Evaluation of the Potential for Roof-Scale Rainwater Harvesting in Terms of Sustainable Urban Water Management: The Case of Recep Tayyip Erdoğan University Güneysu Housing Complex

Climate change, rapid urbanization, the increase in impervious surfaces, and interventions in natural drainage systems are making rainwater management an increasingly important planning issue in coastal cities. Particularly in coastal cities with high precipitation regimes, sloping topography, and dense stream networks, rainwater should be considered not only as an element that creates surface runoff and flood risk, but also as a water resource that can be utilized. This study aims to determine the roof-scale rainwater harvesting potential in the case of Recep Tayyip Erdoğan University (RTEÜ) Housing Complex located in Güneysu district of Rize province and to evaluate this potential in terms of sustainable urban water management. Within the scope of the research, the roof surfaces of a total of 39 structures, consisting of housing blocks, a guesthouse, a mosque, social facilities, and auxiliary buildings, were examined. Roof areas were determined using AutoCAD base maps, Google Earth Pro data, and field observations; the rainwater harvesting potential was calculated using long-term monthly precipitation data for the period 1993–2023. According to the findings, the total roof surface area in the study area is 26,717 m², and it was determined that 49,830.6 m³ of rainwater can be harvested annually from these surfaces. It was determined that the rainwater harvesting potential is not homogeneously distributed throughout the year, that the highest values occur in the autumn months, and that 36.16% of the total annual potential is obtained during this period. The results show that roof-scale rainwater harvesting in RTEÜ Housing Complex has significant potential both in terms of creating an alternative water source and contributing to the reduction of surface runoff during periods of intense rainfall. In this respect, rainwater harvesting can be considered an applicable strategy that can be integrated with green infrastructure, sponge city, and climate-resilient urban water management approaches in high-rainfall coastal cities.