Forecasting river bank erosion with regards to rainfall erosivity and soil erodibility

Abstract

Riverbank erosion is one of the major and unpredictable problems worldwide. The erosion involves the wearing away of soil found along the river bed and it can take place due to the occurrence of heavy rainfall, strong stream flow and weak river bank soil. The purpose of this study is to categorise the river bank erosion at the study area based on two main factors, namely, rainfall erosivity and soil erodibility. With rainfall data records for 9 rainfall stations along Langat River, a daily rainfall amount analysis and ‘ROSE’ index software application (after the name of the researcher ROSlan and Ezanie) were used to forecast the erosion risk potential along the Langat River bank. The results indicate that the highest rainfall erosivity is from the month of March to April and September to November. The soil resistance against erosion, termed as soil erodibility, depends on several factors, such as soil textural composition, soil infiltration level and organic matter content. Sieve analysis and hydrometer tests were conducted for all the soil samples collected at every 2 km interval on both sides of the river bank and the “ROM” scale (after the name of researcher ROslan and Mazidah) is used to determine the degree of soil erodibility, namely low, moderate, high, very high and critical. The results indicate that the soil erodibility with a high, very high and critical category for both sides of Langat River bank were at the upper and middle stream of Langat River, which is in the Hulu Langat and Sepang districts. Thus, this would benefit the country in terms of cost reduction in river bank protection; besides, the relevant authorities can take early measures to overcome river bank erosion failure.