Reports & Toolkits

Local Government Guide to Coastal Management: The Basics

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Coastal Hazards

A broad range of natural hazards affect coastal communities on the Gulf of Mexico, ranging from coastal storms and shoreline erosion to harmful algal blooms and sea level rise. These hazards are often in tandem and cascading. For instance, coastal storms, including tropical storms and hurricanes, cause damage both through flooding and damaging winds.

Flooding

Flooding is the costliest and most common natural hazard to occur in the United States. Flood hazards are expected to become more severe in the Gulf of Mexico as severe coastal storms become more frequent and sea levels rise.

Riverine flooding

Riverine flooding is the flooding caused by too much rain. Any storm that produces more rain in a short period of time than the natural and man-made landscape can accommodate will lead to flooding, as water fills and overflows the natural banks of rivers, lakes, wetlands, and manmade flood control devices such as levees. The more rainfall experienced across a watershed during a storm, and the longer a storm lingers over the watershed, the more severe riverine flooding can be.

High-tide flooding

Also called nuisance flooding, high-tide flooding23 is low-flood-level, periodic flooding caused as high tides creep higher than stormwater systems, shorelines, and built structures were designed to accommodate. It is often characterized by seawater backing up through storm drains. High tide flooding can damage basements, block roads, and accelerate the deterioration of structures and public infrastructure. It harms vegetation, which can destabilize vegetation-stabilized slopes and degrade natural ecosystems. And it amplifies erosion problems. These impacts, especially when recurring over time, drag down local economies by decreasing access to commerce, inconveniencing residents, workers, and visitors, and increasing maintenance costs.

Storm surge

Storm surge is a rise in the level of the seawater during landfall of a coastal storm, caused primarily by the storm’s winds pushing water onshore. Coastal flooding caused by this effect is often measured as storm tide, the total observed seawater level during a storm, adding together the excess height of storm surge above normal tide levels. Storm surge is made more severe by how intense the storm’s winds are and by the point in the tidal cycle (high or low tide) when the storm makes landfall.

Impact of flooding on coastal communities

  • Human injury and death
  • Damage to structures and infrastructure
  • Power loss
  • Damage to building contents and crops
  • Deposition of debris and sediment
  • Erosion/scouring of shorelines
  • Blocking roads, impeding evacuation and rescue efforts
  • Public health impacts from waterborne disease and toxins
  • Degradation of natural systems
  • Immediate business disruption and loss of livelihood
  • Long-term dampening in economic growth

The severity of flood impacts on an individual structure depends on the depth, velocity, debris load and duration of floodwaters. The duration of inundation depends on the capacity of the watershed system to flush the excess water out to sea quickly. The severity of flood impacts across a community also depends on broader factors like the degree of development in hazard-exposed areas and the availability of necessary resources for recovery.

Return period

Also called the recurrence interval, the return period is a way of expressing how likely a flood of a given severity is on average, based on historical data about past floods in a given area. A “100-year flood” is a flood level with a 1% likelihood of occurring at least once in any given year, based on historical averages. The term can be misleading, because it does not mean that a 100-year flood probably won’t happen again for 100 years after the last 100-year flood. Any home in a 100-year floodplain has a 26% chance of experiencing a flood during a 30-year mortgage period, regardless of if and when it has flooded before. Return periods also do not account for future changes, such as sea level rise or changes in the watershed’s ability to drain floodwaters.20

Flood control systems

Well-maintained flood control systems, such as storm drains and pumps, and well-functioning natural systems, such as healthy wetlands and open space, can decrease the severity, duration, and impacts of flooding by preventing more water from getting in during the storm, and by flushing it out more quickly after the storm. Impervious surfaces like roads and buildings, which prevent water from recharging into the ground, and failing flood control systems can increase the severity of flooding impacts.

Flood insurance

Flood hazards have primarily been insured by the federal government over the past half century. FEMA provides flood insurance to residential property owners and certain commercial property owners through the National Flood Insurance Program. This difference in insurance providers can cause confusion for home-owners – in the past, flood-impacted homeowners have been caught off guard, thinking that their homeowners insurance policy covered flooding when it did not. There has been increased interest in the past few years from the private insurance industry to offer new, separate flood insurance products; however, it is still standard for flooding to be excluded from homeowners insurance policies.

Damaging Winds

Wind hazards, including sustained and high winds as well as tornadoes, can be brought about by coastal storms such as tropical storms and hurricanes, as well as by severe inland storms. Wind loads and windborne debris, especially falling trees and tree limbs, are both capable of damaging structures.

