Anthropogenic inputs of nutrients and sediment are a widespread problem in U.S. streams causing localized impairment and contributing to eutrophication of coastal habitats. Sediments and dissolved nutrients interact through diverse processes including ion exchange, sorption and biotic assimilation by particle-bound bacteria. This study examined the effects of sediment re-suspension on nutrient partitioning in lab microcosms using fine benthic matter collected from two Virginia Coastal Plain streams. Kimages Creek was recently restored following dam removal and was characterized by large deposits of legacy sediments. Courthouse Creek was characterized by sandy substrates typical of Coastal Plain streams. Sediment characteristics differed between the two sites and were influenced by discharge. Net nutrient release rates were similar between streams though reactivity of Courthouse Creek sediments was greater than that of Kimages Creek. Equilibrium Phosphate Concentrations calculated for each site show that fine sediments at Kimages Creek have resulted in higher phosphorus retention potential. Advisors/Committee Members: Paul Bukaveckas.

Regional curves, which relate bankfull discharge and channel geometry (cross-sectional area, width, and mean depth) to drainage area in regions of similar climate, geology, and vegetation, have greatly aided in creating target natural channel designs for stream restoration efforts. Regional curves were developed for peninsular Florida based on cross-sectional and longitudinal survey data collected at 17 gaged and 28 ungaged as near-to-natural streams, ranging in drainage area from 0.2 to 311 square miles and valley slope from 0.02 to 2.27%. Based on an analysis of prevalence among sites, slopes, and hydrologic data, the elevation of the flat floodplain was determined to be the most reliable bankfull indicator at sites with a wetland floodplain, while the elevation of the inflection on the bank was the most reliable indicator at sites with an upland floodplain. Analysis of bankfull indicator slopes further revealed that a water slope threshold of approximately 0.5% exists, above which bankfull indicators appear to more reliable, suggesting that slope-area techniques for calculating the bankfull discharge may be unreliable in peninsular Florida streams with a water slope less than 0.5%. The dataset was further divided based on physiography (flatwoods versus highlands), geography (northern versus southern peninsula), and floodplain types (wetland versus upland and cypress-dominated versus non-cypress-dominated) to determine if significant differences exist in the bankfull regressions and/or various dimensionless ratios (sinuosity, width-to-depth, maximum depth-to-mean depth, valley slope, and maximum discharge-to-mean annual discharge) among various peninsular Florida stream subsets. Streams with wetland floodplains were found to have a significantly greater bankfull area and bankfull width than streams with an upland floodplain. Also, streams with cypress-dominated floodplains had a greater width-to-depth ratio than streams with non-cypress-dominated floodplains. Further, streams draining flatwoods physiographies were found to be flashier. These differences may be important considerations when designing natural channels in peninsular Florida. Annual peak flow data for the gaged sites were analyzed to estimate the bankfull discharge return interval using Log Pearson Type III distributions. The bankfull discharge ranged from less than one year to 1.44 years, which is more frequent than the average 1.5-year return interval often cited in the literature. Based on analysis of the flow duration at gaged sites, bankfull discharge for peninsular Florida streams is equaled or exceeded approximately 21% of the time on average, or about 77 days per year. On average, the bankfull discharge is roughly four times that of the mean annual discharge and is 35% of the 1.5-year discharge. Lastly, the regional curves developed for peninsular Florida were compared to regional curves previously developed for other regions of the southeastern United States Coastal Plain. Peninsular Florida bankfull channels were found to have a lower… Advisors/Committee Members: Wise, William R. (committee chair), Crisman, Thomas L. (committee member).