Relationship between elevation changes in the NW Himalaya and bedrock uplift rate and hydraulic erosion rate

Abstract

The mountain range in the Himalayas is affected by both active continental collision and extreme, highly variable precipitation. Hence, it is an ideal natural laboratory to examine possible relations between tectonics, climate, and subsequent erosion. Using ArcGIS and MATLAB software, based on the SRTM-1 DEM with a resolution of 30m, the stream network of the four regions within the NW Himalaya area was extracted. I extracted the longitudinal profile, drainage area, stream gradient, and normalized steepness index of each river, and used the stream-power incision model to calculate the erosion rate. By linking the actual uplift rate with the steepness index, the relationship between these two factors can be obtained, and the bedrock uplift rate of each river can be calculated based on this relationship, then the elevation change rate can be obtained. The obtained maps of elevation change rate, maps of bedrock uplift rate, maps of erosion rate map and distribution maps of lithology, precipitation, slope, and local relief are superimposed spatially and compared. Then the main factors affecting the rate of altitude change can be analyzed. The main research conclusions are as follows: 1. By analyzing the steepness index distribution map of each study area, we found that the whole pattern shows a law of the main channel having a smaller steepness index value than the tributary, areas with a steepness index value of more than 400 are almost in the tributaries. This shows that the tectonic activity of the tributary is stronger than the main channel. 2. By analyzing the erosion rate distribution map of each study area, we found that the distribution law of erosion rates is the exact opposite of the steepness index, showing that the erosion rate of the main channel is significantly higher than that of the tributary, and the erosion rate of the main channel almost exceeds 15 mm/yr. 3. By analyzing the erosion rate distribution map of each study area, we found that almost all parts with predicted elevation change rates exceeding 10 mm/yr are in the main channel, which indicates that the erosion effect in the main channel area is far stronger than the tectonic uplift activity. 4. Comparing the rate of elevation change with factors that may affect the change in elevation, it is found that lithology largely affects the rate of altitude change, however, when there are other factors with greater influence, or when the impact of other factors reaches a certain limit, the impact of lithology can be ignored to some extent. On the other hand, the geomorphological factor (slope and local relief) is also one of the leading factors in the elevation change rate. However, the effect of precipitation on the elevation change rate is limited and even negligible in some cases.