Climate atlas — Theme Water nuisance — Vulnerability buildings extreme precipitation

In case of heavy precipitation, the water depth at a building can become so high that the water flows inwards and causes damage. This map gives an indication of the risk of water in buildings in case of heavy rainfall, due to an extreme shower of 100 mm in 2 hours in the urban area of the province of Zuid-Holland. Build-up The maximum water depth simulated with 3Di (storm of 100 millimetres in 2 hours) is compared to the floor level per building. This floor level is derived from the AHN2 and 3 (height around the building). If the maximum water depth is higher than the floor level, there is a risk of rainwater inflow and damage into the building. We use the following class classification: » Small risk: 0-10 centimeters of water depth against the facade; » Medium risk: 10-25 centimeters of water depth against the facade; » High risk: more than 25 centimeters of water depth against the facade. The centimetres are intended as an indication, to indicate which buildings can be considered relatively more with regard to flooding due to heavy precipitation. In the modelling, only the current over the ground is often taken into account; drainage through the sewerage and open water is often not included. It is therefore possible that the bottlenecks presented may not always be recognised in practice (to that extent). No rights can be derived from absolute values. The results give a first indication of the likely degree of vulnerability of buildings in case of heavy rainfall.