Erosion and deposition for Fanno Creek, Oregon 2012

In 2010, the U.S. Geological Survey (USGS) began investigating the sources and sinks of organic matter in Fanno Creek, a tributary of the Tualatin River, Oregon. Organic matter, more specifically organic carbon, is abundant in Fanno Creek and has been tied to a variety of water-quality concerns. Since organic carbon is commonly found in the fine-grained, organic-rich sediment covering much of the watershed, developing a better understanding of sediment transport dynamics should greatly improve the quality of restoration efforts underway. To address this, a geomorphic approach was adopted, including mapping fine sediment erosion and deposition and measuring changes in sediment. Erosion and deposition mapping within the geomorphic floodplain in the summer of 2012 was used to identify specific sources and sinks of fine sediment and other features that might potentially contribute to the sediment cycle. The distribution of mapped features along Fanno Creek varies by reach. Areas having a high potential for erosion were greatest in the uppermost basin although other middle and lower basin reaches had relatively large areas subject to erosion. Areal deposition is largest in wide, low gradient wetland reaches such as in the middle basin.

2010年，美国地质调查局（U.S. Geological Survey, USGS）启动了针对俄勒冈州图拉丁河（Tualatin River）支流范诺溪（Fanno Creek）内有机质源与汇的调查研究。有机质，更具体而言为有机碳，在范诺溪中含量丰富，且与诸多水质问题存在关联。由于有机碳普遍赋存于覆盖该流域大部分区域的细粒富有机质沉积物中，加深对泥沙输运动力学的认知，将极大提升当前正在推进的修复工作质量。为解决这一问题，研究采用了地貌学方法，包括绘制细粒泥沙的侵蚀与沉积分布图，并测量泥沙的动态变化。2012年夏季，研究人员对地貌河漫滩开展了侵蚀与沉积制图工作，以此识别细粒泥沙的具体源汇以及其他可能对泥沙循环产生潜在影响的特征要素。范诺溪沿线的制图要素分布因河段而异。侵蚀潜力较高的区域主要集中在最上游流域，尽管中、下游其余河段也存在面积相对较大的易侵蚀区域。大面积沉积现象主要出现在宽阔、低坡度的湿地河段，例如中游流域的相关区域。