Mathias Uhl

SUDS, LID, BMPs, WSUD and more - The evolution and application of terminology surrounding urban drainage

The management of urban stormwater has become increasingly complex over recent decades. Consequently, terminology describing the principles and practices of urban drainage has become increasingly diverse, increasing the potential for confusion and miscommunication. This paper documents the history, scope, application and underlying principles of terms used in urban drainage and provides recommendations for clear communication of these principles. Terminology evolves locally and thus has an important role in establishing awareness and credibility of new approaches and contains nuanced understandings of the principles that are applied locally to address specific problems. Despite the understandable desire to have a ‘uniform set of terminology’, such a concept is flawed, ignoring the fact that terms reflect locally shared understanding. The local development of terminology thus has an important role in advancing the profession, but authors should facilitate communication between disciplines and between regions of the world, by being explicit and accurate in their application.

Development of a simplified urban water balance model (WABILA)

During the last decade, water sensitive urban design (WSUD) has become more and more accepted. However, there is not any simple tool or option available to evaluate the influence of these measures on the local water balance. To counteract the impact of new settlements, planners focus on mitigating increases in runoff through installation of infiltration systems. This leads to an increasing non-natural groundwater recharge and decreased evapotranspiration. Simple software tools which evaluate or simulate the effect of WSUD on the local water balance are still needed. The authors developed a tool named WABILA (Wasserbilanz) that could support planners for optimal WSUD. WABILA is an easy-to-use planning tool that is based on simplified regression functions for established measures and land covers. Results show that WSUD has to be site-specific, based on climate conditions and the natural water balance.

Schritte zu einem anpassungsfähigen Management des urbanen Wasserhaushalts

Die städtische Wasserinfrastruktur wird zukünftig einem Wandel der Randbedingungen ausgesetzt sein. Globale Trends wie der Klimawandel und demografische Veränderungen werden von stadtspezifischen Entwicklungen überlagert. Beispiele dafür sind wachsende oder schrumpfende Städte, die Nutzung von Flüssen und Seen als Badegewässer oder der Umgang mit überflutungsgefährdeten Wohngebieten. In der Siedlungsentwässerung wiegen solche Entwicklungen besonders schwer, da sie derzeit auf sehr unflexible Systeme treffen. Im Verbundprojekt SAMUWA werden Wege aufgezeigt, die bisher statischen Ansätze in Planung und Betrieb von Entwässerungssystemen zu einem anpassungsfähigen dynamischen Management zu führen.

Model Based Estimation of a Natural Water Balance as Reference for Planning in Urban Areas

The water balance of urban areas differs considerably from the landscape water balance. Increased surface runoff, reduced groundwater recharge and evaporation change the hydrological regime, the morphology and ecology of water bodies close to the cities, the groundwater in the urban area and the urban climate. Today’s urban drainage systems are designed to prevent, reduce, drain, seep away, evaporate or discharge precipitation into nearby surface waters with considerable delays. In doing so, it follows the principles of the German Water Resources Act (WHG) and the objectives of the relevant technical regulations DWA-A 102 to keep changes in the natural water balance by settlement activities as low as ecologically, technically and economically acceptable. A reference for the “natural” water balance has to be defined as a planning objective in order to quantify the hydrological changes in settlements. As a suitable reference, we propose to use the water balance of the landscape of the associated ecoregion with today’s cultural land use without urban developments. This approach is more suitable to define local conditions than the water balance of the enclosed catchment. The presented calculation approach to define reference values of the water balance, uses soil and geological properties, precipitation and climate data and can be implemented and applied uniformly throughout Germany. The water balances in this study are simulated with the water balance model RoGeR. In this study, the developed approach is applied for five locations in Germany.