The purpose of this section is to provide explanation of the coastal conceptual risk framework and how it pertains to the CHART SCT. Coastal risk is conceptualized as a function of hazard, coastal system response, exposure, and vulnerability and is based on the risk framework shown in ER 1105-2-101.

Risk = f(Hazard, System Response, Exposure, Vulnerability)

In the context of the SCT effort, the conceptual coastal risk framework provides an outline for developing the risk statements a project delivery team (PDT) is trying to address with a planning feasibility study. Topics covered in this section cover explanations of the following:

Explanation of each risk factor in the conceptual coastal risk framework,
Relevant considerations of each risk factor,
The role of each risk factor in developing risk statements

For the SCT, the purpose of risk statements is to provide a comprehensive, simple language method for describing the risk for a given stretch of coastline within a given planning reach pursuant to the development of scoping level risk estimates, determining the level of effort. Risk statements will provide a point of reference for SCT planning objectives. Risk statements when properly developed should link a scoping level risk assessment to an estimate of the level of effort needed to study that risk in a feasibility study.

Hazard(s)

For the purposes of coastal storm risk management (CSRM), hazards are typically considered as

Coastal storm events associated with a probability distribution that lead to adverse exposure impacts due to inundation, wave attack, and erosion,
Coastal processes that may not be associated with a probability distribution but could worsen conditions over time to areas of concern.

However, WRDA 2022 Section 8106 Implementation Guidance requires that coastal studies consider more than the traditional coastal storm risk considerations. Table X provides a list of all the potential hazard sources that may be relevant to a CSRM effort. In some cases, two or more of these hazard sources could be prevalent within the study area, complicating the risk assessment. It is the responsibility of the PDT to consider the study authority along with all relevant hazard sources and make judgements regarding what drives, complicates, or compounds the risk. The outcome of that judgement will determine the complexity of the risk assessment and have implications for the study scope.

Hazard Source	Hazard Description
Coastal Storm Event	Tropical or extratropical storm events that cause harm via erosion, inundation, an/or wave attack.
Fluvial Flood Event	Riverine discharge of any magnitude or frequency along tidally influenced rivers that cause harm by flooding
Precipitation Event	Rainfall event of any magnitude or frequency that causes harm due to flooding
Seasonal Lake Levels	Seasonal variation in lake levels that lead to harm due to inundation and/or erosion in Great Lakes coastal settings
Astronomic Tides	Periodic rise and fall of water along coastal areas due to gravitational interactions and celestial movements. Tidal forces can cause increased water levels during storm and rainfall events leading to inundation harm.
Coastal Processes	Wave action/ energy, littoral drift along a shoreline that causes shoreline erosion and/ or accretion
Relative Sea Level Change	Combination of subsidence and sea level rise captured and reflected as an amount of sea level rise on an annual basis. RSLC can exacerbate erosion, inundation, and wave attack harm during storm events, or combine with rainfall and or tide to cause nuisance flooding.

With respect to the hazard, the risk statement should identify all relevant hazard sources and indicate whether those sources are risk drivers, risk complicators, or risk compounders. A brief description of each risk driver, and the likely impact on scoping is as follows:

Risk Category	Description	Study Scope Implications
Risk Driver	Hazard source is anticipated to be a primary driver of the risk.	Models and analysis should be focused on estimating risk from this hazard source. Even though this is a significant part of the scoping effort, this is the least complex for the risk analysis if there is only one risk driver.
Risk Complicator	Hazard source could add further complications to the risk assessment.	Level of effort could be minimal if existing models and analysis take this into account. There may be additional effort involved that could impact study scope but nothing significant. (additional parameters or scenario analysis)
Risk Compounder	Hazard source is expected to compound the risk. Hazard impact on the risk cannot be properly represented without accounting for this effect.	Compound effect need be incorporated into modeling and analysis. Model inputs need to be modified in some significant way. Additional effort to represent, explain, and defend this effect is expected to be significant for the study scope.

Coastal System Response

Coastal System Response refers to how the coastal system within the area of concern is likely to respond to the loading condition created by the hazard source(s). This response depends on a variety of factors such as location, waterbody type, landform type, wave energy environment and shoreline configuration (offshore, nearshore, foreshore, and backshore). The considerations for characterization of a coastal system response include the shoreline category, shoreline type, hazard modification features, and shoreline change rates.

