CSDMS 2013 annual meeting poster Jianwei Han

Presentation provided during CSDMS annual meeting 2013

Exploring the mechanisms that control valley spacing in higher order fluvial channels with the CHILD Model

Jianwei Han, Tulane University New Orleans Louisiana, United States. jhan@tulane.edu
Nicole Gasparini, Tulane University New Orleans Louisiana, United States. ngaspari@tulane.edu


Previous studies have found that the ratio between valley spacing and mountain range width is relatively constant across the globe, but the processes responsible for its uniformity are not well understood. To determine the reasons for this uniform ratio, we firstly need to explore why valleys are evenly distributed in a mountain range, and what factors can impact valley spacing. Recent research has found that the critical length between hillslope and fluvial processes is an important control on the valley spacing of first order fluvial channels. In this study, we use the CHILD landscape evolution model to explore how the critical length affects valley spacing in higher order fluvial channels, and we use these results to help explain the narrow range of observations in the valley spacing ratio. We find that valley spacing has a linear relationship with critical length in higher order channels and, for a given order channel, the ratio between valley spacing and critical length is relatively constant. This relationship demonstrates that the competition between hillslope and fluvial processes influences the distribution of higher order channels across the landscape. However, we also find that valley spacing is influenced by model initial conditions and variability across the landscape, such as orographic precipitation patterns. Moreover, for a fixed domain in our model, although the critical length may vary, the ratio between the valley spacing of trunk channels and mountain width remains in the range observed in real landscapes. The reason for this is that the order of trunk channels varies with the critical length. Therefore, for a given domain size (or mountain range width), a larger critical length can produce lower order trunk channels but with the same spacing value as higher order trunk channels with a smaller critical length. This may be one of the reasons why the spacing ratio is relatively constant across diverse natural settings.

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