Assess river embankment impact on hydrologic alterations and floodplain vegetation

摘要

For watersheds in arid regions, floodplain vegetation is critically important to maintain the ecosystem health and integrity of the watersheds. Hydrological conditions control the development and evolution of floodplain vegetation and ecosystems in these watersheds. River embankment will alter hydrology of the watersheds and result in floodplain vegetation and ecosystem changes. The present study proposes an approach combining onsite hydrologic monitoring, normalized differential vegetation index (NDVI) remote sensing imagery and GIS buffer analysis to assess river embankment impact on hydrologic alterations and floodplain vegetation. The approach is applied to the Tarim River watershed in China where a recently constructed embankment along both banks of the river provides an ideal study site for assess the impact of river embankment. The changes of shallow groundwater level, NDVI, and land use before and after constructing the embankment are analyzed. The results demonstrate the shallow groundwater levels decrease and groundwater salinity has been greatly increased. With reduced flood risk, more arable land has been established in the floodplain. Thus, natural vegetation generally decreases within 20 km from the embankment, impacted by both human activities and hydrologic alterations. A comprehensive study of floodplain ecosystem composition and structure change will improve our understanding of the impact of the embankment and hydrologic alterations and is warranted in the future.