Browsing by Subject "hydrodynamics"
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Item Factors influencing algal biomass in hydrologically dynamic salt ponds in a subtropical salt marsh(2009-05-15) Miller, Carrie J.The interface between land and water is often a dynamic zone that responds to relatively short-term climatic and hydrologic forces. Coastal salt marshes occupy this zone between land and sea and typically are comprised of vegetated marsh intersected by channels and shallow ponds that are subject to flooding by winds, tides, and storm surges. Coastal salt marshes are widely regarded as zones of high macrophyte productivity. However, microalgae may contribute more to salt marsh productivity than previously realized, underscoring the importance of understanding algal dynamics in such systems. Benthic and planktonic chlorophyll-a (surrogate for total algal biomass), sediment AFDW, total suspended solids, salinity, and nutrients were examined in marsh ponds in the subtropical Guadalupe Estuary, TX, USA to determine the effects of hydrologic connections on algal biomass in this system. From May 2005 ? May 2006 there were several pond connection, disconnection, and desiccation events. During periods of disconnection, algal biomass was higher in both the benthos and the water column than during connection events when supposed flushing occurred. Connection events also flushed out high NH4 accumulating in pond surface waters, but did not increase NOx. Therefore, the primary source of DIN seemed to be nutrient cycling within the ponds. There was a temporal effect on surface water salinity, which increased throughout the sampling period as bay water levels and subsequent pond connections decreased, demonstrating interannual variability and the link between seasons (wet vs. dry) and marsh inundation patterns (high water periods vs. low water periods) in this estuary.Item Hydrodynamics and sediment transport in natural and beneficial use marshes(Texas A&M University, 2006-10-30) Kushwaha, VaishaliSince 1970, U.S. Army Corps of Engineers, Galveston District, has been using dredged sediments from the Houston ship channel to create and restore salt marshes in Galveston Bay. Some projects have failed due to excessive sediment erosion or siltation. The research reported here applies an engineering approach to analysis of tidal creeks in natural and beneficial use marshes of Galveston Bay. The hydrodynamic numerical model, DYNLET, was used to assess circulation in marsh channels. A preliminary sediment transport model was developed to analyze erosion and deposition for the same channels. In situ flume experiments were conducted to determine the sediment erodibility in natural and constructed marshes. A natural reference marsh, Elm Grove, was studied to understand marsh hydrodynamics and model calibration. The model results show that DYNLET can largely duplicate the marsh hydrodynamics and the sediment transport model can provide preliminary indication of erosion in tidal creeks. Analysis of the preliminary channel layout of the beneficial-use marsh demonstrated that channels will have sufficient circulation and optimum velocities.