Hurricane winds

Hurricanes can generate sustained winds ranging from 74 mph (Category 1) to greater than 155 mph (Category 5) over durations of 12 to 24 hours. The National Weather Service uses the Saffir-Simpson Hurricane Scale to rate hurricanes according to the potential of the storm winds to cause damage. Hurricane wind damage covers wide areas. Modern hurricane forecasting technologies and techniques allow the NWS to provide generally reliable warning of likely exposed communities with 3-5 days’ notice. The magnitude of a storm upon landfall cannot be as reliably forecast.

It is important to note that the Saffir-Simpson Scale does not measure the likely magnitude of flood damage by a storm. Hurricane Andrew, which made landfall on Florida as a Category 5 hurricane in 1992, was an example of a storm which caused catastrophic damage primarily through high winds, while Hurricane Katrina, which made landfall on Louisiana and Mississippi as a Category 3 hurricane, caused devastating damage primarily through flooding.21

Tornadoes

Tornadoes are most common between March and August, but they can occur at any time. Although tornadoes can occur anywhere in the United States, the frequency and intensity of tornadoes varies greatly. For example, as a result of almost daily and relatively weak thunderstorms, Florida has a disproportionately high frequency of weaker tornadoes in the EF0 to EF2 range. The non-coastal regions of Alabama and Mississippi and the Southern Plains States of the central U.S. (a.k.a. “Tornado Alley”) have a disproportionately higher frequency of intense thunderstorms, and thus stronger tornadoes in the EF3 to EF5 range. Tornado damage is typically confined to the path of the tornado itself, but with the most severe tornadoes that path can be broad. Tornadoes cannot be precisely forecasted, so tornado-exposed areas must prepare shelter ahead of any potentially tornadic storm.22

Tornado intensity is classified using the “Enhanced Fujita” (EF) scale, a method to rate tornado intensity based on the degree of structural damage to be found when investingating an affected area after a storm.

EF Number 3 Second Gust (mph)

0 65-85

1 86-110

2 111-135

3 136-165

4 166-200

5 Over 200

Erosion

Areas of erosion and deposition along the coast are a natural part of coastal dynamics, including beaches, cliffs, and rivers. Sediment naturally flows through these dynamic systems, changing their shape over time. These natural pressures of change work at odds with human development and property lines that are designed to remain static. Erosion undermines buildings, roads, and utilities, eventually rendering them unusable, and brings the shoreline closer to other structures, increasing their exposure to flood hazards. Erosion also destroys wetlands and undermine dune systems that are critical for flood hazard protection and ecosystem health

Gradual vs. Rapid

Erosion can happen gradually, but most coastal erosion occurs in an episodic pattern, with a low background erosion rate punctuated by major storms that significantly change the shape of the coastline, creating a higher average erosion rate over time. As sea level rises, erosion rates change, often rising.

 

Under common law, land that erodes gradually is considered removed from the property owner’s land (just as land that accretes gradually is considered added), but land that erodes rapidly, like during a storm, is considered to remain part of the property. Different state laws and practices modify this principle, affecting the responsibilities and authorities of counties and municipalities to protect and manage changing shorefronts.

Harmful Algal Blooms

Harmful algal blooms, or HABs, occur when colonies of algae—microscopic waterborne plants—grow out of control while producing toxic or harmful effects on people, fish, shellfish, marine mammals, and birds.

Causes of HABs

A range of events can cause HABs, including particular wind and current conditions, coastal storm impacts, and changes in nutrient levels in the water system. They can be made more severe by pollution, including nutrients like nitrogen, phosphorus, and carbon, running off into watersheds, spiking the population of algae species well above what is normally present in the water.

Impacts of HABs on coastal comm

People often get sick by eating shellfish containing toxins produced by these algae. Airborne HAB toxins may also cause breathing problems and, in some cases, trigger asthma attacks in susceptible individuals. HABs are a serious regional and national economic concern because they affect not only the health of people and marine ecosystems, but also the strength of local economies that depend on affected beaches, waterbodies, and wetlands. HABs reduce tourism, close beaches and shellfish beds, and decrease the catch from both recreational and commercial fisheries.

Sea Level Rise (SLR)

The water level reached by high tides on a daily basis in coastal communities is determined by the combined influence of several global and local factors. When planning for future sea level rise, it is important to remember that these changes will have serious negative impacts on the community decades before a given parcel or neighborhood is permanently underwater.

Global SLR

Globally, sea levels have been rising over the past century, and the rate of global sea level rise has been increasing in recent decades.

