Assessment of annual high-discharge patterns in Kapuas River using information and complexity measures

Abstract

A recent study revealed that the amount of rainfall on the Kapuas River has increased over the last 30 years. The increase in rainfall increases the possibility of high discharge events, which might lead to destructive flooding of the Kapuas River and its tributaries. Hence, the ability to characterise the pattern of high discharge events is compulsory for the development and management of the Kapuas River watershed. The main objective of this study was to assess and characterise flood patterns in the Kapuas River watershed. To achieve this objective, we utilised information and complexity measures that consisted of mean information gain ( MIG), effective measure complexity ( EMC) and fluctuation complexity ( FC) in daily water level records from 2002 to 2011 from a gauging station in Sanggau, West Kalimantan Province. The results revealed that flood events in the Kapuas River were mainly generated by the Indo-Australian monsoon, which occurred from December to March. The anomaly in 2010, when intense flood events were observed during the dry season, can be identified as the effect of a strong negative El Niño-Southern Oscillation (ENSO). Additionally, the analysis of the information and complexity measures indicates that: (i) EMC, which reflects the length of flood events, tends to increase along with greater discharge, and (ii) MIG and FC, which denote the degree of randomness and fluctuation of flood events, respectively, tended to have higher values when the number of months without high discharge was less.