A simplified approach for simulating changes in beach habitat due to the combined effects of long-term sea level rise, storm erosion, and nourishment

Abstract

Better understanding of the vulnerability of coastal habitats to sea level rise and major storm events are aided by the use of simulation models. Since coastal habitats also undergo frequent nourishment restoration works in order to maintain their viability, vulnerability models must be able to assess the combined effects of sea level rise, storm surge, and beach nourishment. The Sea Level Affecting Marshes Model (SLAMM) was modified and applied to quantify the changes in the beach area in a 5-km stretch of beach in Santa Rosa Island, Florida due to these combined effects. A new methodology to estimate spatial erosion patterns was developed based on measured erosion during three historic storm events representing a wide range of storm intensities over the study area (named storms Ivan (H5), Dennis (H4), and Katrina (TS)). Future major storms over the 2012-2100 period were generated based on the frequency distribution of historic storms using 4000 simulations to account for uncertainty in the storms temporal distribution. Potential effects of individual, successive, and random storms occurring over the area under 0-1.5 m nourishment schemes were evaluated. The risk of losing the beach habitat in 90 years for different scenarios is studied based on probability distribution contours constructed with the model results. Simulation results suggest that without nourishment, a major storm with a category of tropical storm or higher will reduce the beach at the end of the period by 97-100%. This loss can be reduced to 60% by maintaining a 1-m beach elevation and can further be reduced to 34% with 1.5 m beach nourishment.