Relative SLR

Regionally, variations in currents and ocean dynamics can make sea level rise rates vary from the global average. Also, while the ocean is changing, the land continues to change underneath it – in much of the Gulf Coast, land subsidence caused by compacting sediments, changes in groundwater, and long-term changes in the shape of the Earth’s crust serves to magnify the local effect of rising sea levels. These regional variations make the rate of local sea level rise, called relative sea level rise, the most important factor to understand to plan for this hazard.

 

High rates of subsidence and global sea level rise have combined in areas of the Gulf Coast to create some of the highest rates of relative sea level rise in the United States.

Saltwater intrusion

Groundwater aquifers provide drinkable water for domestic use, agriculture, and industry. Groundwater flows outward at the coast, pushing back salt water from contaminating these aquifers at a transition zone.24 Sea-level rise can increase saltwater intrusion into groundwater aquifers, pushing the fresh/saline transition zone inland. This encroachment may be further exacerbated by increased groundwater pumping from increasing development density along the coast and drought, by reducing the supply of freshwater flowing outward against the saltwater. Saltwater intrusion into groundwater aquifers can increase treatment costs for drinking water facilities or render groundwater wells unusable.

Other impacts of SLR

Sea level rise can accelerate coastal erosion, degrade and incapacitate stormwater systems that were not designed for future sea levels, and destroy wetlands that are critical for sustaining economically significant ecosystems and mitigating flood impacts.

Natural and Cultural Resources At Risk

Natural resources are considered “materials or substances such as minerals, forests, water, and fertile land that occur in nature and can be used for economic gain.” In the case of the Gulf, seafood, oil, and gas are among the primary natural resources, but they have also shaped the culture, traditions and history of the region. Cultural resources are an often overlooked but essential attribute of any community. Cultural resources are associated with the history and traditions of a place, both past and present. More difficult to define, these may be landmarks such as historic buildings, but also less tangible things like music, culinary styles, and oral histories. This section briefly summarizes each of the biggest industries in the Gulf of Mexico and the economic benefits they provide to the region, which amount to approximately $234 billion each year.9

Commercial Fishing

Commercial fishing in the Gulf of Mexico is a multi-billion dollar industry that harvests fin fish, shrimp, oysters and crab. Gulf Coast residents are employed in the commercial fishing industry in many capacities: operating fishing vessels, maintaining gear, sorting and packing catch, and so on. It is clear that the livelihoods of thousands of people rely on the continued availability of seafood for commercial use.

Hurricanes and other extreme weather events can be exceedingly detrimental to marine life. Flooding and intense wind can push pollutants and debris from the land out into coastal waters. Furthermore, storms can damage oil infrastructure which results in leaks and spills that can devastate marine populations in both the short and long term. Years following oil spills, research shows that marine life have issues ranging from contaminated eggs, impaired reproduction and altered blood chemistry. Therefore, this immense industry relies heavily on adequate preparation for and recovery from disasters.

The table below describes the economic impact of commercial fisheries in the Gulf of Mexico broken down by state12:

Shipping

The Gulf of Mexico, including the prominent Mississippi River delta, is a key trading region for imported and exported goods in the United States. As of 2016, over half of the top 25 US ports by total tonnage were located in the Gulf, including the top 2 -- South Louisiana, LA and Houston, TX. -- source is the NOAA GOM Second Look document, accessed 9/21). They service 213 million tons and 211 million tons a year, respectively. In fact, the South Louisiana port is the largest tonnage port in the entire Western hemisphere!

In addition to the port cities themselves, the Gulf also is home to the Gulf Intracoastal Waterway; this is a 1300 mile man-made canal along the Gulf of Mexico from Texas to Florida. The Texas stretch of this canal alone handles up to 90 million tons of freight annually.13

The primary commodities that pass through the Gulf of Mexico are crude petroleum, petroleum products, chemicals, and food:

Chart of XXX

There is reason to believe that shipping patterns may be impacted by climate change. Increased precipitation could cause the build up of silt and debris in some areas, narrowing channels and restricting access. Port infrastructure can be subject to damage from high winds associated with tropical storms and hurricanes. In the 2014 National Climate Assessment, the Gulf Coast was identified as particularly vulnerable to these effects.

Economic benefits:

Marine transportation, including deep sea freight, navigation equipment, and warehousing is an essential aspect of coastal life in terms of local employment and gross domestic product. In 2009, fifty percent of all US international trade tonnage passed through the Gulf coast ports. This industry accounts for a significant number of jobs and percentage of ocean based economy, particularly in Texas, Louisiana, and Florida. In Florida alone, over 60,000 jobs are related to the marine transportation industry; this amounts to $8.4 billion of the national GDP. Severe storms can not only damage vessels, but can impact the ease of travel in man made canals. Continued maintenance and sustainable design of seafaring vessels as well as the channels in which they travel is essential to preserving this valued activity.14

Oil and gas

Chief among industries in the Gulf Coast is the production of oil and natural gas. There are approximately 3700 active oil and gas platforms in the Gulf of Mexico, producing about half of the entire oil, gas, and refined oil in the US every year. Both platforms and pipelines are pervasive throughout the region.

