Observation and Analysis of Rainfall-Runoff Characteristics in a Coastal Granite Catchment in Southern China

Abstract

Soil texture characteristics of a small coastal granite catchment in the Pearl River Basin in southern China were analyzed, revealing loamy sand and sandy loam as the main soil types in this catchment. Rainfall-runoff processes were then analyzed on the basis of the observation of precipitation, runoff yield, and soil water content at two experimental plots in this catchment. The two study plots represented forest and shrub cover, respectively, and both were underlain with highly weathered granite. Average runoff yield coefficients for the forest and shrub plots were 0.113 and 0.042, respectively. A relatively large proportion of interflow was generated only when rainfall was sufficiently large in amount or intensity. A logarithmic relationship existed between precipitation and the maximum infiltration depth for plot A. The main direction of rainwater movement at plot scale was vertical. The runoff yield was composed primarily of infiltration excess overland flow and interflow at the plot scale, whereas overland flow (saturation excess overland flow generated near the stream), interflow and bedrock fissure flow were the main storm flow components of this granite catchment.