White WAMorton RAHolmes CWGeomorphology2010-02-152010-02-152002http://hdl.handle.net/1969.3/2324447-66Submergence of coastal marshes in areas where rates of relative sea-level rise exceed rates of marsh sedimentation, or vertical accretion, is a global problem that requires detailed examination of the principal processes that establish, maintain, and degrade these biologically productive environments. Using a simple super(210)Pb-dating model, we measured sedimentation rates in cores from the Trinity, Lavaca-Navidad, and Nueces bayhead fluvial-deltaic systems in Texas where more than 2000 ha of wetlands have been lost since the 1950s. Long-term average rates of fluvial-deltaic aggradation decrease southwestward from 0.514 plus or minus 0.008 cm year super(-1) in the Trinity, 0.328 plus or minus 0.022 cm year super(-1) in the Lavaca-Navidad, to 0.262 plus or minus 0.034 cm year super(-1) in the Nueces. The relative magnitudes of sedimentation and wetland loss correlate with several parameters that define the differing fluvial-deltaic settings, including size of coastal drainage basin, average annual rainfall, suspended sediment load, thickness of Holocene mud in the valley fill, and rates of relative sea-level rise. There is some evidence that upstream reservoirs have reduced wetland sedimentation rates, which are now about one-half the local rates of relative sea-level rise. The extant conditions indicate that fluvial-deltaic marshes in these valleys will continue to be lost as a result of submergence and erosionACCRETIONComparison studiesDeltasEnvironmentEROSIONMARSHESModel StudiesSEDIMENTATIONSEDIMENTATION RATESedimentation RatesSpatial DistributionSubmergenceSW 0870 Erosion and sedimentationTexasTXUSA,Texas,Lavaca R.USA,Texas,Navidad R.USA,Texas,Nueces R.USA,Texas,Trinity R.Water Level FluctuationsWetlandsJournal