Shoreline Categories

This section has discussion on the landform waterbody combinations that constitute the different physical attributes in a coastal setting. Major waterbody types include oceans, bays, interior channels, estuaries, as well as tidally connected inlets, rivers, and lakes. Landform types under consideration include barrier island and mainland features. Shoreline categories can be a significant factor in determining the level of study effort needed to understand the exposure size and characteristics. Coastline categories shown in the table below provide insight into the wave energy climate, hazard type(s)magnitude, and exposure extents

Shoreline Category	Description	Study Scope Implications
Ocean-Barrier Island	Ocean facing barrier island shorelines. Exposure extents tend to be narrow, oriented parallel to the shoreline and subject to the most wave energy and shoreline dynamism. Exposure associated with this shoreline category can also be subject to risk from back-bay flooding.	Relatively fewer assets subject to risk Important to understand asset foundation to determine erosion susceptibility Populations most likely to evacuate
Ocean-Mainland	Ocean facing mainland shorelines. Exposure extents tend to be narrow, oriented parallel to the shoreline and subject to the most wave energy and shoreline dynamism. It may be possible to have other flood sources depending on orientation relative to tidal rivers.
BackBay-Barrier Island	Bayside facing barrier island shorelines. Exposure tends to be lower lying and larger in flood extents relative to exposure centered along the ocean facing coastline.	Assets likely less susceptible to high wave energy Mainland population evacuation rates may be lower / different from ocean facing Potential for larger and more diverse asset inventory and vulnerable critical infrastructure
BackBay-Mainland	Bayside-facing mainland shorelines. The exposure tends to be larger, lower lying, with less wave energy relative to an ocean-facing mainland.
Inlet-Barrier Island	Inlet-facing Barrier Island shorelines. These coasts may be subject to significant coastal dynamism that could result in significant shoreline change.
Inlet-Mainland	Inlet facing mainland shorelines
Riverine-Barrier Island	Barrier island shorelines along tidally connected rivers
Riverine-Mainland	Mainland shorelines along tidally connected rivers
IWW-Barrier Island	Barrier island shorelines facing intracoastal waterways Coastlines tend to be more sheltered with low lying, but larger exposure extents relative to ocean-facing shorelines. Could also be a source of risk to an ocean facing coastline.
IWW-Mainland	Mainland shorelines facing intracoastal waterways. Coastlines tend to be more sheltered with low lying, but larger exposure extents relative to ocean-facing shorelines.
Lake-Mainland	Tidally connected or coastal lake facing mainland. Subject to erosion and inundation from seasonal lake levels and storms.

Shoreline Types

In addition to the coastal setting, the shoreline type provides additional detail needed for the characterization of the coastal system response. Shoreline Types depicted here are more or less based on the ESI shoreline types developed by NOAA( ESI Shoreline Types | response.restoration.noaa.gov ). These shoreline types could be defined with additional dimensions and parameters that would add more insight regarding different profile transect configurations. The profile dimensions for a sandy beach (upland, dune, berm, submerged berm) will be different from profile transect dimensions for a wetland or a tidal flat. Please note these shorelines are classified based on what is likely to have a constant water load. Shoreline type is a large determinant of system response, measure selection, and siting.

