Relationships between fluvial aquatic habitat availability and discharge are often assumed to remain static when used with hydrologic datasets to analyze changes in habitat availability over time. Despite this assumption, studies have observed significant changes in aquatic habitat availability before and after restoration projects, dam removals, and extreme flood events. However, research is lacking on how aquatic habitat changes as a result of morphodynamic processes during more commonly occurring hydrologic conditions. This study compared Chinook salmon (Oncorhynchus tshawytscha) rearing habitat availability at 19 discharges before and after a relatively mild 8-year hydrologic period punctuated with modest floods on the lower Yuba River in California, USA. During this time, the total area of rearing habitat remained relatively consistent at discharges <2× bankfull but decreased by up to 25% at discharges >2× bankfull. Significant decreases in rearing habitat area appeared to be the result of widespread erosion on floodplains, terraces, and lateral bars, even after only modest floods. As a result, spatially delineated areas of lost habitat tended to increase in water depth and velocity at baseflow, bankfull, and floodplain-filling discharges, while areas of gained habitat decreased in depth and velocity. Although these specific results may not apply to all rivers around the world, the finding that habitat–discharge relationships change as a result of morphodynamic processes likely does transfer globally and should be considered when making long-term regulatory and management decisions, such as instream flow requirements and habitat restoration plans.

中文翻译：

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由于形态动力学过程，奇努克鲑鱼饲养栖息地-排放关系发生变化

当与水文数据集一起使用以分析栖息地可用性随时间的变化时，河流水生栖息地可用性与排放之间的关系通常被假定为保持静态。尽管有这种假设，但研究观察到水生栖息地可用性在恢复项目、大坝拆除和极端洪水事件前后发生了重大变化。然而，在更常见的水文条件下，水生栖息地如何因形态动力学过程而发生变化，尚缺乏研究。本研究比较了奇努克鲑鱼 ( Oncorhynchus tshawytscha) 在美国加利福尼亚州尤巴河下游经历了一个相对温和的 8 年水文时期之前和之后的 19 次排放时饲养栖息地的可用性，该时期被适度的洪水打断。在此期间，养殖栖息地的总面积在排放量 <2×满岸时保持相对一致，但在排放量 >2×满岸时减少了 25%。养殖栖息地面积的显着减少似乎是泛滥平原、阶地和侧坝广泛侵蚀的结果，即使只是在适度的洪水之后。因此，空间划定的栖息地丧失区域在基流、河岸和洪泛区填充排放时的水深和速度趋于增加，而栖息地获得区域的深度和速度则下降。虽然这些具体结果可能不适用于世界各地的所有河流，