Abstract:
Rational Method is generally used for estimation of peak discharges. Different
authors mentioned different catchment area limitations for use of rational method
with respect to different locations due to variation in precipitation rate and variation of ground characteristics. Mostly, the researchers stated that the results from
this method could be acceptable upto area limitations of 200 acres. However, there
is need to evaluate the applicability of rational method with respect to catchment
area for Islamabad region to check the application and catchment limitations for
the design of storm drainage system in future. Digital Elevation Modeling (DEM)
along with other helping tools like Global Mapper, Sam-Sam water harvesting
have been used to estimate runoff by rational method. Different points of interest
developed with drainage areas of 663.8 acres, 805.4 acres, 1056.9 acres and 1529.0
acres. Then, corresponding value of runoff coefficient “C” is calculated with respect to type of drainage area. Discharge from rational method was estimated
for all points of interest. Then, the results were compared with Soil Conservation
Service (SCS) Curve Number method applied to same catchments. The results
obtained from comparison showed that Rational Method approach could be applicable for larger areas with respect to characteristics of the ground and type of the
area i.e. for developed areas. Readers will be able to evaluate the applicability of
Rational Method approach after going through this research work.