Shoreline Type	Description	Study Scope Implications
Rocky Shores / Exposed Solid Man-Made Structures	Exposed to high wave energy or tidal currents with a narrow intertidal zone. Strong wave reflection patterns are common given vertical impermeable substrate. Typical of solid robust existing seawalls on ocean facing coastlines. Areas are likely resilient in the face of high energy coastal forcing	Potential for erosion Potential for failure
Bluffs/Cliffs	Characterized by elevated uplands separated from water bodies by steep slopes. Vulnerable to erosion and/or subsurface geotechnical failures.	Capture of erosion patterns over time.
Beaches	Typically sandy but considerations for cobble and mixed cobble/sand beaches may be needed.	cross shore sediment movement erosion rates sand sources emergency nourishment CBRA zones
Revetment Shoreline	Shoreline armoring measure to prevent erosion and reduce wave energy, run up, and overtopping. Please note this is different from a sandy beach shoreline with a revetment. Does not improve overflow conditions.	Potential for failure Response given failure
Developed Manmade Shoreline	Consist of developed shorelines in relatively more urbanized areas in relatively low wave and tidal energy environments.	Potential for failure Response given failure
Tidal Flats	Tidal flats and overwash fans are intertidal areas where sediment has been deposited by rivers, tides, storm surge, or waves. Tidal flats are located between the spring high and low tide levels, lack rooted vegetation, and span a range of composition from mud to sandy flats which are found in sheltered bays, estuaries and coasts that are protected by barrier islands (Schutte et al. 2019). Large coastal storms and their associated high winds, waves, and tides can result in overwash of the beach and dune system. During storm conditions, elevated storm tides and high waves may erode beaches and dunes, and the eroded sand can be carried landward by surging water. The sand and water may wash over or break through the dunes and spill out onto the landward side of peninsulas and barrier islands. This deposit is usually fan-shaped and therefore is known as an overwash (or washover) fan. Engineered overwash fans are implemented to increase overall barrier island stability and back bay coastal storm risk management capacity by increasing its width/volume and providing a substrate suitable for wetland growth. In addition, strategic unconfined placement of finer sediment within nearshore tidal flats to increase widths and heights and net sediment availability to marshes is growing in practice. Sediment could be mined from borrow sources ‘outside’ the sediment budget system such as offshore borrow sites similar to those used for beach restoration projects. Other sources may include beneficial use of dredged sediments from adjacent back bay and inlet channels.	Natural environments that may have significant environmental resources or may provide protection and wave attenuation to more developed areas further inland. Studies may be needed to understand the species or habitats at stake or how these types of shorelines are likely to evolve over time in FWOP or FWP conditions. Other considerations include Type of measures Mitigation
Wetlands	Wetlands, also referred to as tidal fringe, tidal-flat or estuarine wetlands, and as brackish or saltwater marsh, occur along the intertidal zone of marine, estuarine, or riverine systems. Specifically, these wetlands occur along the fringe of drowned river valleys, barrier islands, lagoons, and other coastal waterways.

Hazard Modification Features

Shoreline categories and types provide detail on the overall system physics, and shape how the hazard propagates through the physical system. However, there may be additional structures that further impact the coastal system response. These structures are man-made coastal risk mitigation features that have a material impact on the risk but cannot be accounted for with a scoping level risk estimate. These features should be noted in the risk statement because accounting for the effect of existing, or future risk mitigation efforts should increase the level of effort needed to obtain an FWOP life cycle coastal risk estimate. Measures that impact the system response can be grouped into coastline armoring, coastline restoration, coastline stabilization, and groundwater storage.

Coastline Armoring

The method behind armoring is to reduce the frequency and/or severity of the interactions between coastal storm hazards and exposure with a man-made physical barrier. These measures are prevalent in situations where the amount of land between hazard and exposure is relatively narrow, and there is enough development to warrant the cost of the risk management measure. Coastline armoring measures consist of floodwalls, seawalls, bulkheads, revetments, road elevation, levees, ring walls, and surge gates.

Coastline Restoration

Restoration manages risk by maintaining a minimum shoreline width between the hazard and the exposure. Its purpose is to provide risk management to upland development. Sediment material can be placed on the sub-aerial beach, as underwater mounds, across the subaqueous profile, or as dunes. Material can also be placed in a manner that restores barrier islands, coastal wetlands, and maritime forests. Coastline restoration measures include beach nourishment, barrier island restoration, wetland restoration.

Coastline Stabilization

Coastline stabilization manages coastal storm risk by moderating the shoreline change rate to sustain a natural shoreline barrier between the hazard and the exposure. This approach moderates the coastal sediment transport process and reduces the local erosion rate. These structures should be considered where chronic erosion is a problem due to the diminished sediment supply. Coastline stabilization measures include groins, breakwaters, and living shoreline type measures. They are often combined with beach nourishment to reduce downdrift impacts or the number of nourishment events needed to maintain a beach restoration.

Groundwater Storage

Measures that manage the amount of water that can seep into the ground per unit area and time. These include alternatives such as pumps, storage and or other conveyance type features.

