A GEOGRAPHIC INFORMATION SYSTEM BASED SPATIALLY DISTRIBUTED RAINFALL - RUNOFF MODEL

The two most important parameters required to design many hydraulic structures and systems like dams and sewer systems are the peak discharge and the time to the peak discharge. To estimate these parameters hydrologists develop rainfall-runoff models. Traditionally most of these models assume uniform rainfall distribution and constant watershed characteristics. Though these lumped models are easy to work with and do not require large amount of memory and time, the results obtained from such models can be improved by working with spatially distributed rainfall and watershed characteristics. In this research such a spatially distributed rainfall-runoff model has been developed. The developed model is based on the time-area unit hydrograph method. The SCS (Soil Conservation Service) (now named Natural Resources Conservation Service) Curve Number data set for the whole watershed is developed using the soil and the land use data. Then based on the curve numbers, the runoff is computed from the rainfall that falls in the watershed. The amount of runoff being generated in a particular time interval is identified and is used to develop the time-area diagram from which the runoff hydrograph is generated. The objective was to develop the curve numbers for the watershed automatically using GIS and the soil and land use data and to use these curve numbers to get the distributed runoff being generated in the watershed. Such an approach would remove many limitations of the unit hydrograph method that has been the basis of many traditional rainfall-runoff models.