Evaluating the effect of water harvesting methods on urban runoff (Case study: Birjand urban watershed)

New approaches to urban runoff management seek to reduce the volume and discharge of rainfall peaks as well as the amount of pollutants in urban areas to a level that is reminiscent of rainfall runoff in the decades before urban development. SWMM software is one of the best models to help in this field and it can be used to study the effects of using water harvesting methods on the volume of runoff and peak flow and thus reduce flooding of roads. Simulation of the drainage network in the north of Birjand city showed that the sewerage network of Birjand city does not have the necessary efficiency to pass floods with different return periods and is flooded in different parts. If the problem is not solved by the relevant organizations, in the not too distant future, it will witness a large flood and as a result, irreparable damage will be undeniable. For this purpose, using two methods of holding ponds and collecting water from the roofs, which can be used at a lower cost than other methods of water extraction; , in this study was examined. Considering that the use of water extraction systems in the whole basin is economically unfeasible and justified. In most studies, this system is used only in a part of the field. As a result, by applying rainwater extraction methods in Birjand urban watershed, we can see an 80% reduction in runoff volume in Birjand. On the other hand, the use of ponds in the green space of the city can help irrigate the green space and in addition to saving urban water consumption, is also effective in reducing the peak discharge of floods.