Floodplain connectivity and river corridor complexity: Implications for river restoration and planning for floodplain management.

傳送到

題名:
Floodplain connectivity and river corridor complexity: Implications for river restoration and planning for floodplain management.
著者: Mark Robert. Tompkins
University of California, Berkeley.
主題: Biology, Ecology; Hydrology; Environmental Sciences
所屬期刊: Dissertation Abstracts International 67-08B.
描述: River channels and floodplains are inextricably linked elements of river ecosystems, and hydrologic connections between the two affect geomorphic, ecological, and flood management conditions in river corridors. Many river channels and floodplains have been disconnected, making floodplain ecosystems among the most endangered in the world. Recently, river managers have begun to reconnect floodplains to restore degraded waterways. However, there is still considerable uncertainty associated with planning and design of floodplain reconnection.
To begin to address this uncertainty, I evaluated relationships between floodplain connectivity and river corridor complexity at different scales (i.e., river reach to bedform) and in different settings (i.e., agricultural to urban). I measured changes in river corridor complexity after floodplain disconnection along lower Deer Creek, a tributary to the Sacramento River draining 229 mi2 in Tehama County, California. Using recent and historical aerial photography, I measured decreases in riffle habitat (up to 84%), pool habitat (up to 100%), cumulative channel length (up to 72%), shaded riverine aquatic habitat (up to 81%) and riparian vegetation (up to 94%), and increases in riffle spacing (up to 1162%), pool spacing (up to 178%), and low flow channel width (up to 84%) between 1938 and 1999. These results suggest that significant and persistent reductions in river corridor complexity can be associated with floodplain disconnection, and provide an estimate of restoration potential for floodplain reconnection on lower Deer Creek.
Next, to link changes in complexity to river water temperature dynamics, I measured effects of hyporheic exchange on daily water temperature fluctuations in lower Deer Creek at sites of varying channel complexity. Comparing hourly temperature of upwelling hyporheic water with downwelling water, I observed up to 7.19°C reduction in amplitude of daily temperature fluctuation, up to 3.5°C reduction in daily peak temperature, and lag times between downwelling and upwelling peaks of up to 19 hours. Differences in downwelling and upwelling water temperature characteristics were strongly correlated with elevation difference between downwelling and upwelling sites (R2 = 0.61, 0.53, and 0.69; p < 0.008, 0.016, and 0.003 for amplitude reduction, peak reduction, and lag time, respectively), suggesting that channel simplification related to floodplain disconnection can affect processes occurring at the bar-unit scale.
I also assessed changes in river corridor complexity associated with small-scale floodplain reconnection through post project appraisals (PPAs) of five compound channel projects in the San Francisco Bay Area of California. In most cases, these projects resulted in improved geomorphic and ecological conditions, with width and elevation of created floodplain surfaces (relative to low flow dimensions) apparently the most significant influence on project success. This research builds on previous studies of channel change to develop a new method to measure changes in river corridor complexity associated with floodplain disconnection. In addition, this research adds to recent studies of hyporheic exchange by placing it in the context of river corridor simplification.
This research also provides a systematic assessment of post-project performance of compound channels, an increasingly applied but little studied approach to multi-objective flood management based on floodplain reconnection. Finally, this research proposes a new framework to more effectively put ecosystem restoration on equal footing with flood protection in planning processes for floodplain management.
出版者: Thesis (Ph.D.)--University of California, Berkeley, 2006.
建立日期: 2006
格式: 392 p..
語言: 英文
識別號: ISBN9780542826788
資源來源: NUTN ALEPH

連結

Floodplain connectivity and river corridor complexity: Implications for river restoration and planning for floodplain management.

Mark Robert. Tompkins University of California, Berkeley. 2006

正在檢索遠程資料庫，請稍等