in climate may lead to disproportionate and therefore non-linear impacts (31).

These results are too dramatic, however, as flood risk policy is likely to take account of ongoing climate change and increasing exposure. In addition, local risk reduction measures can have drastic effects on flood losses (32).

At present about a third of all flood defences (including those of the coast, the rivers and the large lakes) do not comply with the current standards. For about half of these defenses improvements are being implemented; the improvements of the other half of the defences that failed the assessment still have to be planned (39).

The Netherlands: Potential flood damage in 2100

Future projections of socio-economic changes, based on scenarios for 2100 constructed in line with scenarios available for 2040 (41), show a further increase of urban area in the flood-prone zone in 2100 by +30% (scenario low economic growth) to 125% (scenario high economic growth) with respect to 2000 (river area + coastal zone) (40). It is projected that in both scenarios these developments take place in relatively unsafe locations with potential inundation depths often exceeding 2.5 m. These projections only refer to socio-economic changes: the impact of flood protection works and changing hydraulic conditions (due to e.g. climate change) are not included.

These projections indicate that potential damages will continue to increase during the 21st century, two- to three-fold and tenfold by 2100, for the scenarios of low and high economic growth respectively. The capacity to cope with these increased flood damages, due to changes in GDP, probably will not change much (40).

The Netherlands: Vulnerabilities – future flood probability Rhine

Recently, a thorough study has been carried out into the change of the discharge of the River Rhine during the 21st century. It was concluded that average discharge during summer and winter half-year will increase in 2021-2050 with respect to 1961-1990. At the end of the century (2071-2100) average half-year discharge is projected to increase in the winter and decrease in the summer. High winter discharge is projected to increase both in 2021-2050 and 2071-2100 with respect to 1961-1990 (21).

The 1/100-years discharge of the Rhine near the Dutch-German border is projected to increase by 0-20% in 2021-2050 and by 0-25% in 2071-2100. A similar relative increase is projected for the 1/1000-years discharge (21).

The impact of climate and land use changes on Rhine high and low river discharge was studied (30). Two scenarios were used: a moderate (G+) and warm (W+) scenario of 1 and 2°C temperature rise in 2050, respectively, compared with 1990, and in both scenarios milder and wetter winters, and warmer and drier summers due to changes in air circulation patterns in Western Europe.

From this study it was projected that the discharge of the Rhine at Lobith (the Dutch-German border) will decrease on average by 5% (G+) to 8% (W+) in 2050. Both droughts and floods will be more intense. Maximum discharges at Lobith will be higher: mean annual maximum discharge at Lobith is projected to increase by 2% (G+) to 6% (W+) (30).

In the Netherlands a so-called Delta committee wrote a report on possible (worst case) climate change, sea level rise and river discharge changes in the 21st century. Based on this report an adaptation strategy is being implemented to climate proof the country. The Delta Committee projected an increase of peak Rhine discharge probability like the one of 1995 from 2%/year at present to 10%/year in 2100. Besides, the Committee projected that the discharge capacity of the Dutch Rhine may need to be increased from 16.000 m3/s at present to 17.000 – 22.000 m3/s in 2100 (22).

At present, however, there is a limited discharge capacity for the Rhine in Germany. This means that, when the circumstances in the German river area do not change (no further raising of dikes, for instance), the maximum Rhine discharge in the Netherlands is 18,000 m3/s (23).

The Rhine compared with other large rivers

Climate change will affect high and low flow volumes of large rivers around the globe. To what extent extreme flows will change differs from one region to another. These changes have been assessed for five large rivers from three continents (48). Two in Europe: the Rhine River (at the Lobith station in the Netherlands) and the Tagus in Portugal (at Almourol), one in Africa (Niger at Lokoja), and two in Asia (Ganges at Farakka and Lena at Stolb). The assessment was made for the near future (period 2006-2035), mid-century (2036-2065), and end-century (2070-2099), compared with the reference period 1981-2010. A total of 20 climate projections was made: five climate models (GCMs) linked to five hydrological models times four different scenarios of climate change ranging from a low- to a high-end scenario of global warming (the so-called RCPs 2.6, 4.5, 6.0 and 8.5).

