River floodplains provide critical habitat for a wide range of animal and plant species and reduce phosphorus and nitrogen loads in streams. It has been observed that baseflow‐dominated streams flowing through wetlands are commonly at or near bankfull and overflow their banks much more frequently than other streams. However, there is very little published quantitative support for this observation. The study focuses on a 1‐km reach of Black Earth Creek, a stream in the Midwestern United States (U.S.). We used one‐dimensional hydraulic modeling to estimate bankfull discharge at evenly spaced stream cross sections, and two‐dimensional modeling to quantitate the extent of wetland inundation as a function of discharge. We then used historical streamflow data from two U.S. Geological Survey gaging stations to quantitate the frequency of wetland inundation. For the with‐sediment case, the frequency of overbank conditions at the 38 cross sections in the wetland ranged from 3 to 85 days per year and averaged 43 days per year. Ten percent of the wetland was inundated for an average of 35 days per year. For the without‐sediment case, the frequency of overbank conditions ranged from 2.6 to 48 days per year and averaged 14 days per year. Also, 10% of the wetland was inundated for an average of 25 days per year. These unusually high rates of floodplain inundation are likely due in part to the very low stream gradient and shallow depths of overbank flow.

中文翻译：

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估算流经湿地的以基流为主的河流溢流的频率和程度

河漫滩为各种动植物提供了重要的栖息地，并减少了溪流中的磷和氮负荷。已经观察到，流经湿地的以基流为主的溪流通常在河床满溢处或附近，比其他溪流溢流的频率要高得多。但是，很少有公开的定量支持此观察。该研究的重点是美国中西部的一条小溪Black Earth Creek的1公里范围。我们使用一维水力模型来估算均匀分布的溪流断面的满溢流量，并使用二维模型来量化湿地淹没程度与流量的关系。然后，我们使用了来自两个美国的历史流量数据 地质勘测站量化湿地被淹的频率。对于有沉积物的情况，在湿地的38个断面，高堤条件的发生频率为每年3到85天，平均每年43天。每年平均有35天将百分之十的湿地淹没。对于没有沉积物的情况，高架情况的发生频率为每年2.6至48天，平均每年14天。此外，每年平均有25天将10％的湿地淹没。这些漫长的泛滥平原淹没率可能部分归因于极低的溪流坡度和浅浅的溢流深度。每年平均有35天将百分之十的湿地淹没。对于无沉淀的情况，高架情况的发生频率为每年2.6至48天，平均每年14天。此外，每年平均有25天将10％的湿地淹没。这些漫长的泛滥平原淹没率可能部分归因于极低的溪流坡度和浅浅的溢流深度。每年平均有35天将百分之十的湿地淹没。对于没有沉积物的情况，高架情况的发生频率为每年2.6至48天，平均每年14天。此外，每年平均有25天将10％的湿地淹没。这些漫长的泛滥平原淹没率可能部分归因于极低的溪流坡度和浅浅的溢流深度。