David M. Bush | USGS Science

USGS2011

Comment [on “Sea level rise shown to drive coastal erosion”]

Leatherman et al. [2000] (Eos, Trans., AGU, February 8, 2000, p.55) affirm that global eustatic sea-level rise is driving coastal erosion. Furthermore, they argue that the long-term average rate of shoreline retreat is 150 times the rate of sea-level rise. This rate, they say, is more than a magnitude greater than would be expected from a simple response to sea-level rise through inundation of the shoreline. We agree that sea-level rise is the primary factor causing shoreline retreat in stable coastal areas.This is intuitive. We also believe, however, that the Leatherman et al. [2000] study has greatly underestimated the rate of coastal recession along most low slope shorelines. Slopes along the North Carolina continental shelf/coastal plain approach 10,000:1. To us, this suggests that we should expect rates of shoreline recession 10,000 times the rate of sea-level rise through simple inundation of the shoreline.

Eos, Transactions, American Geophysical Union↗

USGS2001

Coastal-zone hazard maps and recommendations: Eastern Puerto Rico

A series of coastal zone hazard maps cover the area impacted by Hurricane Hugo (1989) in eastern Puerto Rico. The mapping strategy was to develop a tool for quick visualization of multiple hazards for use by coastal planners, managers, property owners, and potential property owners. The Puerto Rico shoreline is heavily developed in places and also highly compartmentalized in terms of shoreline types, geology, and adjacent shelf conditions. Hazards such as coastal erosion, storm surge, riverine flooding, landsliding, and seismic impact also may be compartmentalized. From a management perspective, resources therefore can be allocated on a compartment-by-compartment basis. Six types of hazards were considered in this investigation: (1) shoreline-setting hazards (long-term coastal problems), (2) marine hazards (short-term impacts of coastal storms), (3) earthquake and slope hazards (ground shaking, landslides, and liquefaction), (4) riverine hazards (historical floods), (5) development hazards (high-density development at risk or lowdensity development in extreme-hazard settings), and (6) engineering hazards (special cases in which shoreline engineering projects such as breakwaters or sand mining have significant detrimental effects on portions of the shoreline). Shoreline segments were ranked as being at extreme, high, moderate, or low risk, depending on the number of hazards present within that segment. These rankings are likely to change, gradually over decades with natural coastal evolution, more rapidly as human development infringes on the coastal zone, or in an instant during a severe storm. The hazard maps provide a basis for hazard mitigation and management recommendations.

Puerto Rico↗