System Response Mechanisms

System Response Mechanisms are the final consideration of the system response component of coastal risk. This includes stage volume functions, fragility curves, erosion rates, planform rates, as well as longshore and cross shore change rates. A more in depth description of these mechanisms and their impact on scoping is included in Table X

System Response Mechanism	Description	Study Scope Implications
Stage volume functions / topography
Overtopping
Fragility curves & failure thresholds
Erosion rates
Recovery Rates
Longshore sediment transport rates
Cross-shore morphology change

Exposure

Exposure describes who and/or what may be harmed by the hazard source. It incorporates the subject of desired risk management, such as asset/structure inventories, critical infrastructure, population at risk, and habitat acreage. Since this risk factor deals with the subject of risk management it defines the units that alternative impacts should be measured in. Human life, and public & private property are the most significant exposure types and form the primary basis for decision making. However, other exposure types that are relevant for plan formulation include environmental justice / economically disadvantaged communities, critical infrastructure, local economic disruptions, cultural resources, and environmental resources. See the table below for more detail.

Exposure Category	Description	Principles and Guidelines Account(s)	Study Scope Implications
Human Life	Lives lost due to due to direct flooding. According to guidance document, there is a compelling interest in reducing risk to human life.	OSE- Life loss due to the effects of direct flooding or structure collapse.	If hazard source conditions are severe enough to cause life loss, the study should quantify that effect. Study effort should be devoted to determining the population at risk (PAR) and population evacuation rates. Larger exposure extents are likely to translate to greater study effort in the life safety risk analysis.
Public & Private Property	Physical damages to property reflected in dollars. 1st order damages,	NED - Negative change in the national value of goods and services due to property loss.	Study effort must be expended to understand the asset inventory. As asset quantity, complexity, and variability increase, so will the study scope.
Critical Infrastructure	Defines infrastructure that is critical for community function. Infrastructure can be considered community lifelines as they support public health & safety, transportation, energy, water supply, and/or wastewater treatment functions.	NED - NED effects include physical damages to infrastructure, however there may be additional NED effects due to service loss. OSE - OSE effects include increased potential for risk to public health and safety.	Involves developing an inventory of critical infrastructure items. Depending on the inventory item and its importance, additional effort may be needed to develop exposure costs and damage relationships.
Land Loss & Condemnation	This defines the potential for permanent loss of land, property, or infrastructure within the exposure. This could be caused by either loss of upland (nearshore land) and/or permanent inundation due to rising sea levels and tide.	NED - Land loss is an NED damage reflected as a loss of developable land from erosion or sea level rise. Condemnation would refer to the permanent loss of property due to erosion or an inundation frequency that renders the property unusable. Condemnation could be an NED, OSE, or RED effect depending on the situation. PDTs should consult with policy subject matter experts for more information.	Studies may need to be done to determine the amount of land lost and its nearshore land value. Study effort will need to be devoted to understanding the conditions under which condemnations will occur and translating that to a performance/ decision making metric.
Business Losses	Loss of property (business, or residential) could reduce regional economic output by preventing people from working, destruction of capital equipment, and/or inventory. This would reduce the value of local economic output.	NED - NED effects of local business losses is likely to be complicated and labor intensive as additional analysis must be completed to net out all transfer effects. RED - Losses in regional economic output and/or wages could be reflected as an RED loss. OSE -RED losses could be reinterpreted as losses in economic vitality which is an OSE metric.	Depending on the importance of this metric to making plan formulation decisions, studies may need to be done to understand any losses in economic output given the NED losses. Tools such as ECAMS, RECONS, IMPLAN, etc. may need to be used. If this output is anticipated to be connected to NED, scopes would need to be increased to net out the transfer effects, and/or capture any other relevant changes to the national value of goods and services.
Recreation	Loss of availability or value of a recreation resource due to hazard sources or risk mitigation efforts.	NED- Recreation is incidental for project purposes, but it is relevant for economic justification.	If recreation is important, additional effort would need to be added to study scope.
Cultural Resources	Losses to buildings and/or sites of cultural significance from hazard sources	EQ/ OSE - Cultural resource losses could be considered EQ or OSE effect.	Study effort includes research and inventory development and understanding the risk and harm to these resources. Monetized effects of cultural resource loss will require additional study cost.
Environmental Resources	Potential loss of species and/or habitat buildings and/or sites of cultural significance from hazard sources.	EQ - Losses of species or habitat could be considered an effect to the Environmental Quality P&G account.	Study effort includes research and inventory development and understanding the risk and harm to these resources. May require modeling of environmental resource loss to determine mitigation costs.
Environmental Justice / Economically Disadvantaged Communities	Populations that are more likely to be more vulnerable to the impacts of public and private property loss, or more susceptible to life loss due to socio-economic, factors. The extent of life loss, property loss, critical infrastructure damage, land loss, condemnation, business loss as well as environmental and cultural losses within an EJ community should be evaluated.	Any of the aforementioned NED, RED, OSE, and EQ effects can be evaluated within designated E.J. communities.	EJ community analysis will involve data collection and compilation available data sources as well as coordination with the non-federal sponsor

