Floods and Human Response: Implications for Geomorphic Adjustment and Fish Habitat in the Interior Pacific Northwest

洪水和人类反应：对西北内陆太平洋地貌调整和鱼类栖息地的影响

• 批准号: 0215291
• 负责人: Patricia McDowell
• 金额: --
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0215291&HistoricalAwards=false
• 关键词: Floods; Human; Response; Implications; Geomorphic

Large floods on alluvial rivers produce geomorphic changes that create and renew fish habitat and help regenerate riparian vegetation. Floods renew spawning gravels, scour and deepen pools, and create side channels and other off-channel features. In addition, cottonwoods and other streamside trees important to stream ecology depend on floods for regeneration. All of these features are created during moderate to large flood events. Over a period of years after the flood event they infill, stabilize, or otherwise evolve to a less favorable condition. The goal of this research project is to use evidence from historic large floods to understand the spatial pattern and controls of these geomorphic changes and to determine whether human response to historic floods has limited the ability of rivers to regenerate fish habitat. Many Columbia River tributaries experienced a large flood (a flood the recurs on average once every 50 years or longer) in 1948 or 1965 when flood protection structures (levees, bank stabilization and channelization) were less extensive. They also experienced another large flood in the 1996 when more flood protection structures were in place. Using aerial photos, documentary evidence, and government agency records, spatial patterns of geomorphic change will be analyzed on long continuous river reaches that represent a range of variation in geomorphic controls and flood protection. Geographic information system-based analyses of pre-flood and post-flood conditions will be used to create change maps. Geomorphic change is expected to vary spatially in relation to controls such as valley width, flood power, sediment inputs, inputs of large woody debris. Geomorphic change during the 1996 flood will be examined to determine whether and where habitat creation was reduced by flood protection structures. In addition, historic development of flood protection structures will be reconstructed to see whether or not flood protection structures were built where the greatest flood impacts occurred. If flood protection structures correspond to sites with the highest potential for geomorphic change, the ability of a river to regenerate fish habitat may be severely limited.This project will advance understanding of the spatial controls of flood impacts and understanding of human response to flood damage. The project will also contribute to development of ecologically sensitive flood protection policies. The conflict between flood protection and restoration of aquatic habitat for endangered fish has become acute in the study region. In 1996 a large and damaging flood occurred, and in 1997 more than 20 stocks of salmon in the Columbia River were listed as threatened or endangered under the Endangered Species Act (ESA). Existing flood protection policies are not compatible with the ESA and are currently being revised. Scientific findings like those that will result from this project will inform the debate and decision making by many local authorities throughout the region as they seek to adopt and implement new "fish-friendly" policies. This project will develop ways to identify geomorphic "hotspots" for fish habitat and evaluate whether or not past human response to floods have limited fish habitat. Results of the project will be disseminated through presentations at regional river management workshops and conferences, web pages, and publication in refereed scientific journals.

冲积河流的大洪水产生地貌变化，创造和更新鱼类栖息地，并帮助恢复河岸植被。 洪水更新产卵砾石，冲刷和加深水池，并创造侧通道和其他渠道外的功能。 此外，三角叶杨和其他对河流生态很重要的河边树木也依赖洪水来再生。 所有这些特征都是在中等到大洪水事件期间产生的。 在洪水事件发生后的几年内，它们填充、稳定或以其他方式演变成不太有利的条件。 该研究项目的目标是利用历史性大洪水的证据来了解这些地貌变化的空间格局和控制，并确定人类对历史性洪水的反应是否限制了河流再生鱼类栖息地的能力。 许多哥伦比亚河支流在1948年或1965年经历了一场大洪水（平均每50年或更长时间发生一次的洪水），当时防洪结构（堤坝、河岸稳定和渠化）不太广泛。 1996年，当更多的防洪建筑物就位时，他们又经历了另一次大洪水。 利用航空照片，文献证据和政府机构的记录，地貌变化的空间模式将在长时间连续的河流河段进行分析，这些河流代表了地貌控制和防洪的一系列变化。 将利用基于地理信息系统的洪水前和洪水后情况分析绘制变化图。 地貌变化预计会在空间上有所不同的控制，如山谷宽度，洪水功率，沉积物输入，大型木质残体的输入。 地貌变化在1996年的洪水将进行检查，以确定是否和在哪里栖息地的创造减少了防洪结构。 此外，还将重建防洪建筑物的历史发展，以确定防洪建筑物是否建在洪水影响最大的地方。 如果防洪建筑物对应于最有可能发生地貌变化的地点，河流再生鱼类栖息地的能力可能会受到严重限制。本项目将促进对洪水影响的空间控制的理解，并了解人类对洪水破坏的反应。 该项目还将有助于制定对生态敏感的防洪政策。 防洪与恢复濒危鱼类水生栖息地之间的矛盾在研究区域变得尖锐。 1996年，发生了一场破坏性的大洪水，1997年，哥伦比亚河中的20多个鲑鱼种群被《濒危物种法》列为受威胁或濒危物种。 现有的防洪政策与欧空局不兼容，目前正在修订。 该项目将产生的科学发现将为整个地区许多地方当局的辩论和决策提供信息，因为他们寻求通过和实施新的“鱼类友好”政策。 该项目将研究如何确定鱼类栖息地的地貌“热点”，并评估过去人类对洪水的反应是否限制了鱼类栖息地。 将通过在区域河流管理讲习班和会议上的介绍、网页以及在经评审的科学期刊上发表来传播项目的成果。