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Human activities have led to the serious decline and degradation of riparian areas in the Southwestern United States. Areas in Arizona, such as the Gila Box Riparian National Conservation Area, are protected to conserve and restore these unique ecosystems. This study investigated temporal change in the channel form and sinuosity of the Gila River in the Gila Box Riparian National Conservation Area. Specifically, cross sections were measured in 1994, 2001, and 2008 to evaluate changes in channel form. Aerial photographs between 1935 and 2007 were also compared to assess changes in channel sinuosity. Based on cross-sectional measurements, the thalweg was significantly deeper in 1994 than in 2001 and 2008, while width-depth ratios were significantly lower in 2008 than in 1994 and 2001. These measurements indicate that the channel is stabilizing. Sinuosity changed only slightly. Overall, climate patterns that cause large flood events appear to have been the major influence on the channel form. Still, exclusion of livestock and all-terrain vehicles, which increased vegetation in the riparian areas, also appeared to mitigate flood impacts. The stream channel appears to have been more resilient to the impacts of the flood in 2005, when vegetation was better established, than to the flood of 1993, when past management influences were still lingering. 相似文献
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Christiane von Reichert John B. Cromartie Ryan O. Arthun 《The Professional geographer》2013,65(1):58-72
Population loss persists in nonmetropolitan America, especially in isolated counties with limited natural amenities. Communities in these counties experience high levels of outmigration among high school graduates, but low in-migration is more important in distinguishing declining from growing nonmetropolitan counties, and return migration is a much more prominent component of in-migration to these locationally disadvantaged areas. This research uses a multisited, interview-based methodology to understand the factors that influence decisions of people in their late twenties to late forties to move back to rural communities and the barriers that keep others from making such moves. The life course segment considered here captures a critical “settling down” period when career and family obligations overlap and return migration peaks. Interviews at high school reunions, the only venues where stayers, return migrants, and nonreturn migrants are found together, show that limited rural employment opportunities are barriers for nonreturnees. Others intent on returning find ways to secure or create employment but are primarily influenced to move home by family concerns. Connections to the larger social and physical environment of the community are important as well. Interviews affirm that factors affecting migration decisions work in combination, and ties to both people and place are critical for understanding rural return migration. 相似文献
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