The impact of watershed characteristics on flood behaviour in the Noelmina River region

Abstract

Timor Island has two river regions, one of which is the Noelmina River Region. There are 91 watersheds in the Noelmina River Region, covering a total area of 5,418.85 km2. Each watershed possesses unique characteristics that influence the amount of flood discharge. The key watershed features that can be analysed to assess their impact on floods include shape, area, river length, slope of the watershed, slope of the river, and runoff coefficient. The aim of this study was to identify the specific characteristics of watersheds within the Noelmina River Region that contribute to significant flood discharge. The study focused on examining 20 watersheds within the Noelmina River Region, utilising spatial data such as the Timor Island DEM, land use, and hydrogeological map. The rainfall analysis was performed using the Log Pearson III distribution method with a return period of 500 years. Analysis of flood discharge using the SCS-CN method. The results obtained are that the shape of the watershed, the land use, and the curve number values have a greater impact on the amount of flood discharge produced. The time required to reach peak flood discharge in the Noelmina River Region typically ranges from 7-12 hours.