GIS

Army Corps Mitigates Hurricane Impact with GIS

18 Nov, 2009 By: JoAnne Castagna

The Philadelphia and Baltimore Districts use mapping and analysis to help the Northeast prepare for — and recover from — big storms.


The 2009 Atlantic Ocean hurricane season is winding down — it officially ends November 30 — but the U.S. Army Corps of Engineers works year-round to safeguard coastal states in the Northeast from storm events.

The devastating power of big storms was on display in 2003, when Hurricane Isabel's powerful winds and rough waves bombarded the Atlantic Coast. Isabel was the deadliest and costliest hurricane that year, taking the lives of 51 people and costing taxpayers $4.22 billion, according to 2009 figures.

To help protect states in the Northeast, the Army Corps' Philadelphia and Baltimore Districts are relying on GIS — a computer application and tool that enables operators to capture, store, analyze, and display localized information. GIS combines layers of information from various sources, such as aerial photographs and electronic data, to perform analysis. The system produces electronic maps, reports, and charts that agencies like the Army Corps can use to perform missions and solve complex problems.

Reducing Beach Erosion

Hurricane Isabel put New Jersey's shore community in a state of emergency. Along the 125-mile shoreline, Isabel created waves 10 feet higher than normal, killing a surfer and causing flooding and severe beach erosion.

To restore the New Jersey shore and help protect it from future storms, the Philadelphia District is replacing sand along the shoreline. Beach replenishment is a costly process that includes obtaining sand from the ocean offshore using a dredging process and relocating it to the shore.

Beach maintenance projects, such as the replacement of sand displaced during a hurricane, help protect nearby buildings from future storms.

 

To minimize the cost and better manage the sand replenishment work, the district — in collaboration with the State of New Jersey — initiated a study to consolidate its efforts and prioritize sources of sand. In addition, the district created a website using GIS tools, which is helping to make this study a success, said J. Bailey Smith, project manager, Philadelphia District, Army Corps.

"The goal of the New Jersey Alternative Long Term Nourishment Alternative Study is to address New Jersey's beach nourishment issues on a multi-project level rather than on a project-by-project basis," said Smith.

"Planning beach nourishment projects with a system-wide, regional mindset, including the use of GIS, helps to reduce shore protection costs and resources utilized and minimize environmental impacts, as well as helps to identify and critique alternative shore protection strategies for the New Jersey coast," Smith continued.

The New Jersey Regional Sediment Management website was designed to help district personnel share beach nourishment information with each other, as well as with stakeholders and the public. The website comprises an interactive map with layers of data from the study area, overlaid on a base map of the New Jersey coast.

The map of the study area was created using ESRI ArcMap, an application that helps users visualize and organize the data to produce meaningful information about the project. Data sources include aerial photography, bathymetry, and environmental and geotechnical records.

Using ArcGIS Server technology, the map is published to the web, enabling any end user with access to an Internet browser to view the data. The interactive nature of the map helps engineers, scientists, and stakeholders visually review, manage, and analyze the geographically referenced data from multiple perspectives.

 

In addition to the base map, which indicates the New Jersey state boundaries and waterways, users have the option to study additional map layers that show the district's available coastal data, including:

  • Surf clams and fishery data: Project managers are using this information to identify where sea life resides in the ocean. This will determine where they can safely dredge sand without harming sea life.
  • Archaeological data: To help determine where sand can be dredged without damaging historically valuable sites and sea life habitats in the area, project managers use archaeological data to locate shipwrecks and other historical artifacts.
  • Sediment samples: This information helps users identify the properties of sand, such as the size of the grains. Project managers need to know this information so they can match the size of the sand they dredge with what's needed to maintain the shore's environment. This information also indicates how sand is moving along the beaches and inlets on the New Jersey coast.
  • Bathymetry data (ocean depth measurements): Bathymetry helps project managers identify areas of the ocean with potentially large quantities of sand to help prioritize dredging locations.
  • Borrow areas (dredging areas): This information also helps identify consistent, reliable sources of sand.

In these maps, the orange shapes off the coast of New Jersey indicate "borrow areas" — sites off the coast appropriate for dredging up sand for beach restoration projects.

 

The website also provides tools that help users better view the information they need. For example, users can adjust their map views by panning in and out or magnifying, and a measuring tool allows them to determine the actual size of land and water features.

Data from additional Philadelphia District coastal projects will be added to the website in the near future, as it is collected. Historical data will also be converted as needed. The website is already proving to be a valuable resource for the district, its stakeholders, and the public.

Safely Evacuating Residents at Risk

The Army Corps' Baltimore District is using GIS to prepare for evacuation of communities around the Chesapeake Bay, a large body of water located in Maryland and Virginia. Chesapeake Bay was one of the locations hit hardest by Hurricane Isabel. Waves in the bay peaked at eight feet above normal, causing severe flooding that destroyed homes, vehicles, boats, and businesses, and even caused millions of gallons of raw sewage to run into the bay.

If another Isabel were to hit today, the region will be better prepared thanks to work being accomplished by the Baltimore District. With the help of GIS, the district is creating storm surge inundation maps for the Federal Emergency Management Agency's National Hurricane Program (NHP).

Federal partners in the NHP include the Army Corps' Planning Center of Expertise for Coastal Storm Damage Reduction, based at the Army Corps' North Atlantic Division, and the National Oceanic and Atmospheric Administration.

 

By overlaying the flooding maps with population data and aerial photography, community leaders will be able to see what areas may be vulnerable to flooding during different categories of hurricanes. Areas of particular concern include hospitals, fire and police stations, housing units, hotels, emergency shelters, bridges, and roadways. From this information, decision makers can create route maps showing the best roadways for citizens to evacuate, and flooding maps to show citizens whether their homes are in danger of flooding.

Storm surge inundation maps help decision makers understand what areas are at risk and how best to evacuate citizens in the event of a flooding disaster.

 

The storm surge inundation maps are a critical part of the National Hurricane Program, which has a mission to help protect communities and residents from hurricane hazards through various projects and activities. This includes conducting assessments and providing tools and technical assistance to state and local agencies in developing hurricane evacuation plans.

One of these critical tools is the storm surge inundation maps, which — according to Jared Scott, a GIS analyst with the Army Corps' Baltimore District — are bringing hurricane evacuation plans into the twenty-first century.

"In the past, these maps were crafted in multiple ways, including manually calculating and drawing data by hand, and updating these maps took months or even years," said Scott. "With GIS, these maps can be updated instantly with new information and provide quick results, which is important in emergency situations."

The Baltimore District's GIS staff completed worst-case scenario storm surge inundation maps for the State of Maryland (Chesapeake western shore), the District of Columbia, and northern Virginia (counties located along the Potomac River). These maps have proven to be extremely useful for preparedness for a hurricane and other natural disasters.

By applying GIS to hurricane preparedness, the Army Corps isn't just moving evacuation plans into the twenty-first century. The agency is reducing flooding and beach erosion, and saving homes, businesses, and lives.


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