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Hurricanes and Coastal Storms

Storm warning: Climate change to spawn more hurricanes

Rate of Temperature Change Along World's Coastlines Changed Dramatically Over Past Three Decades

CRMC Policy Relating to Coastal Hazards

The Coastal Resources Management Program (CRMP) has developed regulations for reconstruction after "the big one" as well as other severe storms (Section 180. Emergency Assents). More important are the regulations that are designed to minimize the impact of coastal hazards. Policies regulating where to build on a vulnerable property (Section 140. Setbacks), construction of shoreline protection facilities (various sections), and beneficial reuse of dredged materials help to mitigate some of the hazards associated with coastal living. Sea level rise is a hazard that is only indirectly addressed in the CRMP. Erosion setbacks are very effective regulations that protect the homeowner and the public resources. Much of the Rhode Island shoreline is eroding. Erosion rates are calculated by comparing the shoreline location from historic aerial photographs to the most recent shoreline position. Sections of the south shore barriers have erosion rates of more than three feet per year. That is an average rate over time. In reality, the shoreline may erode tens of feet in a single storm, followed by some accretion. In critical erosion areas on barriers, all residential construction with less than six units must be set back 30 times and commercial property 60 times the average annual erosion rate. The farther the house or commercial structure is setback from the shore, the longer it will last. Unfortunately, these regulations were enacted about thirty years ago. The Council may want to consider policy for when the setback is gone and the structure is on the active beach (figure 1).

House Pilings
Figure 1. House pilings in the wave swash. Old pilings and ISDS exposed after a storm.

Impacts of storm erosion on ISDS are a potential public health problem (figure 2). CRMC worked with RIDEM to develop regulations for repairs to ISDS in critical erosion areas (ISDS Repair Guidance in Critical Erosion Areas, January 31, 2006).

Exposed ISDS
Figure 2. ISDS exposed by storm surge and waves.

Shoreline Protection Structures are prohibited along Type 1 shorelines except where they are used to protect historic structures that are listed on the National Register of Historic Places (Section 220). There are several reasons for this prohibition. The structures reflect wave energy, often causing erosion around the sides of the structure and can cause scouring seaward of the structure. In addition, the structures disrupt sediment transport, both by sequestering sediment that would normally erode from a bank or dune to form new beaches (figure 3), and by physically blocking the sand movement along the shoreline (figure 4). Shoreline protection structures often impact lateral public access along the shoreline. In other words, these structures help protect the property where they are built, but often harm adjacent properties. They are a contributing factor in the narrowing and loss of beaches, and they inhibit the public's right to lateral shoreline access (figure 5). Many of the structures that were built prior to the CRMP cannot withstand moderate storms (figure 6).

Sediment
Figure 3. Sediment that erodes from the headland bluffs forms the beaches. The dotted line marks the extent of the slump block before the sediment was transported by waves and currents.

Aerial Photo
Figure 4. The jetty interrupts the longshore sand transport.

Beach
Figure 5. Lateral access is limited to low tide.

Stones
Figure 6. Many shoreline protection structures cannot withstand moderate storm energy.

CRMC advocates the beneficial reuse of dredged material. The South Coast Habitat Restoration Project is an example of beneficial reuse that has created wider beaches and has the secondary benefit of providing protection for some coastal properties (figure 7).

Scarps
Figure 7. Beach with dredged sand on the left shows no erosional scarp. The beach on the right shows dune scarp and newly exposed ISDS.

Historical Perspective

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Quonochauntaug 1954 & 2004
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Misquamicut 1954 & 2004
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Ninigret Pond in 1954 and Dauphin Island AL during Hurricane Katrina 2005

 

Relevant Sections of the CRMP Dealing with Coastal Hazards

The following lists the relevant sections of the Coastal Resources Management Plan (PDF) dealing with coastal hazards.

Post Storm Actions:
Section 180. Emergency Assents

Pre Storm Mitigation:
Section 140. Setbacks

Section 210.1. Coastal Beaches

Section 210.2. Barrier Islands and Spits

Section 210.4. Coastal Headlands, Bluffs and Cliffs

Section 210.7. Dunes

Section 300.7. Construction of Shoreline Protection Facilities.

Section 300.9. Dredging and Dredged Materials Disposal

Hurricanes

NOAA’s National Hurricane Center (NHC)

Changes in forecast maps and services, including potential storm surge flooding, for the 2014 season that starts June 1 for Atlantic coast (PDF)

Colorado State University Tropical Meteorology Project

Forecast of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2014 (PDF)

"We continue to anticipate a below-average Atlantic hurricane season. While we only expect a weak El Niño to develop this year, conditions in the Atlantic basin appear especially detrimental for hurricane formation. Atlantic Main Development Region sea surface temperatures are cooler than normal, sea level pressures are higher than normal, and vertical wind shear throughout the Atlantic basin has been much stronger than normal. Landfall probabilities for both the United States and Caribbean are below their long-period average values. (as of 31 July 2014)"

Estimated probability (expressed in percent) of one or more landfalling tropical storms (TS), category 1-2 hurricanes (HUR), category 3-4-5 hurricanes, total hurricanes and named storms along the entire U.S. coastline, along the Gulf Coast (Regions 1-4), and along the Florida Peninsula and the East Coast (Regions 5-11) for the remainder of the 2014 Atlantic hurricane season. Probabilities of a tropical storm, hurricane and major hurricane tracking into the Caribbean are also provided. The long-term mean annual probability of one or more landfalling systems during the last 100 years is given in parentheses.

Region

TS

Category 1-2
HUR

Category 3-4-5
HUR

All
HUR

Named
Storms

Entire U.S. (Regions 1-11)

64% (79%)

52% (68%)

38% (52%)

70% (84%)

89% (97%)

Gulf Coast (Regions 1-4)

44% (59%)

30% (42%)

21% (30%)

45% (60%)

69% (83%)

Florida plus East Coast (Regions 5-11)

37% (50%)

31% (44%)

21% (31%)

46% (61%)

66% (81%)

Caribbean (10-20°N, 60-88°W)

67% (82%)

42% (57%)

30% (42%)

59% (75%)

87% (96%)


United States Landfalling Hurricane Probability Project

Probabilities of tropical storm-force, hurricane-force and major hurricane-force winds occurring at specific locations along the U.S. East and Gulf Coasts within a variety of time periods are listed on the forecast team's Landfall Probability Web site. The site provides U.S. landfall probabilities for 11 regions and 205 individual counties along the U.S. coastline from Brownsville, Texas, to Eastport, Maine. Individual state probabilities are also available on this website. The website, available to the public at http://www.e-transit.org/hurricane, is the first publicly accessible Internet tool that adjusts landfall probabilities for regions and counties based on the current climate and its projected effects on the upcoming hurricane season. Klotzbach and Gray update the site regularly with assistance from the GeoGraphics Laboratory at Bridgewater State College in Massachusetts. In addition, probabilities for various islands in the Caribbean and landmasses in Central America are now available on the Landfall Probability Web site.

Relevant Documents

RI CRMC Hurricane Preparedness Guide (PDF)

RI CRMC Rebuilding after the Hurricane (PDF)

RI State Hazard Mitigation Plan (PDF)

RI Flood Awareness & Climate Change Task Force - Rebuilding After a Storm (PDF)

Informational Links

Hurricanes: Science and SocietyMajor goals of Hurricanes: Science and Society are to provide foundational science for understanding complex scientific content, inform visitors about current scientific and technological advances, and to help visitors make good decisions prior to and during a hurricane emergency.

RI Emergency Management Agency:

National Hurricane Center Resources

 

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