Vulnerability

Vulnerability is the relationship between the hazard and the extent of the harm from the exposure. Depth damage functions and depth mortality functions are examples of vulnerability from a conceptual standpoint. Retrofit measures such as floodproofing and elevating assets reduce vulnerability by adjusting or shifting the hazard to harm relationship such that each increment of hazard results in less harm to the exposed asset or population.

Vulnerability Component	Description	Study Scope Implications
Inundation (Submergence)
Inundation (Stability)
Wave Attack
Erosion
Lethality Relationships

Measures, Alternatives & the Coastal Risk Framework

Hazard Modification Method	Measures	Description	Study Scope Implications (FWOP/FWP)
Coastline Armoring	Floodwall	Coastal floodwalls are structures built to manage the risk of damage associated with surge tide and waves in relatively small areas with limited space for flood risk management. Typical types of flood walls include cantilever T-type, I-type, and braced sheet-pile structures. These structures are generally located landward of the normal high-water line so that they are inundated only by hurricane or other surge tide events. Unlike wider, more stable levees, narrow floodwalls require significant reinforcement and anchoring construction to prevent collapse from hydrostatic pressure.	Coastline Armoring Performance (FWOP/FWP) - How will coastal armor modify the hazard conditions? Upland erosion Coastal storm inundation Waves FWOP Assumptions - How does existing coastal armor modify the hazard condition? Will coastal armor be built in the future? If so, how will it modify the hazard conditions? Potential Failure Is the failure of coastal armor significant for risk assessment, plan formulation and/or plan selection? Response given failure Failure Types Failure thresholds Fragility Curve Does fragility change over time in a life cycle? Potential Effects Real estate Environmental effects Design maturity
	Seawall	A seawall is a structure built parallel along a segment of coast with a principal function to reduce overtopping and consequent flooding of land and infrastructure behind it due to storm surges and large waves (typically greater than 5 feet).
	Bulkhead	Bulkheads are vertical shoreline stabilization structures that primarily retain or prevent sliding of the land. A secondary purpose is to protect the upland against erosion due to low to moderate waves. Types of bulkheads consist primarily of anchored and cantilevered walls commonly built of vinyl, concrete, steel, aluminum, or timber piles.
	Revetment	A revetment typically refers to a layer or layers of stone that protect an embankment, or shore structure, against erosion by wave action or currents. Revetments are built at a slope and typically constructed with an assorted mass of quarry stone, concrete rubble or a well-ordered array of structural elements that interlock to form a geometric pattern.
	Road Elevation	Road elevation involves raising roads in place so that the road sees a reduction in frequency and/or depth of flooding during high water events. Selection of proper elevation method depends on flood characteristics, such as flood depth or velocity.
	Levees	Levees and dikes are embankments constructed along a waterfront to prevent flooding in relatively large areas. They are typically constructed by compacting soil into a large berm that is wide at the base and tapers toward the top. Grass or some other type of non-woody vegetation is usually planted on the levee/dike to add stability to the structure. If a levee or dike is located in an erosive shoreline environment, revetments may be needed on the waterfront side to reduce impacts from erosion, or in cases of extreme conditions, the dike face may be constructed entirely of rock. Levees may be constructed in urban areas or coastal areas; however, large tracts of real estate are usually required owing to the levee width and required setbacks. Depending on the density of development of a vulnerable area, levees and floodwalls are often constructed as a system whereby floodwalls are interspersed between levee segments as available property space dictates.