In this study high and extremely high flows were defined as the 10 % and 1 % highest discharges of all discharges in a certain period (the so-called Q10 and Q01). Likewise, low flows were defined as the 10 % lowest discharges (Q90). The Rhine shows the smallest expected changes in high flows (compared with the other rivers) (between ±15 %) in all climate change scenarios and future periods, and a reduction of low flows up to −50 % in 2100. Similar trends were shown for the Rhine in other studies on high flows (49,51,52) and low flows (50,51,52). 

The Netherlands: Vulnerabilities – future flood probability Meuse

Similar to the expectation for the Rhine, the winter discharge of the Meuse will also be higher in the future than it is at present. The Delta Committee projected that the discharge capacity of the Meuse may need to be increased from 3.800 m3/s at present to 4.600 m3/s in 2100 (22).

Europe: casualties in the past

The annual number of reported flood disasters in Europe increased considerably in 1973-2002 (1). A disaster was defined here as causing the death of at least ten people, or affecting seriously at least 100 people, or requiring immediate emergency assistance. The total number of reported victims was 2626 during the whole period, the most deadly floods occurred in Spain in 1973 (272 victims), in Italy in 1998 (147 victims) and in Russia in 1993 (125 victims) (2).

Throughout the 20th century as a whole flood-related deaths have been either stable or decreasing while economic burdens of flooding and related societal disruptions have become decidedly worse. 20th century flood disaster death tolls have been typically averaging fewer than 250 per year (3).

Europe: flood losses in the past

The reported damages also increased. Three countries had damages in excess of €10 billion (Italy, Spain, Germany), three in excess of 5 billion (United Kingdom, Poland, France) (2).

Expressed in 2006 US$ normalised values, total flood losses over the 1970–2006 period amounted to 140 billion, with an average annual flood loss of 3.8 billion (4). Results show no detectable sign of human-induced climate change in normalised flood losses in Europe. There is evidence that societal change and economic development are the principal factors responsible for the increasing losses from natural disasters to date (5).

Policy makers should not expect an unequivocal answer to questions concerning the linkage between flood-disaster losses and anthropogenic climate change, as this field will very likely remain an important area of research for years to come. Longer time-series of losses are necessary for more conclusive results (6).

Europe: flood frequency trends in the past

In 2012 the IPCC concluded that there is limited to medium evidence available to assess climate-driven observed changes in the magnitude and frequency of floods at a regional scale because the available instrumental records of floods at gauge stations are limited in space and time, and because of confounding effects of changes in land use and engineering. Furthermore, there is low agreement in this evidence, and thus overall low confidence at the global scale regarding even the sign of these changes. There is low confidence (due to limited evidence) that anthropogenic climate change has affected the magnitude or frequency of floods, though it has detectably influenced several components of the hydrological cycle such as precipitation and snowmelt (medium confidence to high confidence), which may impact flood trends (37).

Despite the considerable rise in the number of reported major flood events and economic losses caused by floods in Europe over recent decades, no significant general climate‑related trend in extreme high river flows that induce floods has yet been detected (7).

Hydrological data series do not indicate clear upward trends in the frequency and magnitude of floods in Europe. The direct anthropogenic causes include land use change, river channel modifications and increased activities in areas vulnerable to floods. Thousands of square kilometres of impermeable surfaces have been created, coastal urbanization has been extensive. The overall impact of these changes probably exceeds the impact of trends in meteorological variables in today's Europe (8).

In western and central Europe, annual and monthly mean river flow series appear to have been stationary over the 20th century (9). In mountainous regions of central Europe, however, the main identified trends are an increase in annual river flow due to increases in winter, spring and autumn river flow. In southern parts of Europe, a slightly decreasing trend in annual river flow has been observed (10).

