Spatial and temporal patterns of off-slope sediment delivery for small catchments subject to shallow landslides within the Waipaoa catchment, New Zealand
Spatial and temporal patterns of off-slope sediment delivery for small catchments subject to shallow landslides within the Waipaoa catchment, New Zealand
复制标题
DOI：
10.1016/j.geomorph.2011.12.037
复制
发表时间：
2012-03
期刊：
影响因子：
3.9
通讯作者：
K. E. Jones;N. Preston
中科院分区：
文献类型：
--
作者：
K. E. Jones;N. Preston
与同等规模的流域相比，新西兰怀帕阿流域是新西兰测量的特定悬浮沉积物产量最高的流域之一。这种沉积物的一个重要来源是浅层滑坡，这些滑坡通常在大规模风暴事件（定义为 72 小时内降雨量约 200 毫米）期间在区域范围内引发。该沉积物级联的第一步是当碎片尾部物理接触并因此被认为是连接时，将滑坡物质从斜坡上清除并进入河流系统。事件中释放的沉积物体积与事件发生后立即留在斜坡上的沉积物体积之间的差值称为斜坡外沉积物输送率。对于 Waipaoa 流域内的小型子流域，该值的范围为 0.12 至 0.28，具体取决于流域形态、山体滑坡和触发事件特征。在Waipaoa 流域，随着子流域面积的增加，流域沉积物输送率下降。可能影响斜坡外沉积物输送的人为过程是风化层耗尽，因为在斜坡下部的先前事件中，由于去除了优选的风化物质，疤痕进一步向上移动。然而，颞部疤痕远离通道的迁移似乎并不普遍。因此，在这种情况下，由于森林砍伐而普遍存在山坡松弛的假设被认为是无效的。相反，沉积物输送比率的时间模式支持了地形事件抵抗模型中因森林砍伐而演变的流域的背景。
The Waipaoa catchment in New Zealand has one of the highest measured specific suspended sediment yields measured in New Zealand compared to basins of comparable size. A significant source of this sediment is from shallow landslides which are often triggered on a regional scale during large magnitude storm events, defined as ~200mm rainfall within 72h. The first step of this sediment cascade is removal of landslide material from the slope and into the fluvial system when the debris tail is in physical contact and hence considered connected. The difference between the volume of sediment liberated in the event and the volume remaining on the slope immediately following the event is termed the off-slope sediment delivery ratio. This value ranged from 0.12 to 0.28 for small sub-catchments within the Waipaoa catchment depending on catchment morphology, landslide and triggering event characteristics. In the Waipaoa catchment a decrease in the catchment sediment delivery ratio is observed as the sub-catchment size increased. A human induced process which may affect off-slope sediment delivery is regolith exhaustion, as scars move further upslope in response to removal of preferred weathered material during previous events on the lower sections of slope. However, it appears that temporal scar migration away from the channels is not prevalent. Therefore, the hypothesis that hillslope relaxation since deforestation is prevalent in this setting is considered null. Rather the temporal pattern to sediment delivery ratios supports the context of evolving catchment in response to deforestation in the Terrain Event Resistance Model.