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research >management support >susceptibility analysis >long beach results |
Coastal Susceptibility on the Southern Long Beach Peninsula
A) dune toe and crest elevations, B) annual hours of dune toe impact and dune crest overwash, C) shoreline change prediction, D) susceptibility analysis output mapped on southern Long Beach peninsula orthophoto; asterisks denote significant dune erosion and coastal flooding potential (Voigt, 2000).
Panel A displays the alongshore variability of dune toe and dune crest elevations. The mean dune toe and dune crest elevations for this 8-km stretch of coast measure 4.7-m (NAVD 88) and 7.8-m (NAVD 88), respectively. Beach slope, as calculated between the 1.0 and 3.0-m contours averages 0.025 (1:40). An assessment of the frequency of dune toe impact and wave overwash has been performed utilizing a probabilistic total water level model (Ruggiero et al., 1996), and the results are displayed in Panel B. Although dune overwash is an infrequent occurrence, wave impact at the dune toe is problematic along the southern end of the study area, with 7 locations (denoted by asterisks) experiencing more than 75 hours of wave impact per year. Panel C displays predicted shoreline change for the time period 1995 - 2020 derived from the processes-based shoreline change model UNIBEST (Delft Hydraulics, 1994). Results indicate larger shoreline retreat at the southern end of the case study tapering off to the north. Panel D maps a scenario of potential future impact that reveals several kilometers of shoreline susceptible to coastal change with increased potential for dune erosion and coastal flooding along the southern extent of the case example.
Link to a list of additional readings on science and management integration, technical assistance to coastal communities and analyzing susceptibility to coastal change.
