河流裂点的发育及其溯源迁移: 以鸭绿江-望天鹅火山区为例

Abstract

Initiation and recession of the knickpoints are significant boundary condition for processes of fluvial system. The distribution and recession rates of knickpoints contain information that provides a fundamental understanding of geomorphic processes. In the Yalu River-Wangtian'e volcanic region of northeastern China, broadly distributed flat lava terrain provides an ideal site to study the recession of fluvial knickpoints because knickpoints and waterfalls are well preserved here. Here we describe the distribution of knickpoints in the Yalu River-Wangtian'e volcanic region by combining DEM analysis and numerical modeling. Furthermore, we present a knickpoint celerity model, derived from stream-power incision model, to relate knickpoint recession rate to drainage area. We calibrate important empirical coefficients with our knickpoint celerity model; the best fit erosion coefficient (K) is 1. 32×10-8, and the best fit drainage area exponent (m) is 0. 69. Error analysis indicates a close correspondence between synthetic and real knickpoints. Finally, we show that knickpoint recession rates in the Yalu River-Wangtian'e volcanic region are ~1-10 mm/a during the early stages of transient incision, and that the present rates are ~1-6 mm/a. Our recession rate results are in good agreement with previous findings from the Aso Volcano and volcanoes near Boso Peninsula (Japan), which have a similar geologic history to the Yalu River-Wangtian'e volcanic region. Our present effort provides new insight into landscape evolution in the Yalu River-Wangtian'e volcanic region in northeastern China. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.