Significance of combining SRTM DEM and satellite 1 images for generating automated micro - landform map

17 Abstract—This study outlines a method for generating an 18 automated micro-landform map of an alluvial plain for 19 further flood hazard assessment by combining Shuttle Radar 20 Topographic Mission Digital Elevation Model (SRTM DEM) 21 and satellite images. Average elevation and channel features 22 extracted from DEM are associated with soil moist condition 23 (thresholds of Modified Normalized Difference Water Index 24 – MNDWI) from remotely sensed images based on a logic 25 rule. This process is conducted in GRASS GIS. SRTM DEM 26 is known as consistent and useful data for landform mapping 27 by digital terrain analyses. However, because of its limitation 28 in spatial resolution, satellite images are combined to isolate 29 micro-landforms in alluvial plains (flat and low relief). 30 Another merit of this automated method in comparison of a 31 manual method is time-saving, objective and simple for 32 editing. Although, theoretically, manual mapping by aerial 33 photos and topographic maps combined with field survey is 34 definitely more accurate; in fact it subjectively relies on 35 human interpretation. Meanwhile the automated mapping 36 process is rather objective, as a result create more accurate 37 boundaries of landform objects of large-size units such as 38 terraces, sand dunes but less detailed in small-size units such 39 as natural levees. A case study is conducted in the alluvial 40 plain of the Vu Gia-Thu Bon River, central Vietnam. 41