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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Bio-geomorphic effects on tidal channel evolution: Impact of vegetation establishment and tidal prism change
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Bio-geomorphic effects on tidal channel evolution: Impact of vegetation establishment and tidal prism change

机译：生物地貌对潮汐通道演变的影响：植被建立和潮汐棱镜变化的影响

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The long-term (10-100years) evolution of tidal channels is generally considered to interact with the bio-geomorphic evolution of the surrounding intertidal platform. Here we studied how the geometric properties of tidal channels (channel drainage density and channel width) change as (1) vegetation establishes on an initially bare intertidal platform and (2) sediment accretion on the intertidal platform leads to a reduction in the tidal prism (i.e. water volume that during a tidal cycle floods to and drains back from the intertidal platform). Based on a time series of aerial photographs and digital elevation models, we derived the channel geometric properties at different time steps during the evolution from an initially low-elevated bare tidal flat towards a high-elevated vegetated marsh. We found that vegetation establishment causes a marked increase in channel drainage density. This is explained as the friction exerted by patches of pioneer vegetation concentrates the flow in between the vegetation patches and promotes there the erosion of channels. Once vegetation has established, continued sediment accretion and tidal prism reduction do not result in significant further changes in channel drainage density and in channel widths. We hypothesize that this is explained by a partitioning of the tidal flow between concentrated channel flow, as long as the vegetation is not submerged, and more homogeneous sheet flow as the vegetation is deeply submerged. Hence, a reduction of the tidal prism due to sediment accretion on the intertidal platform, reduces especially the volume of sheet flow (which does not affect channel geometry), while the concentrated channel flow (i.e. the landscape forming volume of water) is not much affected by the tidal prism reduction.
机译：通常认为，潮汐通道的长期（10-100年）演化与周围潮间带平台的生物地貌演化相互作用。在这里，我们研究了潮汐通道的几何特性（通道排水密度和通道宽度）如何随着（1）在最初裸露的潮间平台上建立植被和（2）潮间平台上的沉积物堆积导致潮汐棱镜减小而变化（例如，在一个潮汐周期中，潮水向潮间带平台倾泻而出的水量）。基于航空照片和数字高程模型的时间序列，我们推导了从最初的低海拔裸露潮汐滩向高海拔的植被沼泽演变过程中不同时间步长处的河道几何特性。我们发现植被的建立导致河道排水密度的显着增加。这可以解释为先驱植被斑块施加的摩擦力使植被斑块之间的流动集中，并在那里促进了河道的侵蚀。一旦植被建立，持续的沉积物积聚和潮汐棱镜的减小不会导致河道排水密度和河道宽度的显着进一步变化。我们假设这是由于潮汐流在集中河道流量之间的分配（只要不淹没植被）和较均匀的表层流（由于植被被淹没）而得到解释。因此，由于潮间带平台上的沉积物增加而导致的潮汐棱镜的减小，特别是减少了板料流量（不影响通道的几何形状），而集中的通道流量（即形成景观的水量）并不多受潮汐棱镜减少的影响。

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