A Numerical Simulating Research Of The Response Of Fluvial Landscape To Long-term Climate Change And Tectonic Uplift Events

Tectonic uplift and climate change are two major factors which have effect on landscape evolution. With development of computer technology and knowledge of surface processes in advance, some scholars started using numerical simulation technology to study the relationship between landscape evolution and the two major factors - tectonic uplift and climate change. Numerical simulation has been used in many scientific areas but little in geosicence until recent decades. In China, there was almost none relative study invovled in long-term landscape evolution. And those existed researches more focused on low-altitude areas with sand-bed rivers than high-altitude areas with stong uplift and gravel-bed rivers. So, we developed a long-term landscape evolution model based on physical theories and applied it to Shagou, a little drainage which located on Eastern Qilian Mountains. Through numerical experiments with different settings, we explored how river has response to tectonic uplift and climatic change and how these two factors have effect on landscape evolution and tried to enrich experiences in numerical simulation in geoscience.At first, we simulated how fluvial long-profile has response to climate change and tectonic uplift in different conditions and found that (1) fluvial long-profile is sensitive to bedrock erodibility (kb) and initial profile has little effect on experiment results; (2) with no tectonic uplift event, the largest water discharge in river caused by climate change determines the shape of fluvial equilibrium long-profile; (3) with climate not changing, the magnitude of tectonic uplift and the location of fault determine how long time needed in split spot migration and how quick the split spot migrates, respectively; (4) when tectonic uplift event occurs with climate changing, river generally has complex response process. Fluvial long-profile would adjust again and again and reached few equilibrious stages.Considering that hillslope processes and lateral sediment inflow would influence sediment transport process in river, we developd a 2-D drainage landscape evolution model and did some numerical experiments with different settings. After analyzing results, we found that (1) study area is not sensitive to routing algorithms, different algorithms used to calculate gradient have effect on results and different spatial resolution of DEM, which used as initial condition, has great effect on results; (2) drainage surface is sensitive to rapid climate change when no tectonic uplift event occurs; (3) With climate not changing, single tectonic uplift would be the main factor which causes changes of drainage form.