In the Nordic countries, snowmelt floods have occurred earlier because of warmer winters (11). In Portugal, changed precipitation patterns have resulted in larger and more frequent floods during autumn but a decline in the number of floods in winter and spring (12). Comparisons of historic climate variability with flood records suggest, however, that many of the changes observed in recent decades could have resulted from natural climatic variation. Changes in the terrestrial system, such as urbanisation, deforestation, loss of natural floodplain storage, as well as river and flood management have also strongly affected flood occurrence (13).

Europe: projections for the future

IPCC conclusions

In 2012 the IPCC concluded that considerable uncertainty remains in the projections of flood changes, especially regarding their magnitude and frequency. They concluded, therefore, that there is low confidence (due to limited evidence) in future changes in flood magnitude and frequency derived from river discharge simulations. Projected precipitation and temperature changes imply possible changes in floods, although overall there is low confidence in projections of changes in fluvial floods. Confidence is low due to limited evidence and because the causes of regional changes are complex, although there are exceptions to this statement. There is medium confidence (based on physical reasoning) that projected increases in heavy rainfall would contribute to increases in rain-generated local flooding, in some catchments or regions. Earlier spring peak flows in snowmelt- and glacier-fed rivers are very likely, but there is low confidence in their projected magnitude (37).

More frequent flash floods

Although there is as yet no proof that the extreme flood events of recent years are a direct consequence of climate change, they may give an indication of what can be expected: the frequency and intensity of floods in large parts of Europe is projected to increase (14). In particular, flash and urban floods, triggered by local intense precipitation events, are likely to be more frequent throughout Europe (15).

More frequent floods in the winter

Flood hazard will also probably increase during wetter and warmer winters, with more frequent rain and less frequent snow (16). Even in regions where mean river flows will drop significantly, as in the Iberian Peninsula, the projected increase in precipitation intensity and variability may cause more floods.

Reduction spring snowmelt floods

In snow‑dominated regions such as the Alps, the Carpathian Mountains and northern parts of Europe, spring snowmelt floods are projected to decrease due to a shorter snow season and less snow accumulation in warmer winters (17). Earlier snowmelt and reduced summer precipitation will reduce river flows in summer (18), when demand is typically highest.

For the period 2071-2100 the general feature is a decrease of extreme flows in areas where snowmelt floods are dominating in the present climate. The hundred year floods will attenuate by 10-50% in northern Russia, Finland and most mountainous catchments throughout Europe. An increase by similar amount is projected in large areas elsewhere, whereas a mixed pattern is likely in Sweden, Germany and the Iberian Peninsula (2).

Large differences across Europe

Annual river flow is projected to decrease in southern and south-eastern Europe and increase in northern and north-eastern Europe (19).

Strong changes are also projected in the seasonality of river flows, with large differences across Europe. Winter and spring river flows are projected to increase in most parts of Europe, except for the most southern and south-eastern regions. In summer and autumn, river flows are projected to decrease in most of Europe, except for northern and north-eastern regions where autumn flows are projected to increase (20). Predicted reductions in summer flow are greatest for southern and south-eastern Europe, in line with the predicted increase in the frequency and severity of drought in this region.

Climate-related changes in flood frequency are complex and dependent on the flood generating mechanism (e.g. heavy rainfall vs spring snowmelt), affected in different ways by climate change. Hence, in the regions where floods can be caused by several possible mechanisms, the net effect of climate change on flood risk is not trivial and a general and ubiquitously valid, flat-rate statement on change in flood risk cannot be made (29).

Flood risk tends to increase over many areas owing to a range of climatic and non-climatic impacts, whose relative importance is site-specific. Flood risk is controlled by a number of non-climatic factors, such as changes in economic and social systems, and in terrestrial systems (hydrological systems and ecosystems). Land-use changes, which induce land-cover changes, control the rainfall-runoff relations in the drainage basin. Deforestation, urbanization and reduction of wetlands diminish the available water-storage capacity and increase the runoff coefficient, leading to growth in the flow amplitude and reduction of the time-to-peak. Furthermore, in many regions, people have been encroaching into, and developing, flood-prone areas, thereby increasing the damage potential. Important factors of relevance to flood risk are population and economy growth, flood protection strategy, flood risk awareness (or flood risk ignorance) behaviour and a compensation culture (29).