Extreme weather can be devastating for oil and gas infrastructure. Hurricane Harvey shut down 22 percent of the nation’s refining capacity and led to the leakage of millions of pounds of air pollutants into Texas communities.15 Offshore production, which is administered by the federal government, is a growing component of domestic oil production and is particularly vulnerable to extreme weather. Hurricanes Katrina and Rita destroyed more than 100 oil platforms and damaged 558 pipelines. This is not only a serious economic disruption, but spills also threaten the health of the entire marine community. Currently, the US offshore, particularly the Gulf of Mexico, produces 30% of US oil and 10% of US natural gas.16

Economic benefits:

Oil and gas are incredibly valuable to the United States economy, and the Gulf of Mexico provides about half of that value. Oil and gas not only supply the nation with an energy source, but also supply the region with jobs. The total wages earned by those working in the oil and gas industry in the Gulf Coast in 2009 was $15.6 billion. Across the entire Gulf Coast, the oil and gas industry employs 2.7 million people, equivalent to 12.2% of the jobs in Texas, 11% of the jobs in Louisiana, 5.3% of the jobs in Mississippi, and 3.4% in Alabama.17

Offshore production plays an important role here as well. In 2009, offshore production alone in the Gulf of Mexico generated almost $70 billion of economic value and 400,000 jobs.18

Tourism

The Gulf Coast not only supports huge national industries, but provides the opportunity for ample recreational activities with its warm climate, beaches, and abundant wildlife. Some of the most popular tourist activities include:

  • Recreational and charter boat fishing

  • Water sports and swimming

  • Restaurants and bars

  • Wildlife viewing

 

Even birds can be a real attraction for those visiting the Gulf.  In 2006, more than 7 million people participated in bird watching in eastern Florida and the Gulf region. Wildlife watchers in this region spent nearly $7 billion on related goods and services, such as equipment purchases like binoculars and cameras.

 

Economic benefits:

Much like oil, many of the Gulf region’s residents rely on tourism for their livelihoods. 8% of jobs in the Gulf Coast Region are in the tourism and recreation industry. The total employment and wages associated with tourism in the Gulf can be found in the table below:

If coastal communities are under the threat of hazards, their viability as tourist destinations may be severely limited.

Ecosystem Services

In addition to fisheries and tourism, the natural features of the Gulf of Mexico provide many other tangible benefits. Chief among these are the presence of healthy wetlands and oyster reefs for water quality, soil erosion control, and storm protection. As these habitats are destroyed and developed, their ability to provide a wide protective barrier for the human structures inland is severely compromised. Furthermore, these habitats are essential to the commercial fisheries industry, as 97% of commercial fish and shellfish are species that depend on them for at least some portions of their life cycle.

 

Louisiana has 40% of the wetlands in the US. However, if current rates hold, one third of Louisiana’s coastal wetlands will be lost by the year 2050. Wetlands across the Gulf are quickly being converted to open water, bare land, agriculture, and urban development. 272 square miles of wetlands were converted in the Gulf of Mexico coastal watershed area from 1996 to 2006. Preservation of these features is not only essential to the health of flora and fauna, but to the wellbeing of human communities.

 

Economic benefits:

The natural habitat of the Gulf is not only beautiful and a source of pride, but the ecosystem services it provides also translate into actual financial savings. Whereas man made water treatment systems can be costly, preserving the existing landscape can yield comparable results. New York City found that it could avoid spending between $3 and 8 billion on new treatment plants by investing in purchasing and preserving the native landscape in the state. It is estimated that coastal wetlands provide the United states with $23.2 billion in storm protection annually.19 This amount does not even include the ample financial benefit gained because these habitats support the growth and development of commercially harvested marine life, as described previously.

Mitigation

According to FEMA, “hazard mitigation is any action taken to reduce or eliminate long term risk to people and property from natural disasters.”25 This definition acknowledges that flood events will occur, but that their consequences can be made less severe, on short and long term scales, with adequate preparation before, during and after the event. This section briefly describe some basic techniques and strategies at the disposal of local governments.

Structural

Structural flood reduction measures include the addition of new levees, dams, and other built protections, as well as the retrofitting, or facility hardening, of already existing structures. Retrofitting is the addition of resilient design elements to improve a facility’s ability to withstand all-hazard events. Existing structures should be evaluated for their adaptive capacity, or how easily they could be modified to improve resilience.

