Urbanization Challenges in Emerging Economies

Abstract

The unit hydrograph (UH) concept needs observed rainfall-runoff data at the gauging site for hydrograph generation. But many catchments and watersheds in India are devoid of gauging stations and also it is not economically justifiable to collect the data and carry out detailed hydromorphological studies at every new site on a large scale. The paucity of such data sparked the idea of the synthetic unit hydrograph (SUH) concept. Most SUH procedures seek to establish relationships between parameters used to describe the UH and parameters used to describe the basin. In totality the available synthetic unit hydrograph methods/models have been classified into four groups as: traditional (or empirical), conceptual, probabilistic, and geomorphological. In the present study the probabilistic or probability distribution function (PDF) based methods/approaches are used to estimate the flood discharge at the ungauged basins in Varrar Basin at the coastal state of Kerala. The PDF based methods viz. Gray's method, Croley method, transmutation approach, and simplified gamma approach are used to develop UH at ungauged watersheds. The results of the total flood discharge at the ungauged basins are compared with volume of 1 cm direct runoff depth. © 2018 American Society of Civil Engineers.