Rainfall intensity and catchment size control storm runoff in a gullied blanket peatland
Rainfall intensity and catchment size control storm runoff in a gullied blanket peatland
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DOI：
10.1016/j.jhydrol.2022.127688
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发表时间：
2022-03
影响因子：
6.4
通讯作者：
D. Edokpa;D. Milledge;T. Allott;J. Holden;E. Shuttleworth;M. Kay;A. Johnston;G. Millin-Chalabi;Matt Scott-Campbell;David A Chandler;Jamie L. Freestone;M. Evans
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作者：
D. Edokpa;D. Milledge;T. Allott;J. Holden;E. Shuttleworth;M. Kay;A. Johnston;G. Millin-Chalabi;Matt Scott-Campbell;David A Chandler;Jamie L. Freestone;M. Evans
高地地毯式泥炭在英国集水区的源头广泛存在，但其中大部分已因大气污染、植被变化和侵蚀而退化。这些源头的径流产生是下游洪水风险的一个重要因素，这些地区越来越成为恢复泥炭生态系统和潜在地减轻下游洪水的干预措施的重点。在这里，我们使用一系列多变量分析技术来检查10个地毯式泥炭集水区内部和之间的风暴径流行为控制，这些集水区彼此相距5公里，面积从0.2到3.9公顷不等。研究发现：1)降雨强度是影响流域洪峰大小和洪峰时间的主要因素，总降雨量和前次降雨量仅在小暴雨中对洪峰有重要影响；2)流域间在径流系数、滞后时间、峰值径流及其降雨可预测性方面存在相当大的变异性；然而，3)很大一部分流域间变化可以用流域特征，特别是流域面积来解释；4)对小风暴的峰值流量和径流系数的集水区控制突出了储存和连通性的重要性，而对大风暴的集水区控制则表明地表流量衰减占主导地位。综上所述，这些结果表明了降雨-径流的转换行为，其中集水区储存，连通性和先决条件控制了小的流量峰值，但对更大的风暴变得越来越不相关。我们的研究结果表明，在自然洪水管理潜力的背景下，除了现有的恢复方法之外，扩大洼地储存（例如分布式浅水池）可以增加风暴的范围，其中连通性和储存仍然很重要，对于更大的风暴，以地表径流速度为目标的措施可能很重要。
Upland blanket peat is widespread in the headwaters of UK catchments, but much of it has been degraded through atmospheric pollution, vegetation change and erosion. Runoff generation in these headwaters is an important element of downstream flood risk and these areas are increasingly the focus of interventions to restore the peat ecosystem and to potentially mitigate downstream flooding. Here we use a series of multivariate analysis techniques to examine controls on storm runoff behavior within and between ten blanket peat catchments all within 5 km of one another and ranging in size from 0.2 to 3.9 ha. We find that: 1) for all 10 catchments, rainfall intensity is the dominant driver for both magnitude and timing of peak discharge, and that total and antecedent rainfall is important for peak discharge only in small storms; 2) there is considerable inter-catchment variability in: runoff coefficient, lag time, peak runoff, and their predictability from rainfall; however, 3) a significant fraction of the inter-catchment variability can be explained by catchment characteristics, particularly catchment area; and 4) catchment controls on peak discharge and runoff coefficient for small storms highlight the importance of storage and connectivity while those for large events suggest that surface flow attenuation dominates. Together these results suggest a switching rainfall-runoff behavior where catchment storage, connectivity and antecedent conditions control small discharge peaks but become increasingly irrelevant for larger storms. Our results suggest that, in the context of Natural Flood Management potential, expanding depression storage (e.g. distributed shallow water pools) in addition to existing restoration methods could increase the range of storms within which connectivity and storage remain important and that for larger storms measures which target surface runoff velocities are likely to be important.