Grey infrastructure

Grey Infrastructure refers to man-made infrastructure, such as levees, roadways and drainage pipes. It is made of cement and asphalt, which prevent water from soaking into the soil and allow huge volumes of fast-moving storm water to ow directly into streams.

Green infrastructure

Green infrastructure is the integration of natural features and natural stormwater management principles into the built environment. It uses vegetation, soils, and natural processes to create healthier environments. Examples may include bioswales, rain gardens, green roofs, and so on.

Preservation and restoration

As previously described, many natural features that can mitigate the effects of floods already exist within the coastal landscape. Coastal projects to preserve and restore these features can help mitigate against coastal erosion, wind damage and flooding associated with storms and sea level rise. The benefits associated with the types of projects listed below include physical benefits, such as reduced impacts of flooding, storm surge, and wind damage, improved water quality, and enhanced biodiversity of coastal areas, as well as social and economic benefits, such as property, lives, and infrastructure saved.

For more detailed information about restoration techniques, refer to the “Geography of the Gulf of Mexico” section.

It is important to remember that protecting individual buildings is essential, but must be done in conjunction with other, broader strategies. If, for example, a home is floodproofed, those residents may still be in peril if the roads surrounding the home are impassible and they are isolated from emergency supplies and staff.

Specific Strategies:

Building elevation

New and existing buildings can potentially be raised above the flood level. This option may be less costly than moving the building entirely, and is less disruptive to the neighborhood. Buildings can be raised on earthen fill, on piers, or on foundation walls that create an enclosed space beneath the building

Flood barriers

Using dirt, soil, concrete, or steel, a barrier can be built around buildings to stop flood waters from entering the property. However, this option may be prohibited if it exacerbates flooding or drainage problems elsewhere.

Dry floodproofing

All areas of a building that are below flood elevation may be made watertight, as to limit the amount of water that can penetrate the exterior and cause damage inside. This may require the removal of windows and vents, which is not feasible for all structures.

Wet floodproofing

In some cases, it may be more appropriate to allow flood water into parts of a building where valuable and vulnerable contents have been placed elsewhere. This may include placing electrical equipment, laundry facilities, and other utilities permanently on a higher floor of a building. This can be a cost effective option for existing structures.

Non-structural

Non-structural flood reduction measures focus on managing human behavior and enforcing policies that increase resilience and adaptability to disasters. These options include acquisition of flood prone structures, certain building guidelines such as wet and dry floodproofing, and the development of thorough emergency evacuation plans far in advance of an event.

Planning and zoning

Planning and zoning can prevent the development of sensitive structures in vulnerable areas to begin with. For example, a local government may zone floodplains for open space preservation. Local planners and officials may push for requirements of stormwater capture on newly developed properties (in other words, on-site compensatory storage) or a limit on impervious surfacing. They may also require an engineering study to evaluate stormwater impacts of new development projects.

Buyouts

Flood buyout, or property acquisition, programs enable local governments to purchase eligible homes prone to frequent flooding from willing, voluntary owners and return the land to open space, wetlands, rain gardens or greenways. Properties are prioritized for buyout based on their flood risk and the mitigation benefits to the community, including millions of dollars in savings from averted damages.

Public Education and Awareness

Clear communication with residents of a community can be exceedingly helpful in ensuring fast and efficient recovery after a coastal hazard event. Furthermore, members of the public may have anecdotal information about flood frequency and historic events that can supplement other tech based approaches, such as Lidar or GIS.

 

For more information about effective communication strategies, please refer to the “Communicating Risk” section.

Multi-jurisdictional and cross-departmental collaboration

Many partners are involved in mitigating the effects of coastal hazards. Coordinating efforts and plans between local and regional planners, public works, local officials, engineers and emergency services, such as police and fire, is an essential and sometimes overlooked step. Comprehensive plans should be made at the neighborhood level for how residents will be evacuated and rescued in the event of a disaster. County officials should meet with planners and emergency services staff before an event occurs to ensure that their priorities are all aligned and responsible parties have been identified for pre, during and post disaster efforts.

 

For more information about developing response plans, refer to ASFPM’s No Adverse Impact Toolkit, Chapter 7, Emergency Services.25 For more information about partnerships, see the “Partnerships” section below.

The Association of State Floodplain Managers’ No Adverse Impact (NAI) Toolkit may be a useful resource to learn about more potential strategies.

Partnerships

When confronting coastal hazards, partnerships are critical for access to necessary information, expertise, insights, funding, data, tools, and resources. Sometimes partnering on coastal hazards implies working within existing relationships, such as mutual aid agreements, to identify and coordinate on common priorities. In other cases, it involves reaching out to new partners. A range of resources exist at the state, federal, and non-profit sectors to promote hazard resilience.

