Characterizing hydrological connectivity and channel-island processes in river deltas to inform coastal restoration

River deltas are highly dynamic environments that are made up of distributary channels and interdistributary islands. This dissertation uses field observations at the Wax Lake Delta (WLD) and numerical modeling to improve the understanding of hydrological connectivity and coupled channel-island processes in river deltas, and to inform coastal restoration strategies. The studies presented here show that channel-island hydrological connectivity is a key element of delta dynamics. In the first study, acoustic Doppler current profiler measurements show that 23-54% of the water flux entering the WLD channel network is allocated to the interiors of the deltaic islands, indicating that the islands are important elements of the hydrological network. A dye tracer experiment reveals that travel times within the deltaic islands are significantly longer than that of the distributary channels. Based on these observations, a framework for analyzing hydrological connectivity in coastal river deltas is developed. The second study is an investigation of the controls on hydrological connectivity, residence time distributions, and nitrate removal in a river delta channel-island complex using numerical modeling of the hydrodynamics and a simple model for nitrate removal. The modeling results show that channel-island hydrological connectivity and water residence time distributions are strongly controlled by hydraulic roughness due to vegetation within the islands. The modeled fractional nitrate removals range from ~0-87% depending on river discharge, hydraulic roughness, and tidal influences, which compare well with the 47-91% nitrate removal estimated from field data at WLD. In the third study, field measurements and numerical modeling results are used characterize network-scale flow partitioning and water residence time distributions at WLD. The influences of the spring-neap and daily tidal cycles are shown to have a limited influence on the partitioning of discharge through the delta network. Spatial heterogeneity in local water residence times is due to the structure of the delta network and the local channel-island hydrological connectivity. The results from the three studies presented in this dissertation have important implications for understanding the physical controls on hydrological connectivity in river deltas and the management of coastal restoration projects.Civil, Architectural, and Environmental Engineerin