Importance of drainage density and stream network ordering schema of drainage basin; a micro catchment-based analysis

Abstract

Protection of upper catchment areas has importantly been becoming challenged since the forest cover of upper catchment areas has been eroded dramatically for years. Especially, due to the expansion of anthropogenic activities in the upper catchment areas in Sri Lanka, soil erosion, soil degradation, and soil loss have come to the fore. This circumstance directly affects the natural river systems. The key objective of this research was to analyze the drainage density and drainage richness of the Kukule upper catchment and its micro catchments. For the methodological approaches, this research considered the drainage density and the purification ratio, in addition to the examining of river stream orders invented by A. N. Strahler (A. N. Strahler’s River Network Classification Law). The cartographic applications, such as the topological significance (e.g. elevations and water divides, etc.) and mapping of catchment areas have been prepared based upon the Geographical Information System environment. According to the results, the Kukule catchment was identified as a rich catchment in drainage density and purification ratio. The Kukule catchment is identified as a fifth-order river basin that consists of higher numbers of stream segments and nodes. This may be because a part of the catchment belongs to the Sinharaja tropical evergreen forest reserve.