Essential strategy for urban seasonal-river restoration

摘要

Recently, many urban rivers are being restored due to positive environmental effects while debris flow may occur in seasonal-rivers of cities in arid regions. Therefore, as a part of river restoration studies, the impacts of debris flow on an urban seasonal-river (Vardavard River, Tehran) were analysed based on field investigations and hydrologic, hydraulic and sediment analyses. The results show that high-concentration of sediments in debris flow increases peak flow and hydraulic roughness, resulting in river flooding. The steep slope of the river basin increases the debris flow peak up to 1.2 times more than an ordinary flood peak with the similar return period. Hence, designing a slit dam before the river enters the city is suggested as an essential strategy to control the debris flow and improve safety of the downstream urban areas. The proposed approach, with enforced watershed management schemes, can be implemented to restore other urban seasonal-rivers and to prevent probable debris flow in arid regions.