Climate change leads towards changes in the future precipitation pattern. In Belgium summers are getting dryer and winters wetter. The precipitation quantity of an extreme rain shower, as happens once a year, will increase with 24% towards 2100 under the high impact scenario of climate change, the precipitation quantity of an extreme rain shower, as happens once every 20 years, will increase with 45%. These trends will have their impact on flooding, from rains and rivers. The changes in precipitation pattern affect the water system together with the increase of paved surfaces and water management projects on rivers. Peak flows and the chance of flooding have increased. These causes already damage more than once every 10 years in some areas.
Extreme precipitation leads to floods with economic and ecological consequences, as well as psychological impact and damage to the cultural heritage. Pluvial or fluvial flooding caused a lot of damage in the whole country in the past few years. A further increase of damage by flooding is to be expected. The strong increase of extreme short rain showers will burden sewerage systems and other drainage systems. These sewerage systems do not only drain wastewater but also rainwater. The heavy precipitation causes increase of peak flows in sewerage systems, streams and ditches. The extreme showers will lead to a gradually increase of sewer flooding and overflow in the next decennia. This affects the design and dimensions of the infrastructure. Flooding can also affect transport infrastructure and energy producing infrastructure, and buildings in general. As well as in agriculture where they can lead to severe consequences by erosion of fertile soils.
Flanders is extremely vulnerable for water scarcity. Within Europe, Flanders is one of the regions with the lowest amount of water available per citizen due to a combination of the population density and a relatively low amount of surface and ground water. Climate scenario’ s predicts a decrease of rains in summer and an increase of evaporation.
Long-lasting drought can affect crops and limit their growth. The drink water supply can be compromised. Long lasting drought can cause problems with the navigability of watercourses which compromises the inland shipping. But also, other sectors with water as an important element of the production process can be affected by drought. Drought can also lead to a reduced water quality.
Drought has an impact on forests and nature which might lead to a loss of biodiversity and ecosystem services on the long term. Drought in combination with heath increases the risk of forest and nature fires, which leads to losses of biodiversity, decrease of carbon stock in biomass and additional emissions of CO2. It can also be a thread for agricultural areas, air quality and health.
In Flanders the principles of multi-layer water security are applied to reduce the risk on damage caused by flooding. This includes protection against critical flooding as well as prevention of damage and prediction and warning for flooding (preparedness). To reduce the risks of flooding is a shared responsibility of governments, sectors and citizens. The policy on flooding in Flanders is the execution of the directive on flooding (a better prediction of flooding and measures to control the damage). http://www.integraalwaterbeleid.be/en
In the next decennia Flanders will continue to work on prevention of damage by flooding. Even without increased damage by climate change, the economic and population growth will cause more damage by flooding in certain areas. In densely populated Flanders space for water systems is limited which complicates, together with an excess of sediment, the unstable balance of the water systems. Most climate scenario’ s point towards wetter winters, summers with heavy rains and sea level rise. Governmental institutions, sectors and citizens are not enough aware that reducing the risks of flooding is a shared responsibility.
In the Walloon region a prevention plan on flooding was approved in 2003 (PLUIES-plan of ‘Prévention et LUtte contre les Inondations et leurs Effets sur les Sinistrés’ – Prevention and fight against flooding and their impact on the victims). This global plan aims to improve the knowledge on the risk of flooding, to reduce and delay the drainage of water on slopes, to improve river management, to reduce the vulnerability of flooded zones and to improve the crisis management. Supervision in real time of watercourses, hydrological studies, coordination and flooding alarms are already operational. The PLUIES-plan will be amended to convert the European directive on flooding. In the future flooding management plans (PGRI: Plan de Gestion de Risques Inondations) the principles based on the 3 P’ s (Prevention, Protection and Preparation) will be integrated.
In the Brussels region the regional water management plan 2016 – 2021, contains preventive as well as curative actions. These preventive measures contribute to a better adaptation of the built-up area to increased precipitation through better seepage of the soil and temporary retention of water on the parcels. This measures also permit the recuperation of rain water and an increase of seepage and evapotranspiration (limitation of paved surfaces, use of permeable material, green roofs,…)
The ‘blue network’ program was initiated in 1999 and aims to restore the continuity of the hydrological network and to re-import the buffer function through the recuperation of the drainage water. In the region the network for water drainage is a unitary type: the sewerages and drains do not only drain wastewater but also water from arched rivers and draining water. The disadvantage of this system is that with dry weather or limited precipitation the wastewater that arrives at the purification station will be unnecessarily diluted and on days with heavy rains the system will get blocked and causes flooding with highly contaminated water. The program improves the rivers, ponds and water rich zones in the urban area.
The most important curative measure is the construction of a range of storm basins, connected to the sewerage network. When heavy rains occur, these basins can save the drainage water to restore the flow rate in the sewerage network.
Compensation measures for impermeabilization on the field are systematically incorporated in the construction permit for retention or absorption of runoff water.
At the federal level the coverage of flooding and other natural disasters is since 2007 included in the fire insurance policy. The Royal resolution of 28 February 2007 defines risk areas based on regional maps. If a new building is constructed in an area of risk, the insurer is not obliged to offer coverage against flood damage. For existing buildings in areas of risk there is a solidarity mechanism to limit the premiums by distribution of the costs under all insured parties. Although the main objective of the government isn’t climate change adaptation, it has a dissuasive effect on residential building in areas with a high risk of flooding. Flood maps are available for the three regions.
To reduce the risk on water scarcity in Belgium, sustainable solutions connected to the water system are preferable following the principles of multi-layered water security with special attention to protective, preventive and preparative measures that try to balance the water demand and offer. The reduction of the risk on water shortage is a shared responsibility of governments, sectors and citizens.
The policy on water scarcity and drought targets the objectives of the Water Directive and the limitation of damage caused by water scarcity and drought. This directive obliges the member states to sustainable use of water. Therefor they must develop management plans for each river basin.
In Flanders the Coordinating Commission for Integral Water Policy has been appointed as drought coordinator in June 2017 to guarantee the necessary consultation and tuning between the measures during a period of drought. In June 2018 the Flemish commission on drought has been installed. In case of extreme drought there must be priority rules available for water use. Therefor consultation of the different actors has been initiated.
In the Brussels region, since 2004 monitoring at river basin level is combined with quality monitoring. The regional water management plan has been adopted in 2017 and aims to find an integrated and global approach for all the challenges in water management for 2016 till 2021. This plan provides measures to stimulate the sustainable use of water and to restore the hydrographical network of the region. It also contains a program for rational water use in urban areas, developed in the context of sustainable urban design and ecological construction projects.
Project Flood4Cast (VITO) to better anticipate possible flood scenarios
Project “Flooding: prediction of flooding“
Horizon 2020 project BINGO: Bringing INnovation to onGOing water management – a better future under climate change (2015-2019) aims to provide practical knowledge and instruments to end users, water managers and policy makers who have to deal with climate change, in order to better adapt to the effects of climate change including droughts and flooding