USGS Coastal and Marine Geology Program

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National Assessment of Coastal Change Hazards


Assessing Hazards along Our Nation's Coasts, understanding and predicting impacts to coastal communities

Coastal areas are essential to our nation's economic, cultural, and environmental health, yet by nature are changing constantly due to a variety of events and processes. Extreme storms can cause dramatic changes to our shorelines in a matter of hours, while sea-level rise can fundamentally change coastal environments over decades. Often, these changes have a devastating impact on developed areas, such as the loss of homes built on retreating cliffs or dunes eroded by hurricane waves. Sometimes changes can be positive, like when new habitat is created by storm deposits. The USGS National Assessment of Coastal Change Hazards (NACCH project) quantifies coastal change hazards along open-ocean coasts in the U.S. and its territories. Coastal communities, emergency managers, and other stakeholders can use the science-based data, tools, models, and other products to enhance coastal resilience.

What is the National Assessment of Coastal Change Hazards?

USGS scientists are working to uncover the ways in which our coasts have changed—and will continue to change—over time. The national assessment has a multifaceted approach that quantifies key factors shaping our shorelines over multiple timescales—some that occur in minutes, others over a century. Scientists examine coastal processes, including extreme storm impacts, long-term erosion, and sea-level rise. Through extensive observation, modeling and prediction of these processes, scientists aim to gauge how U.S. shores have historically shifted, and how past changes will affect their vulnerability to future hazards.

Understanding and Predicting Storm Impacts
Hurricanes, nor'easters, and Pacific winter storms are powerful events that generate dangerous waves and surge capable of moving large amounts of sand, destroying buildings and infrastructure, and even taking lives. Through processes like dune erosion, overwash, and inundation, storms reshape our nation's coastline. The storms component of NACCH focuses on understanding the magnitude and variability of extreme storm impacts on sandy beaches. The overall objective is to improve real-time and scenario-based predictions of coastal change to support management of coastal infrastructure, resources, and safety.

Long-Term Coastal Change
Erosion is a chronic problem along most open-ocean shores of the United States and is an increasing threat to growing coastal populations. As beaches erode—at increasing rates in some areas—there is a demand for accurate information regarding changes in shoreline position. Understanding how the coast has changed in the past and what factors have influenced those changes guides our understanding of what may happen in the future. The USGS has produced a nationally consistent analysis of shoreline position and change along open-ocean sandy shores of the conterminous U.S. and parts of Alaska and Hawaii. These maps provide important information on changes in shoreline position that meet the needs of coastal managers and policy makers.

Understanding Vulnerability to Sea-Level Rise
As our oceans rise, what are today's flood water levels will be tomorrow's high tide lines. The sea-level rise component of NACCH assesses the potential impacts of sea-level rise and provides tools for coastal management decision-making. Historical and recent observations of coastal change are combined with model simulations of beaches, barrier islands, wetlands, and coastal aquifers. By combining observations of coastal change with modeled simulations, USGS scientists determine the probability of coastal change due to sea-level rise and communicate this information to managers who face decisions to avoid, mitigate, or adapt to future hazards.

Coastal Change Hazards Portal
Informed management and policy decisions require expert science as their foundation. The USGS Coastal Change Hazards Portal—an online tool used to interactively "see" past, present and future coastal hazards—can aid in decisions that involve emergency preparedness, ecosystem restoration, and where and how to develop coastal areas. The portal organizes products and information into discrete items within three specific coastal hazard themes: 1) extreme storms, 2) shoreline change, and 3) sea-level rise. The products provided through the CCH portal fulfill critical immediate and ongoing needs for scientifically credible and actionable information to increase resilience to storms and climate change.

Data Integration
As storms continue to impact our coasts and sea levels continue to rise, coastal communities will be faced with difficult decisions regarding coastal development and management practices. The National Assessment of Coastal Change Hazards provides science-based assessments, data and tools about coastal vulnerability to partner agencies, policy makers, and residents to inform strategies for preparing for, mitigating, and responding to our constantly changing coastlines.

About the USGS Coastal Marine Geology Program

USGS Coastal and Marine Geology Program studies coastal and marine resources from coasts and estuaries to the continental shelf and the deep sea, as well as provides expertise, products and tools that address and inform issues shaping our nation.

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Page Last Modified: December 02, 2016 @ 11:23 AM (JSG)