Increase flood losses

Losses from river flood disasters in Europe have worsened in recent years and climate change is expected to exacerbate this trend. The PESETA study, for example, estimates that by the 2080s, some 250-400 million Europeans could be affected each year (compared with 200 million in the period between 1961 and 1990). At the same time, annual losses due to river flooding in Europe could rise to €8-15 billion by the end of the century compared with an average of €6 billion today (28).

From an assessment of the implications of climate change for future flood damage and people exposed by floods in Europe it was concluded that the expected annual damages (EAD) and expected annual population exposed (EAP) will see an increase in several countries in Europe in the coming century (38). Most notable increases in flood losses across the different climate futures are projected for countries in Western Europe (Belgium, Denmark, France, Germany, Ireland, Luxembourg, the Netherlands and the United Kingdom), as well as for Hungary and Slovakia. A consistent decrease across the scenarios is projected for northern countries (Estonia, Finland, Latvia, Lithuania and Sweden). For EU27 as a whole, current EAD of approximately €6.4 billion is projected to at least double or triple by the end of this century (in today’s prices), depending on the scenario. Changes in EAP reflect well the changes in EAD, and for EU27 an additional 250,000 to nearly 400,000 people are expected to be affected by flooding yearly, depending on the scenario. The authors stress that the monetary estimates of flood damage are uncertain because of several assumptions underlying the calculations (only two emission scenarios, only two regional climate models driven by two general circulation models, no discounting of inflation to future damages, no growth in exposed values and population or adjustments, estimates of flood protection standards); the results are indicative of changes in flood damage due to climate change, however, rather than estimates of absolute values of flood damage (38).

Adaptation strategies - Overall National Policy outline

Climate change and adaptation measures are strongly integrated into the water policy agenda. It has been recognised that, in the coming years, technical measures, such as raising dykes, will no longer be sufficient to compensate for increasing water levels in the rivers and the accelerated sea level rise (23).

With the Water Outlook (Watervisie) in 2007, the Dutch government set out the aim of stepping up its ambitions and pursuing sustainable and climate proof water management (27). To achieve this aim, the Cabinet established the second Delta Committee to advise on water policy for the next century and beyond. In 2008, the Delta Committee proposed increasing flood protection and securing freshwater supplies in the long term (22).

The first policy-based detailing of this vision now forms part of the National Water Plan. A Delta Bill (Deltawet) guarantees the continuity and cohesion of this approach in the long term as well (23).

The central government’s ambition is to invest in flood protection and defence to allow more space for water, in working together to implement water policy, „go with the flow‟and to enhance the role of water adaptation and spatial planning. Safety continues to be the top priority. Other goals are to avoid destruction of the considerable cultural-historical and natural value of the river landscapes. Guiding principles are (23):

• anticipating instead of reacting;
• following a three-step strategy (first retention, then storage and, as a last resort, drainage);
• allocating more space for water (e.g. assigning emergency flood areas) in addition to implementing technological measures (e.g. dyke reinforcement);
• raise beach levels.

Adaptation strategies - The Delta Committee

Based on the report of the Dutch Delta Committee an adaptation strategy is being implemented to climate proof the country in the 21st century (22). In the Delta Committee’s view, assessment of the safety level of various dyked areas must be based on three elements:

1. the probability of fatalities due to flooding;
2. the probability of large numbers of casualties in a single flood episode;
3. possible damage, involving more than economic harm alone.

It is the Committee’s view that damage to the landscape, nature and cultural heritage assets, societal disruption and a harmed reputation must be explicitly incorporated. In combination, these three elements result in a single, amended standard for water safety. The Committee assumes the level of flood protection must be raised by at least a factor of 10 with respect to the present level.

