Abstract

Facilitating and improving decision-making in urban stormwater management is a key goal of the interdisciplinary research project “Concepts for urban rainwater management, drainage and sewage systems” (KURAS). By reinstating a more natural hydrological cycle, by increasing infiltration, evapotranspiration and stormwater reuse at the building or neighborhood level, e.g. via green roofs, pervious surfaces, swales and artificial ponds, to name but a few, stormwater management has the potential not only to reduce flooding and river degradation but also to improve landscape and habitat quality, the urban climate and resource efficiency, to reduce costs, and to respond more flexibly to uncertain future conditions. These multiple potential benefits have been valuated in a systematic way, thus providing a quantitative and comparative assessment of the effects of the various approaches to stormwater management as a basis for decision-making. An important element is the stakeholder involvement in planning in order to expose interests, resolve conflicts and to discuss existing financial, legal, administrative and knowledge-related barriers to adapted urban stormwater management. For two representative neighborhoods in Berlin, Germany, alternative and realistic stormwater management scenarios have been developed based upon an analysis of the current state and evaluated using the effect indicators. Central actors for stormwater management in Berlin are collaborating with other stakeholders in the sample neighborhoods to formulate and prioritize goals regarding the selection of measures, to discuss the evaluation results and to develop transition strategies. The presentation will focus on this experience of stakeholder participation in the design of stormwater management systems on the neighborhood scale. It will present preliminary findings to be translated into recommendations for policy makers and practitioners.

Abstract

Im Rahmen eines Planspiels wurden für ein Stadtquartier Kombinationen der Regenwasserbewirtschaftung erstellt und wissenschaftlich bewertet. Die verwendete Methode kombiniert dazu lokale Bedingungen (Problemlage, Machbarkeit von Maßnahmen und lokale Ziele) mit einer Bewertung von 27 Einzelmaßnahmen hinsichtlich ihrer vielfältigen Effekte. Die Ergebnisse zeigen zunächst, dass eine skalenübergreifende Kombination von Maßnahmen vom Gebäude bis zum Kanaleinzugsgebiet ein großes Potenzial für die Verbesserung der städtischen Umwelt (Gewässer und Biodiversität) und Lebensqualität (Stadtklima, Freiraumqualität, Nutzen auf Gebäudeebene) hat. Die verwendete Methode erwies sich als gut geeignet für die Auswahl effektorientierter (und machbarer) Maßnahmen und für deren gezielte Platzierung in Problemräumen. Die Erfahrungen zeigen aber auch, dass die Methode optimiert werden muss, um eine bestimmte Zielerreichung (z.B. Kostenrahmen oder Einleitbeschränkung) während der Planung zu berücksichtigen.

Abstract

A total of 27 existing measures of stormwater management were studied across scales from building level (vegetated buildings, rainwater use) to city quarter level (infiltration, de-paving, artificial lakes and streams, decentralised treatment) and catchment level (centralised treatment, storage). For each measure, the same performance indicators were quantified based on literature, monitoring and simulation results regarding six potential benefits (water/energy saving potential, improvement of landscape quality, increase in biodiversity, reduced urban heat exposure, improvement of groundwater and surface water bodies), indirect resource use (life cycle assessment) and direct cost. Results show that each measure has its strengths and weaknesses. Thus, it is expected that different combinations of measures will lead to increased benefits for different locations/settings. The developed measurebenefit/cost-matrix may support the finding of such improved combinations and is currently tested in a research project regarding its potential for problem-oriented urban planning in Berlin, Germany.

Abstract

Integrated planning of stormwater management requires a quantitative description of positive and negative effects of possible measures. We suggest quantifying these effects with generic performance indicators within eight categories: building physics and services, landscape quality, urban climate, biodiversity, groundwater, surface water, direct costs and indirect environmental costs. First results indicate that the defined performance indicators allow an objective pre-selection of measures based on their ability to reach local stormwater management goals. The final selection of measures should be based on an evaluation for a specific city quarter (to reduce indicator uncertainty) and reviewed by local stake holders.

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