County and local

Multi-jurisdictional partnerships provide an opportunity for local and county governments to coordinate resources, plan on an ecosystem-wide basis, and achieve mitigation efforts collectively that would be impractical with a single community’s capacity.

State

Key state partners include:

  • State hazard mitigation and floodplain management officials are responsible for implementing hazard mitigation and floodplain management plans statewide, and can provide guidance, technical assistance, and hazard data.
  • Coastal zone management programs provide funding, data, planning assistance, and technical capacity to identify, plan for, and mitigate coastal hazards.
  • National estuarine research reserves provide long-term research, environmental monitoring, education, and stewardship of coastal natural resources, and can provide training and support through the Coastal Training Program.

Federal

Key federal partners include:

  • FEMA provides funding for pre-disaster mitigation and post-disaster recovery, technical assistance, guidance, and resources for identifying, measuring, comprehensively planning for, and mitigation hazards. FEMA operates the Community Rating System (CRS), which rewards communities for managing flood risk, and offers technical assistance.
  • USACE conducts comprehensive studies and plans for flood risk, and can construct structural flood control measures. USACE also provides funding and assistance for communities undertaking non-structural flood control measures.

Non-profit

Potential non-profit partners include:

  • Academia can provide data and technical assistance

 

Funding

To come

 

Geography of the Gulf of Mexico

The Gulf of Mexico is a region known for its great diversity of habitat types, both marine and terrestrial. The U.S. portion of the Gulf of Mexico region extends from the Florida Keys westward to the southern tip of Texas, following the 47,000 miles of coastline of the five Gulf Coast states1: Florida, Alabama, Mississippi, Louisiana and Texas. Explore below to learn more about the coastal habitats of the region and how the preservation and restoration of each can improve local resilience:

Coastal wetlands

Wetlands, whether coastal or inland, represent portions of land that can slow the advance of storm surge by dissipating wave energy and temporarily sequestering runoff during high precipitation events.2 This process may aid in mitigating natural hazards and enhancing coastal resiliency. The wetlands along the Gulf of Mexico cover approximately 5 million acres.

Wetland restoration typically involves reintroducing and retaining water to a degraded or drained wetland site. If you are in a county that has turned wetland area into agricultural area, the most common, economical, and often simplest restoration technique involves removing a section of drainage tile (typically found under agricultural land). Restoration techniques may also involve marsh terracing, or or mechanical excavation and filling which involve creating new marsh area by recycling marsh sediment from other areas of the ecosystem to a new site and planting marsh vegetation in this newly created or restored sediment area.

Mangrove forests

Mangroves - a type of coastal wetland - are shrub and tree species that are resilient to saltwater and can therefore live along shores and estuaries in the tropics and subtropics. Four species of mangroves exist in the United States.3 These plants have distinctive arched root systems that grow in and out of the soil, stabilizing the earth and also providing a windbreak and wave break to shelter inland areas from tropical storm gusts and flooding. These coastal forests also serve as nurseries for many species of fish and mollusks. One study showed that there were 25 times more fish found on reefs close to mangroves as compared to reefs near mangroves that had been cut down.4

Oyster reefs

One of the most iconic creatures of the Gulf is the small, yet commercially and environmental vital, oyster. Oysters settle onto solid surfaces such as piers, rocks, and each other to develop. Over time, these piles of oysters growing together become a reef. Oyster reefs are valuable not only as a harvested commodity, but also for providing a safe nursery for species including shrimp, crabs, anchovies, and a variety of finned fishes, and for filtering the water surrounding them of toxins and pollutants. A single oyster filters up to 50 gallons of water per day!5  Like mangrove forests, oyster reefs also serve as a protective barrier for the wind and waves associated with storms. Oyster populations are also at historic lows, due to nutrient pollution, unsustainable harvesting practices, and development. Preserving this coastal resource can help to mitigate some of the damage coastal communities see after a hazard event.

Maintaining or restoring oyster reefs can translate into economic benefits as well. For example, in Mobile Alabama, two reef restoration projects, are anticipated to result in increased fish and crab harvests of 6,900 pounds per year which may generate net benefits of $37, 800-$46,200 for producers and consumers per year.   