Adaptation strategies – national level

Several measures have been carried out to increase the discharge capacity of the rivers Rhine and Meuse (Room for the River (Ruimte voor de Rivier), and the Meuse projects (Maaswerken)). Common measures are retention areas, river widening and bypasses. These measures preferably serve both water issues and other space-demanding issues (housing, leisure, biodiversity, farming etc.) (23,53).These measures are meant to increase the discharge capacity such that the current safety levels are met; they do not anticipate the possible future concequences of climate change. Discharge capacity for the Rhine should be large enough to handle a peak discharge level of 16,000 m3/s and the Meuse a discharge level of 3,800 m3/s. To anticipate higher peak discharges (climate change) in the 21st century, land should be set aside and where necessary, purchased, outside (and possibly also inside) the dykes allowing for future measures to eventually further increase the discharge capacity to 18,000 m3/s for the Rhine and 4,600 m3/s for the Meuse (23).

Delta Programme

In the Netherlands a Delta Programme has been initiated aimed at, among others, improving the flood defence system. The Delta Programme focuses on three main topics: flood safety, fresh water security, and new urban development and restructuring (36).

The Delta Programme discriminates between 6 regions, each having their own vulnerabilities with respect to climate change, and thus asking for tailor-made adaptation measures:

1. Rhine estuary – Drechtsteden: flood protection of the Rhine – Meuse - Delta
2. Southwestern Delta: climate change impacts on flood safety, fresh water availability, nature and regional economic development from 2050 onwards
3. IJsselmeer Region: long-term water level management for flood safety (free discharge of lake water on the Wadden Sea under sea level rise) and fresh water security (a larger reservoir for dry summers)
4. Rivers: implementation measures for increasing discharge capacity Rhine and Meuse (short-term); securing flood safety along with addressing fresh water supply, shipping, nature and regional development (long-term)
5. The Coast: focus on a sustainable flood protection strategy and options for coastal expansion
6. Wadden Region: focus on several issues, a.o. integrated coastal and island management, innovation in dike construction, sediment budgets, and climate proofing areas outside the dikes

In 2015 the Delta Programme will result in five Delta Decisions for flood safety and securing fresh water reserves for 2050 with an outlook towards 2100. Proposals for the following Delta Decisions are foreseen (36):

1. Delta Decision Flood risk management. Updating flood protection standards and development of area-based strategies for flood protection The area-based strategies provide insights into promising combinations of measures (delta) dykes, river-widening and/or spatial development measures including natural safety measures (“Building with nature”), adaptive construction and organization], insights into financial requirements, chances for spatial adjustment, social base, planning and feasibility of implementation.
2. Delta Decision Freshwater strategy.
3. Delta Decision Spatial adaptation. National policy framework new urban developments and restructuring and recommendations around flooding and heat stress. The proposal for this Delta Decision yields a strategy on means and conditions for robust development in built-up areas in the Netherlands. The policy will at least cover the topics of the built-up area in- and outside the dykes as well as in, on and around water defence systems and reserved areas from the angle of flood risk management and pluvial flooding.
4. Delta Decision Rhine-Meuse delta. Strategy for flood protection in this crucial transitional delta area, together with solutions for freshwater supplies. The Rhine-Meuse delta is the location of the major rivers, Rhine Estuary-Drechtsteden and the southwest delta. This is a key transitional area in the Dutch delta. River and sea come together here, and there is a wide range of interests requiring protection – both in terms of population and economic activity. The proposal for the Delta Decision comprises one or more strategies to ensure flood protection and sustainable freshwater supplies up to 2050 followed by a forward view to 2100.
5. Delta Decision Water level management Ijsselmeer Region.

More information on these Delta Decisions and the steps to be made in the period 2012 -2015 is presented in the Coastal Floods theme.

Strategic options for climate-proofing the Netherlands

Strategic options for a climate-proof development of the Netherlands are building unbreachable dykes and managing new development in the Rhine-Meuse floodplain (33).

