Rainfall Runoff Modelling of Urban Area Using HEC-HMS: A Case Study of Hyderabad City

Abstract

Uncontrolled urbanization and climate change play a significant role in urban flooding. The condition in which rainfall excess exceeds the drainage capacity of storm water drains is called urban flooding. Urbanization disrupts the natural water balance by increasing impervious areas and reduction in infiltration. This increases runoff from urban catchments and leads to higher flood peaks even for short-duration low-intensity rainfall. Such flash floods significantly increase the expenses on mitigation efforts owing to their destructive nature. Urban flood management is one of the important topics of concern as frequent disasters are happening in almost all the urban areas. This is the indication of poor storm water management in urban areas particularly in developing countries like India. Thus, to improve the situation proper storm water drains and sewage network need to be planned and installed considering present land use pattern and probable future development. Present study focuses on the simulation of critical storm event for analysing drainage capacity for part of Hyderabad city (Zone XII). This study area is the most flooded catchment in Hyderabad, and it is ranked as priority number 1 in urban flooding. The drainage network exists in certain parts of the study area. Rainfall data is collected from the Indian Meteorological Department (IMD), and extreme rainfall events are found out. The response of the catchment to the extreme rainfall is modelled using HEC-HMS and HEC-Geo HMS. The simulated model gives a peak discharge of 590.5 m3/s at the outlet (Hussain Sagar Lake) for the August 2008 rainfall event having 221.4 mm precipitation for the duration of 34 h.