Paper No. 8
Presentation Time: 1:30 PM-5:30 PM
EVALUATING THE PERFORMANCE OF A RECENTLY NOURISHED ESTUARINE BEACH, THE MISSISSIPPI SOUND, HANCOCK COUNTY, MISSISSIPPI
The renourished beaches in Hancock County, Mississippi have large sections that are classified as erosional hotspots where shoreline retreat rates are on the order of 2-4 m/yr. Hotspots, which are difficult to manage effectively and drastically affect the stability of the beach, often behave differently from the neighboring shoreline and require a more site-specific management approach. Models to explain the cause and predict the behavior of hotspots can contribute solutions to shoreline erosion that are less problematic and environmentally risky. An important driving mechanism of hotspots and shoreline retreat behavior is the distribution of sediment in the nearshore zone by wave-induced currents, which is reflected in the morphodynamics of the nearshore bars. In this study, time-series aerial photographs and beach-nearshore spatial data are used to analyze the relationships between nearshore bar morphologies, wave and tidal current processes, shoreline retreat, and the distribution of sediment in the nearshore zone along a renourished beach in Hancock County, Mississippi. Remote sensing data, GPS shoreline mapping, and shore-perpendicular profiles are utilized to map changes in the shoreline position and the position/orientation as well as the morphology of the nearshore bars. Following the construction of a seawall in the late 1920's the entire shoreline has eroded back to the base of the wall. The nourishment of a 1 km length of beach completed in June 2004 provides the unique opportunity to study the performance of an artificial beach from its inception in an estuarine coastal system. Wave-impacted estuarine beaches are common, but the dynamics of these systems are poorly understood. Mississippi Sound is a low wave-energy, microtidal, fluvially-influenced coastal system dominated by mud-sized sediment. Sand is dominant along the margins of the sound and is primarily sourced from inland Miocene-Pleistocene units and reworked from sandy Pleistocene deposits outcropping along the shore. The prevailing winds are generally from the south-southeast and generate a prevailing westward flowing longshore current. The most energetic wave conditions are associated with the passage of winter cold fronts (20 to 30 per year) or tropical storms. The impact of storms on these beaches is a necessary focus of the study.