SAMUWA - city as a hydrological system in transition - Steps towards an adaptable management of the urban water balance | Umweltbundesamt

The processing climate change challenge today’s cities in regard to heavy rain, heat stress and drought periods. At the same time increasing urbanization and the increasing land coverage influence the water balance and the drainage system negatively. This decreases the living quality of the majority of cities due to extreme flooding events and therefore worsening urban climate, worse air quality and missing retreat options into green spaces. Disciplines of urban water management and the urban and open space planning have developed individual strategies and instruments in order to cope with such problems. In order to meet prospective changing processes (climate change, demography…) and challenges (land scarcity,…) efficiently a water-sensitive urban development with multifunctional land uses is required.

There the need for action due to risks and hazards. Opportunities and potentials should be put into focus by using funding measures which can lead to a better water balance and flooding precaution. The simulation tool WABILA or DYNA / GeoCPM is used in order to create integrated strategies and concepts for measures which can identify shortcomings in water balance and plan measures for rain water management. DYNA / GeoCPM can build 1D / 2D can network- and surface runoff models by calculating the hazard potential for floods and the damage potential on specific land uses.

The usage of the modelling forms priority action spaces.

On the basis of the balancing and simulation of the status quo situation in terms of water management, large scale strategies for the city or for river sheds respectively can be developed, focus areas with need for action can be identified and prioritized and small-scale measures can be developed, revised and repetitively optimized. Thus, financial costs for infrastructural work can be reduced and measures of above-ground attractive design of open spaces in housing estates, industrial areas, roads or on commercial sites can be combined to increase the (useful) value of the land.

An urban development model with water-related elements serves as a basis for working and decision-making for the development of multifunctional surface design and sets out basic urban development directions, taking into account spatial potentials for rainwater management or flooding prevention and flood hotspots, heat islands, noise and air quality. The model projects were applied to two model areas Gelsenkirchen and Wuppertal.