Submerged Aquatic Vegetation

Submerged Aquatic Vegetation, such as seagrass meadows, are some of the most ecologically and economically valuable ecosystems found in Gulf waters. In the U.S., the gulf region contains more than 50% of the total U.S. distribution of seagrasses.6 Similar to other coastal aquatic habitats, segrasses provide Gulf waters with a wide range of ecosystem services such improved water quality through their ability to 1) uptake nutrients that may contribute to algae overgrowth and 2) trap sediment with their roots and leaves.Additionally, seagrassess provide nursery habitats and predation protection for many recreationally and commercially important species. Unfortunately, 20-100% of seagrasses have been  lost in different regions along the gulf over the past 50 years due to both natural reasons such as high erosion during storm events, and human-induced reasons such as boat groundings. Such losses may result in fragmented seagrass beds which do do not provide the same ecological goods and services as continuous beds. Many Gulf states recognize the importance of maintaining healthy seagrass meadows for the economies of the gulf. “For example, seagrasses were determined to be worth $9,000 to $28,000 per acre for commercial, recreational, and storm protection functions in Texas.”

Beaches

Natural beaches are created by the erosion of upland sediments by rivers, which are then deposited when those rivers reach the sea. If enough sand accumulates, a beach is formed. Beaches grow when: sand from other beaches migrates toward them; sand is artificially deposited by developers; or sea levels lower and expose more land. They may shrink or migrate when waves and currents remove sand and deposit it elsewhere. During large storm events, strong winds and waves can push sand along a coastline and dramatically reshape its profile. Gaining an understanding of sediment processes along the coast, and how they are affected by measures taken to mitigate flooding, is essential to coastal communities. 

Human activities can affect beach size and location. Engineers may build structures such as seawalls and groins in an attempt to manage erosion and flooding. 

  • Seawalls are large barriers, often made of concrete, placed along a shoreline to protect coastal development from flooding. While they are often effective, they can also cause erosion of beaches, inhibit public access to the beach, disrupt continuous habitat for marine life, and be economically difficult as public funds are used to protect private land. 
  • Groins are structures designed to trap sand as it moves down a shoreline. This can cause a buildup of sand on the updrift side of the beach and cause downdrift beaches to become undersupplied with sand.

Beach restoration projects replenish beach sediment lost via longshore drift or erosion to maintain enough width between coastal waters and coastal infrastructure. Many beach restoration projects also seek to maintain or create coastal dune systems stabilized by vegetation. The physical benefits of beach restoration include enhanced protection against the complex coastal processes that result in beach erosion. Stabilized dune systems also serve as a mitigation technique that provide coastal properties with varying degrees of storm protection, by providing a natural barrier that can buffer the destructive forces of flood water caused by sea level rise or storm surge. Local expenditures on beach restoration in the gulf states tend to be high since tourism is a major economic industry in the gulf. For example, an economic evaluation of Florida’s investment in beaches updated in January 2015, revealed that every dollar spent by the state of Florida on beach restoration between Fiscal Year 2010-2011 and 2012-2013, generated $5.40 of additional tax revenue.7

Floodplain

Floodplains, whether coastal or inland, represent portions of land that can slow the advance of storm surge by dissipating wave energy and temporarily sequestering runoff during high precipitation events. This process may aid in mitigating natural hazards and enhancing coastal resiliency.

Floodplain restoration seeks to fully or partially restore a stream’s access to its floodplain. Floodplain restoration techniques may include hydrologic or vegetative. Such restoration techniques seek to restore a floodplain’s natural hydrologic system or native plant community and structure, respectively. Some of the physical benefits of floodplain restoration include enhanced defense against storm surge, nutrient sequestration which aids in enhanced stream water quality, and reduced inundation levels during high tide flooding as sea levels rise.

Forestry

Coastal forests around the Gulf of Mexico include several different types of habitats, and are essential for bird migration. Coastal forests may be defined as wooded communities within 100 km of the coast that usually occur on barrier islands, ridges, delta splays, and along river and bayou drainages. Each year millions of birds stop in the Gulf of Mexico as they migrate north to south and back again. This stop provides a crucial opportunity to rest and replenish energy on the long journey. However, coastal forests are threatened by development, agriculture, logging, cattle grazing, and the introduction of exotic species, among other factors.

The Gulf Stream

An important feature of the Gulf of Mexico is the Gulf Stream, which is a warm Atlantic current that begins in the region and flows north into the Atlantic Ocean. Because of the Gulf Stream, sea surface temperatures in the Gulf of Mexico are normally also warm, which feeds Atlantic hurricanes giving them strength and increasing their likelihood of occurrence along the Gulf Coast. With water and air temperatures increasing worldwide over the past several decades, the frequency and severity of thunderstorms, hurricanes and tropical storms have risen in correlation. In 2017, water temperatures in the Gulf never fell below 73 degrees for the first time on record. The complex interactions between these natural processes, the landscape, human development  and weather can result in flooding and water quality issues.8For more information about coastal processes that exacerbate flood vulnerability, review the Coastal Hazards section of this website.

