Abstract
Rising sea levels and growing coastal populations are intensifying interactions at the land-sea interface. To stabilize upland and protect human developments from coastal hazards, landowners commonly emplace hard armoring structures, such as bulkheads and revetments, along estuarine shorelines. The ecological and economic consequences of shoreline armoring have garnered significant attention; however, few studies have examined the extent of hard armoring or identified drivers of hard armoring patterns at the individual landowner level across large geographical areas. This study addresses this knowledge gap by using a fine-scale census of hard armoring along the entire Georgia U.S. estuarine coastline. We develop a parsimonious statistical model that accurately predicts the probability of armoring emplacement at the parcel level based on a set of environmental and socioeconomic variables. Several interacting influences contribute to patterns of shoreline armoring; in particular, shoreline slope and the presence of armoring on a neighboring parcel are strong predictors of armoring. The model also suggests that continued sea level rise and coastal population growth could trigger future increases in armoring, emphasizing the importance of considering dynamic patterns of armoring when evaluating the potential effects of sea level rise. For example, evolving distributions of armoring should be considered in predictions of future salt marsh migration. The modeling approach developed in this study is adaptable to assessing patterns of hard armoring in other regions. With improved understanding of hard armoring distributions, sea level rise response plans can be fully informed to design more efficient scenarios for both urban development and coastal ecosystems.
Highlights
IRIS, School of Environmental, Civil, Agricultural, and Mechanical Engineering, University of Georgia, 0712L Boyd Graduate Research Building, 200 D.W
The costs of adapting to the joint effects of sea level rise (SLR) and storm surge in the United States are estimated to be an undiscounted $990 billion through 2100 under a mid-range climate-sensitivity scenario; the largest share of this projected cost is associated with implementation of hard armoring[35]
Through literature review[37,39,40], application of microeconomic behavioral theory[9,10,44], consideration of the three components of vulnerability, and application of local knowledge based on field reconnaissance and informal elicitation of landowner perspectives, we developed a refined list of socio-economic and environmental attributes that we hypothesized to be associated with the presence or absence of estuarine shoreline hard armoring at the parcel level scale along the Georgia coastline (Table 1)
Summary
IRIS, School of Environmental, Civil, Agricultural, and Mechanical Engineering, University of Georgia, 0712L Boyd Graduate Research Building, 200 D.W. Previous studies have investigated the decision making processes of coastal resident response to SLR by identifying potential drivers of hard armoring at the individual homeowner[37,38,39] and county[40] scales. These studies collectively suggest that contextual and scale-dependent factors are associated with patterns of hard armoring. We assign quantitative representations of these attributes to individual parcels and use a novel, fine-scale census of hard armoring along the Georgia coast to identify individual armored and unarmored parcels; given the abundance of salt and brackish marsh habitats that may be affected by current and future hard armoring emplacement, we solely assess parcels abutting estuarine shoreline. We perform logistic regression analysis to test our hypothesized relationships and examine the power of the socioeconomic and environmental attributes in predicting emplacement of estuarine shoreline hard armoring
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