Investigating the potential of urban runoff by zoning using SCS-CN Method (Case study: Region 2 of Tehran Municipality)

Urban development reduces the permeability and increases surface runoff. The Increased runoff has encountered urban areas with many threats on the one hand and provided an opportunity on the other hand and both necessitate the management of runoff in urban areas. Zoning of rainfall and runoff are undeniable because of the major land uses in Region 2 of Tehran city which includs residential land uses, highways, and green space respectively for various return periods in order to identify those areas with high potential for surface runoff to achieve management goals.
The method employed in this study is SCS-CN in GIS software based on Maximum 24-hour rainfall data for a time period of 14 years collected from Rain-gauge stations around Region 2 of Tehran.
Findings: The findings are determination of a common statistical period between stations used, homogeneity test, adequacy, reconstruction of incomplete data to calculate the return periods of 100, 50, 25 and 5 years to conduct zoning for the maximum 24-hour rainfall, and also construction of curve number layer based on the type of land use, effective coefficient, penetration and retention of surface using relations in the model to conduct runoff zoning in various return periods.
The results show that the highest potential for generation of runoff is related to residential and highway land uses in eastern part, and the lowest potential is related to slopped parts in the central and north districts with green space land use that should be put under management priority. This indicates the importance of land-use in creating the potential of runoff, so that this importance makes the prominent factor of slope totally ineffective.