Unbreachable dykes (so-called Delta Dykes) are an effective way to reduce the possible consequences of flooding, especially in areas with the highest concentrations of population and fixed assets (34). The construction of unbreachable dykes will sharply reduce the risk of damages and casualties because, although these dykes can be overtopped, much less water will flow into an area – considerably reducing the speed at which such an area becomes flooded as well as reducing the depth of the flood waters. Thus, the consequences of flooding would remain limited to such an extent that there is little need for adjustment to built-up areas behind these dykes in order to reduce the consequences of flooding (flood-resilient building). The number of fatalities is believed to drop by one or two orders of magnitude. A 50% fatality risk reduction is to be expected when applying Delta Dykes along only 200 kilometres of the 3500 kilometres of flood defences in the Netherlands (33).

The additional costs of making dykes unbreachable can be limited if these works can be incorporated into the restructuring of urban areas along rivers and the coast (multifunctional dykes), or combined with the implementation of the Flood Protection Programme, bringing all flood defences up to standard (33).

In addition, areas must be reserved in the Rhine-Meuse floodplain for managing the consequences of potentially higher river discharges in the future, combined with higher sea levels, in the longer term. This will require management of new spatial developments in the riverine areas. The measures taken in the present Room for the River programme will then no longer be adequate (35). Maintaining these open areas in the Rhine-Meuse floodplain does not mean that these areas cannot be used: buildings can de designed to minimise their vulnerability to flooding; for example, by building on raised areas or on stilts, and farming can also continue and recreational areas be developed, possibly linked to the conservation and restoration of internationally important riverine habitats and river landscapes (33).

Adaptation strategies – local level

At the municipalities level, water plans include measures to increase green spaces and water in city developments, thus making urban areas more attractive and liveable. This contributes to climate-proofing the urban environment. Measures also focus on separating the run-off from rainfall and sewerage. They include increased infiltration of precipitation, retaining groundwater at levels beneficial to the ecosystem and increased capacity to remove excess water. Municipalities are legally required to compensate for lost infiltration capacity. A water assessment is a standard procedure at the implementation of large projects (23).

For the regional water systems, provinces, municipalities and water boards have made an analysis of the problems in the so-called sub catchment visions and have assessed the spatial measures necessary to prevent floods. Most of the sub catchment visions have adopted the standard that ‘light floods’ is based on the present design standard for discharge capacity; i.e. rainfall which occurs once every 100 years. For rural areas the agreed-upon working standards are substantially lower. Generally enough capacity exists within the current water systems to deal with even light floods (24).

Adaptation measures with respect to water management in the built environment include ‘floating houses and industrial buildings’. To date this type of floating housing and infrastructure has hardly been applied, except for some permanent and some recreational houses, hence incremental costs and benefits associated with this type of spatial design are not available yet, and they will strongly depend on local circumstances (25).

Flood risk reduction via​ private damage-reducing measures

Two types of building precautionary measures aim at minimising damage (45):

• wet flood proofing: flood-adapted use and equipment of buildings. Examples of wet flood proofing are the following: to adapt the building use, which means that cellars and endangered floors are not used cost intensively; to adapt the interior fitting which means that in endangered floors only waterproofed building material and movable small interior decoration and furniture are used; or to safeguard possible sources of contamination, such as an oil tank of a heating system.
• dry flood proofing: sealing, reinforcement and shielding. Examples of dry flood proofing measures are: adapting the building structure via an elevated configuration; to waterproof seal the cellar, e.g. by constructing the basis and walls of buildings out of concrete that is non-permeable; or to deploy mobile flood barriers such as temporary flood guards.

The deployment of wet proofing, dry proofing and elevating buildings for an unembanked area in Rotterdam could completely offset the projected increase in flood risk caused by climate change, which is expected to double by 2100 if no adaptation measures are undertaken (46). According to another study a risk-reduction of 60 % can be achieved for the Meuse basin for non-structural measures at the building level in combination with spatial planning policies (47).  

Adaptation strategies - EU Directive on flood risk management

The new EU Directive on flood risk management, which entered into force in November 2006, introduces new instruments to manage risks from flooding, and is thus highly relevant in the context of adaptation to climate change impacts. The Directive introduces a three-step approach (2):

• Member States have to undertake a preliminary assessment of flood risk in river basins and coastal zones.
• Where significant risk is identified, flood hazard maps and flood risk maps have to be developed.
• Flood risk management plans must be developed for these zones. These plans have to include measures that will reduce the potential adverse consequences of flooding for human health, the environment cultural heritage and economic activity, and they should focus on prevention, protection and preparedness.

