Micro-landform classification and flood hazard assessment of the Thu Bon alluvial plain, central Vietnam via an integrated method utilizing remotely sensed data

Abstract

In this study, we developed an integrated method for classifying micro-landforms and flood hazard zones based on a geomorphological approach utilizing Shuttle Radar Topographic Mission (SRTM) and LANDSAT ETM + (Enhanced Thematic Mapper Plus) data combined with field investigation. Micro-landform units on an alluvial plain were classified in relation to flood conditions by integrating an SRTM digital elevation model (DEM) with spectral characteristics from a pair of LANDSAT images from dry and flood seasons. In addition, the LANDSAT ETM + band4-band3 of the flood season image was calculated to identify moist surfaces. Next, a flood hazard zonation map was generated by categorizing geomorphological features and the average elevation of each landform into flood hazard classes. Then, three-dimensional (3D) diagrams of the composed maps were produced using GRASS 6.3 to visualize the geomorphology and flooding risk. The results were validated using field surveys, topographic maps and past inundation images. This case study was undertaken for the Thu Bon alluvial plain, central Vietnam. The findings of this study revealed a close interaction between the geomorphological characteristics of this region and flood conditions. Flooding and sedimentation mechanisms cause dynamic formations of fluvial and coastal landforms, and these geomorphological features in turn affect flood hazard. Furthermore, 43.34% of the area of this plain is classified as having a very high or high flood hazard in lowland areas and a flash flood hazard in higher areas.