Wave climate evaluation for Spartina alterniflora existence in coastal Alabama

Salinity, sediment type, elevation, wave climate, and nutrient levels are all important factors influencing the establishment and survival of wetlands, but the initial establishment and survival of a salt marsh is believed to be regulated by wave stress (Knutson et al., 1981; Mitch and Gosselink, 2000). Despite the importance of wave climate, there are currently few methods for its evaluation at wetland locations. Engineers and oceanographers use wave modeling to hindcast and forecast wind-generated wave climate in many different situations. This study used an existing wind-wave hindcast method to estimate wave climate at salt marsh locations. Spartina alterniflora wetland sites were found to have lower wave height levels than nearby eroding wetland and non-wetland sites. These results indicate that wave height frequency distributions based on wind wave modeling hindcasts can be used for wave climate evaluation at wetland locations. Critical wave height levels for salt marsh existence found for the sites in this study of coastal Alabama were H₅₀ = 0.13 m (median H) and H₈₀ = 0.20 m. Sites characterized by non-eroding Spartina alterniflora wetlands had wave climates less severe than these levels. Comparisons between wind-wave hindcasts and two existing wetland wave climate evaluation methods indicated that wind-wave hindcasting is a more consistent method of evaluation.