Improved continuing losses estimation using initial loss-continuing loss model for medium sized rural catchments

Problem statement: The rainfall based design flood estimation techniques are commonly adopted in hydrological design and require a number of inputs including information on soil loss characteristics. Approach: A conceptual loss model known as the 'Initial Loss-Continuing Loss (ILCL) model' is widely used in Australia. Results: The Initial Loss (IL) occurs at the beginning of the rainfall event, prior to the commencement of surface runoff and the Continuing Loss (CL) is the average rate of loss throughout the remainder of the storm. The currently recommended design loss values depicted in “Australian Rainfall and Runoff Vol. 1” for Queensland (Australia) has some basic limitations. This study investigated how more accurate CL values can be estimated and derived for medium sized tropical Queensland catchments using long term rainfall and streamflow data. Accuracy in CL estimation has got significant implications in the estimation of design floods. Conclusion/Recommendations: The results showed that CL value is not fixed and constant through out the duration of the storm but the CL value decays with the duration of the storm.