The Mississippi River delta is confined to its course by flood control levees, resulting in a hydraulic isolation and a restriction to the introduction of sediments and nutrients to nearby wetlands. This isolation has resulted in extensive habitat changes in coastal Louisiana including land loss, displacement of freshwater vegetation by salinity tolerant communities, and diminishing fisheries production. As a restoration effort, the State of Louisiana constructed a river diversion at Caernarvon, Louisiana, that introduces river water into the Breton Sound estuary. This estuary was monitored weekly during various discharges for 7 weeks in 2001 and 2002. Water samples were analyzed for total suspended solids, several dissolved nutrients, chlorophyll a and salinity. During high flow (184 m³ s^-1), high nitrate and total suspended sediments concentrations were found over 10 km down the western side of the estuary, but dispersed only within 5 km along the east side. Using the information from the first year, we developed an ecological model that integrated present environmental conditions, mimicked several event pulsing scenarios, such as different river diversion deliveries and hurricane-related tidal intrusions, and evaluated watershed health through long-term scenarios. Results indicated the potential cumulative impacts on Louisiana coastal environments. The water quality values indicated a rapid reduction of nitrite+nitrate and suspended sediment concentrations as diverted Mississippi River water entered the estuary, suggesting near complete assimilation of these constituents by the ecosystem. Model results indicated that any further increases in salinity for any of the sites create deleterious conditions for the marsh communities.