Integration of geospatial technology for assessment of mangrove habitat and riverbank erosion

Abstract

Kilim River, Langkawi has been declared as Kilim Karst Geoforest Park by the United Nations Educational, Scientific and Cultural Organization (UNESCO) in the year 2006. This has increased the number of tourists to Kilim River. However, the growing number of tourist and tourist boats activity has caused riverbank erosion and threaten the mangrove forest habitat. Therefore, the aim of this study is mainly to assess mangrove habitat and riverbank erosion using integrated geospatial technology. This study assessed the Kilim River physical properties which include salinity, pH, soil properties and mangrove species distribution along the river. Additionally, this study also estimates and projects the effect of Sea Level Rise (SLR). The data were analysed to identify relative dominance, density and frequency of mangrove species using ArcGIS. Rate of riverbank erosion were analysed using ArcMap extension Digital Shoreline Analysis System (DSAS) within three different timeline of year 2005, 2012 and 2017. Five different Very High Resolution (VHR) satellite imagery were used which is QuickBird, Worldview-II, Pleaides, Spot 7 and Sentinel. The salinity distribution along Kilim River during high water show a stratified increment from Bat Cave (upstream) towards the river mouth but there are no significant changes of salinity in depth. While on low water the salinity is lower compared to high water. Percentage of clay particle in soil at upper stream shows higher percentage of 21% compared to middle and lower stream. The dominant mangrove species at Kilim River are Rhizophora apiculata and Rhizophora mucronata with bigger size of mangrove based on diameter at breast height (DBH) at downstream area while smaller DBH at the upstream area. Riverbank erosions are highest at the middle stream which cover the jetty area, however significant accretion shown at upstream which means mangrove start to migrate into the river. Significance rate of erosion is found at the jetty area and active navigation route of tourist boats especially at narrow width of river. The SLR projection in year 2030, 2050 and 2100 are 0.11 m, 0.22 m and 0.68 m, respectively. Results from the inundation map shows no significant inundation in year 2030 and 2050. However, for the year 2100, the area that will be inundated is about 9518 m2. In conclusion, this study has shown the result of physical properties for mangrove habitat, riverbank erosion and impact of SLR at Kilim River. Precaution measures should be planned by the local authority hence the status of popular tourism area and Kilim Karst Geoforest Park can be maintained.