Investigating the spatial distribution of flood inundation and landforms using topographic position index (TPI) and geomorphon-based automated landform classification methods

Abstract

The landform of the region highly influences the dynamics of the flood and plays a crucial role in directing the water flow, affecting the speed and volume of runoff. Assam, located in northeast India, experiences floods yearly due to adverse climatic conditions and complex terrain features. The objective of the present study is to understand the landform classification of Assam using the topographic position index (TPI) and geomorphon-based automated classification of landform (ACL) method and its spatial distribution with slope, geology, soil, LULC, and flood inundation. The ACL method shows that gentle slopes or flat areas occupy the maximum area ranging from 56.17 to 68.10% for TPI‐based slope position classes, and for geomorphon, slope feature occupies 20.61–25.39% of the total area. The spatial distribution of TPI and geomorphon-based landform classification was different because TPI compares the elevation of a point to the average elevation of its neighbourhood, while geomorphon classifies the landscape into predefined landform classes based on terrain shape and the spatial arrangement of elevation values. In both models, valleys are the most dominant landform class and are mainly present in the Central and Barak valley of Assam. The built-up areas and waterbodies on vulnerable landform classes increase their flood susceptibility. About 38.08% of the inundated area was found in wide valleys and 31% of the inundated area lies under flat landforms. The present study can be effective in land use planning, sustainable natural resource management, disaster risk management, and mitigation strategies.