Sustainable management of urban water resources through water sensitive urban design (WSUD) in Iran (case study: Rasht city)

Introduction:
So far, the use of water sensitive urban design (WSUD) has not been investigated in cities of Iran. This issue, for the first time introduced in Australia in 1994, has been implemented in several countries, such as America, Germany, the Netherlands, and Australia. The main objective of WSUD is to establish a link between urban planning and design, and landscape design with sustainable management of water flows in a city.  In other words, this approach tries to revitalize the natural water cycle in the city by presenting urban design-oriented solutions that may have less environmental damages.
Material and methods:
In this descriptive-qualitative research, the WSUD approach has been firstly addressed; then, its indicators, as integrated water management factors, have been extracted, evaluated, and analyzed in the rainy city of Rasht. In addition, based on findings of the study, some strategies for improving the water management in the city of Rasht have been proposed. Since the extraction of its dimensions and indicators depends on an accurate and exact investigation of the resources and documents, data collection was done by a documentary study. In order to infer the repeatability and validity of the extracted data from the documentary texts, the content analysis was used. The extent of the significance of indicators is not the same. Therefore, after extracting dimensions, components and repeated indicators of integrated water management, the coefficients of the significance of each level at a higher level, based on obtained data from content analysis, have been calculated by data from the experts’ questionnaire (Delphi) which is 5-point Likert scale method. At last, the significance of each indicator was determined.
Results and discussion:
Based on the findings obtained from experts’ questionnaire, the environmental indicator was the most significant factor in sustainable urban water management, as well as urban river health and rate of rainwater storage with weights of 0.0469 and 0.0463, respectively. To analyze the present situation in Rasht city, observation, questionnaire, and statistical databases in the form of Swat Table were utilized as the instrumentation. By weighting the internal and external factors, based on the GOSP matrix, appropriate strategies were introduced in the group of adaptive strategies. In addition, prioritization was done by QSPM matrix strategies on different levels. Ultimately, appropriate policies for applying the water-sensitive urban design approach were made in Rasht city. The outcomes of these strategies can be as follows: transformation of the gray infrastructure network of the city of Rasht into the green-blue infrastructure network, eco-revelatory of green infrastructures instead of underground pipelines, changing attitudes towards the links of water, nature and buildings, and increasing citizens’ awareness of the natural water cycle, preventing urban flooding in passages during rainfall, cleaning up the rivers of Zarjoob and Goharrood as well as wetlands of Rasht and making them the green corridors and major leisure spots, increasing green roofs, green walls  and green terraces that have positive effects on the city’s temperature, air quality, wildlife, and mental health, and reducing drinking water consumption for non-drinking consumptions up to 50 percent (i.e., reduction of five million liters of drinking water only by collecting and handling gray water or rainwater and utilizing it as for rainwater flush tanks of buildings), etc.
Conclusion:
The ‌WSUD approach, as the latest urban design approach for sustainable urban water management, has been developed for the management of surface runoff quality to a wider framework, i.e., for integrating urban water management in combination with urban design. It is noteworthy that it testifies that there is a possibility of managing surface waters in the city, in such a way that, in spite of existing more than 2000 mm rainfall per year, and even the flow of 200 mm on height over the passageways, the use of urban spaces is not disturbed.