The colluvial dimension of mountain drainage basins

本研究的重点是不列颠哥伦比亚省山区环境的崩塌沉积动力学。总体目标是推进目前对崩积沉积物通量和崩积-冲积相互作用的理解，这些如何影响当前的功能，以及山地流域的长期演变。该研究将在一个新颖的、多尺度的框架中调查山坡和河道，解决以下问题：(i)是什么控制了与滑坡和泥石流相关的崩塌沉积物通量？相关的泥沙供应如何影响山间河道的功能？（iii）山地流域大尺度构造如何影响崩积活动和崩积-冲积相互作用？研究将结合航空照片、数字高程模型和实地数据进行。第一个问题将通过考察滑坡震级-频率关系的时空控制及其对地形的相关反馈来解决。第二个问题将使用来自滑坡清单的信息，将通过以下方面的定量特征来解决：(1)滑坡通道的纵向剖面、横截面、木材负荷、粒度和水流功率指数；（ii）群落-冲积相互作用的时空变异性。第三个问题将在景观对引起滑坡扰动的外部强迫的响应的背景下解决，并将利用从前两个研究组成部分获得的数据。总的来说，这项研究对于理解森林实践对山涧的环境影响、流域泥沙动力学以及滑坡对河谷演变的影响将是非常宝贵的。特别是，我们将能够记录河道网络中滑坡扰动优先发生和沉积物储存的位置，物质储存多长时间，以及河流改造的效率。最后但并非最不重要的是，我们希望提高我们对流域结构如何控制滑坡产沙和与河流的相互作用的理解。

The proposed research focuses on colluvial sediment dynamics in mountain environments of British Columbia. The overall objective is to advance the present understanding of the colluvial sediment flux and colluvial-alluvial interactions, how these affect the current functioning, and the long-term evolution of mountain drainage basins. The research will investigate hillslopes and channels in a novel, multi-scale framework that addresses the following questions: (i) what controls the colluvial sediment flux associated with landslides and debris flows? (ii) How does the associated sediment supply affect the functioning of mountain channels? (iii) How does the large-scale structure of mountain drainage basins affect colluvial activity and colluvial-alluvial interaction? Research will be conducted by combining the use of aerial photographs, digital elevation models, and field data. The first question will be addressed via examination of the spatial and temporal controls on landslide magnitude-frequency relations and their associated feedback on topography. The second question, which will use information derived from landslide inventories, will be addressed via quantitative characterization of (i) colluvial channels in terms of longitudinal profiles, cross-sections, wood load, grain-size, and indices of stream power; and (ii) spatial and temporal variability of colluvial-alluvial interactions. The third question will be addressed in the context of landscape response to external forcing that cause landslide disturbance, and will exploit data derived from the previous two research components. Overall, this research will be invaluable for understanding environmental impacts of forest practices on mountain streams, drainage basin sediment dynamics, and the influence of landsliding on the evolution of river valleys. In particular, we will be able to document where in the channel network landslide disturbance preferentially occurs and sediment stores, for how long material remains on storage, and the efficiency of fluvial reworking. Last but not least, we expect to improve our understanding on how the structure of drainage basins controls landslide sediment production and interaction with rivers.