 

Endnotes

  1. “The Gulf of Mexico at a Glance: A Second Glance,” NOAA National Ocean Service, https://sero.nmfs.noaa.gov/outreach_education/gulf_b_wet/applying_for_a_gulf_b_wet_grant/documents/pdfs/noaas_gulf_of_mexico_at_a_glance_report.pdf

  2. “Wetlands: An Introduction to Wetlands,” ThoughtCo., https://www.thoughtco.com/what-are-wetlands-1435369.

  3. “Multi-Species Recovery Plan for South Florida: Mangroves,” U.S. Fish and Wildlife Service, https://www.fws.gov/verobeach/msrppdfs/mangroves.pdf.

  4. “Mangrove Importance,” World Wildlife Foundation, http://wwf.panda.org/our_work/oceans/coasts/mangroves/mangrove_importance/.

  5. “Habitat Conservation: Oyster Reef Habitat,” NOAA Fisheries, https://www.fisheries.noaa.gov/national/habitat-conservation/oyster-reef-habitat.

  6. "Seagrass Status and Trends in the Northern Gulf of Mexico: 1940–2002," USGS, https://pubs.usgs.gov/sir/2006/5287/.

  7. “Economic Evaluation of Florida’s Investment in Beaches,” Florida Office of Economic and Demographic Research, http://edr.state.fl.us/Content/returnoninvestment/BeachReport.pdf.

  8.  “Gulf of Mexico waters are freakishly warm, which could mean explosive springtime storms,” Washington Post, https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/03/22/gulf-of-mexico-waters-are-freakishly-warm-which-could-mean-explosive-springtime-storms/?utm_term=.568be92a59d7.

  9.  “Oil spill damage spreads through Gulf economies,” CNN Money, https://money.cnn.com/2010/05/30/news/economy/gulf_economy/index.htm.

  10. “Know more about the commercial fishermen in the Gulf of Mexico states,” Mississippi-Alabama Sea Grant Consortium, http://masgc.org/news/article/know-more-about-the-commercial-fishermen-in-the-gulf-of-mexico-states.

  11. “Hurricanes and Marine Life,” Smithsonian Ocean, https://ocean.si.edu/planet-ocean/waves-storms-tsunamis/hurricanes-and-marine-life.

  12. “What’s at Stake: The Economic Value of the Gulf of Mexico’s Ocean Resources,” National Marine Fisheries Service, https://www.nrdc.org/sites/default/files/wat_10051101a.pdf.

  13. “Gulf Intracoastal Waterway,” Texas Department of Transportation, https://www.txdot.gov/inside-txdot/division/transportation-planning/waterway.html.

  14. "ENOW Explorer," NOAA Office of Coastal Management, https://coast.noaa.gov/digitalcoast/tools/enow.html.

  15. “What Will Happen to the Gulf Coast If the Oil Industry Retreats?” CityLab, https://www.citylab.com/environment/2017/09/what-will-happen-to-the-gulf-coast-if-the-oil-industry-retreats/540372/.

  16. “The Economic Impact of the Gulf of Mexico Offshore Oil and Natural Gas Industry and the Role of the Independents,” IHS Global Insight, http://www.noia.org/wp-content/uploads/2015/12/The-Economic-Impact-of-the-Gulf-of-Mexico-Offshoer-Oil-Role-of-Independents.pdf.

  17. “Value of Wetlands,” World Wildlife Foundation, http://wwf.panda.org/our_work/water/intro/value/.

  18. “The 100-Year Flood—It's All About Chance,” USGS, https://water.usgs.gov/edu/100yearflood-basic.html.

  19. “Saffir-Simpson Hurricane Wind Scale,” NOAA National Hurricane Center, https://www.nhc.noaa.gov/aboutsshws.php.

  20. “Building Science Branch Brochure: Wind Hazards,” FEMA, https://www.fema.gov/media-library-data/1496953980230-d52857ef8919276187b3c57d7c851239/Wind_508.pdf.

  21. “What is high tide flooding?” NOAA National Ocean Service, https://oceanservice.noaa.gov/facts/nuisance-flooding.html.

  22. “Climate Change Adaptation Resource Center,” U.S. EPA, https://www.epa.gov/arc-x/climate-adaptation-and-saltwater-intrusion.

  23. “What is Mitigation?” FEMA, https://www.fema.gov/what-mitigation.

  24. “No Adverse Impact: A Toolkit For Common Sense Floodplain Management,” Association of State Floodplain Managers, https://www.floods.org/NoAdverseImpact/NAI_Toolkit_2003.pdf.

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