HR: 14:05h
AN: H33J-02    [Abstracts]
TI: Connectivity and Variability as Drivers for Lowland River Backwater Restoration
AU: * SHIELDS, D
EM: DSHIELDS@ARS.USDA.GOV
AF: USDA ARS NATIONAL SEDIMENTATION LABORATORY, PO BOX 1157, OXFORD, MS 38655, United States
AU: KNIGHT, S S
EM: SKNIGHT@ARS.USDA.GOV
AF: USDA ARS NATIONAL SEDIMENTATION LABORATORY, PO BOX 1157, OXFORD, MS 38655, United States
AB: Rehabilitation, protection, and management of floodplain aquatic habitats that are seasonally or periodically connected to the main channel are difficult in landscapes with intensively developed or cultivated floodplains. Here backwater hydrology is often perturbed due to flow regulation by levees or upstream dams, main channel incision, and backwater sedimentation. Additional issues include water quality degradation, aquatic plant infestation, and extreme variation in water temperature and habitat volume during hot, dry months. The pre-rehabilitation status of three severed meander bends along the Coldwater River in northern Mississippi was documented for two years by monitoring the bendways and adjacent river reaches. Backwaters contained up to 2.5 m of recent sediment and experienced near anaerobic conditions with water temperatures greater than 30 deg C during late summer. One of the sites was selected for short-term rehabilitation treatment. An approach for assessing aquatic system status proposed by Kondolf and others (http://www.ecologyandsociety.org/vol11/iss2/art5/) was used to design a rehabilitation project featuring water control structures that trap floodwaters and increase backwater depth and volume. The Kondolf approach evaluates aquatic system status by locating the system in four-dimensional space representing connectivity in the three spatial dimensions and temporal variability. Project design using a simple simulation model and initial ecological responses to rehabilitation are described. The model allows simulation of backwater surface elevation, mean depth and surface area and computes volumes of water exchanged with the main channel for any imposed annual hydrograph with a timestep of 0.0001 day. Backwater control structure (weir) design and operation may be varied to achieve connectivity and variability objectives. Rehabilitation effects on water quality and fish are described.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1813 Eco-hydrology
DE: 1845 Limnology (0458, 4239, 4942)
DE: 1847 Modeling
DE: 1876 Water budgets
SC: Hydrology [H]
MN: 2007 Fall Meeting