Adaptation strategies - Exploring pathways for sustainable water management

Adaptation tipping points have been defined as points where the magnitude of change due to climate change or sea level rise is such that the current water management strategy will no longer be able to meet the objectives and alternative strategies are needed. The driver for taking action is not climate change, but being unable to meet objectives. Thus climate change is only one of the issues. Socio-economic developments, for instance, may also result in (earlier) adaptation tipping points. Once an adaptation tipping point is in sight, a switch to a new strategy is needed. Each new strategy has its own future tipping point that, again, requires a switch to be made. In the long run water management is thus a succession of strategies. Several successions are possible (42).

The successions of strategies into the future are adaptation pathways in a changing environment. These  pathways can be explored from many possible transient scenarios of climate and socio-economic developments. This approach shows the range of options from which policy makers can choose. The adaptation pathways approach thus supports decision making for sustainable water management in a changing environment (43).

Sustainable water management is about making the best choices at the right moments for a long period of time. These choices will be influenced by events, such as floods and droughts, and changing societal perspectives on preferred strategies, as well as by new insights and knowledge in the course of time. Adaptation thus follows pathways of strategies that are influenced by current and future climate, socio-economic developments and societal perspectives. A strategy is sustainable when it can cope with various possible futures while being flexible enough to be adapted in case the future unfolds differently than anticipated (43).

A new method explores the range of possible adaptation pathways by simulating the dynamics of these pathways in response to the variability and change of climate and socio-economic factors for the next say 100 years. A model is used that represents realistic cause-effect relations between climate change and socio-economic pressures and their impacts on the water system and society. In each run of the model, a  year-by-year set of calculations is made in which a climate realization with, for instance, corresponding precipitation results in a peak river discharge and associated impacts. Management measures may then be taken accordingly, either defined a-priori or derived from policy makers in a workshop settingthrough a multi-actor, interactive game (43).

The pathways give information on the effectiveness and timing of measures. They also show dead-ends or the options left when a specific decision is made. The method includes both natural and social uncertainties, and thus allows for finding both physically and socially robust pathways. The model that is used allows for a rapid assessment of many transient scenarios to explore many futures and responses to these futures. It appears, for instance, that climate variability may be at least as important for decision making as climate change, especially for the mid to long term (43).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for the Netherlands.

1. Hoyois and Guha-Sapir (2003), In: Anderson (ed.) (2007)
2. Anderson (ed.) (2007)
3. Mitchell (2003)
4. Barredo (2009)
5. Höppe and Pielke Jr. (2006); Schiermeier (2006), both in: Barredo (2009)
6. Höppe and Pielke Jr. (2006), in: Barredo (2009)
7. Becker and Grunewald (2003); Glaser and Stangl (2003); Mudelsee et al.(2003); Kundzewicz et al.(2005); Pinter et al.(2006); Hisdal et al.(2007); Macklin and Rumsby (2007), all in: EEA, JRC and WHO (2008)
8. EEA, JRC and WHO (2008)
9. Wang et al.(2005), in: EEA, JRC and WHO (2008)
10. Milly et al. (2005), in: EEA, JRC and WHO (2008)
11. Hisdal et al. (2007), in: EEA, JRC and WHO (2008)
12. Ramos and Reis (2002), in: EEA, JRC and WHO (2008)
13. Barnolas and Llasat (2007), in: EEA, JRC and WHO (2008)
14. Lehner et al.(2006); Dankers and Feyen (2008b), both in: EEA, JRC and WHO (2008)
15. Christensen and Christensen (2003); Kundzewicz et al.(2006), both in: EEA, JRC and WHO (2008)
16. Palmer and Räisänen (2002), in: EEA, JRC and WHO (2008)
17. Kay et al. (2006); Dankers and Feyen (2008), in: EEA, JRC and WHO (2008)
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