	Ringwalls	Ringwalls, small floodwalls, berms, or ring levees are located away from the structure to be protected and prevent the encroachment of floodwaters. They may surround the structure or protect only the low side of the property. A ringwall is considered nonstructural because it is intended to be used to protect a single structure from flooding, and not intended to influence the occurrence or magnitude of flooding in the floodplain, which is what structural measures do. These relatively small structures are distinguished from large public investments by their scale and location on privately owned land. Unlike some other floodproofing measures, a well-designed and constructed freestanding floodwall or berm results in no floodwater forces on the structure itself. Consequently, if the floodwall or berm is not overtopped or otherwise failed, the structure is not exposed to damaging hydrostatic or hydrodynamic forces.
	Surge Gate	Storm surge barriers are barrier ‘systems’ that manage risk to an estuary or bay and consist of a series of coastal dikes, gates, and in some cases, navigation locks. In most cases, the barrier consists of a series of movable gates that stay open under normal conditions to maintain flow and are closed when storm surges are expected. The gates are sliding or rotating steel structures supported in most cases by concrete structures on pile foundations (USACE 2002). In addition, storm surge barriers are usually combined with other flood risk management measures such as levees and floodwalls.	Size of the exposure area impacted by the surge gate Operational conditions Potential environmental impacts Potential failure Design maturity
Coastline Restoration	Beach Nourishment	Beach nourishment, also commonly referred to as beach restoration or beachfill, typically includes the placement of large quantities of sand to either replace eroded beaches or increase the size (width and/or height) of an existing beach and dune system. Material similar to the natural sand is mechanically placed (i.e., hydraulic cutterhead, hopper and/or truck haul with land-based construction equipment) on the eroded part of the beach. Beach and dune nourishment can manage risk not only to the beach where it is placed and infrastructure landward of the beach, but also downdrift stretches by providing an updrift point source of sand (USACE 2002). Most coastal engineering practitioners consider beach nourishment as a technically sound coastal storm risk management engineering alterative when properly designed and placed in the appropriate location (National Research Council 1995). A comprehensive database of beach projects in the United States can be found at http://beachnourishment.wcu.edu. Beach nourishment can also be considered a nature-based feature.	Beach Nourishment Performance Longshore sediment transport /Erosion Coastal storm Inundation Wave heights and energy Nourishment (FWOP/FWP) Beach configuration Volume Dune height & width Berm height & width Cost - Sand sources, trucking vs dredge, nourishment interval
	Barrier Island Restoration	Barrier islands are detached offshore islands that are located between two inlets. Restoration of these landscape features typically includes the placement of large quantities of beach quality sandy material to either replace eroded island shorelines, replace breach areas, or increase the size (width and/or height) of an existing island. Typical restoration includes the entire barrier island such as the beach, dune system, and back bay platforms, but can also include incorporation of smaller dunes, herbaceous woody areas, beaches, tidal flats, and wetlands.	Barrier Island System Performance Coastal storm Inundation Wave heights and energy Barrier Island Evolution Environmental Resources (Species/Habitat)
	Wetland Restoration	Wetlands, also referred to as tidal fringe, tidal-flat or estuarine wetlands, and as brackish or saltwater marsh, occur along the intertidal zone of marine, estuarine, or riverine systems. Specifically, these wetlands occur along the fringe of drowned river valleys, barrier islands, lagoons, and other coastal waterways. The wetlands receive their water primarily from marine or estuarine sources and are affected by astronomical tidal action (Shafer et al. 2002). Although this definition includes a broad group of wetlands commonly known as intertidal marshes, salt marshes, forested riverine swamps, and mangrove swamps and correspond to the emergent, scrub-shrub, and forested wetland class designations used by (Cowardin 1979), in the MCL it is more narrowly defined as intertidal and salt marsh.	Wetland System Performance Coastal storm Inundation Wave Attenuation Wetland Evolution Environmental Resources (Species/Habitat)
Coastline Stabilization	Groins	Structures that extend perpendicular to the shoreline to intercept sand moving parallel to the beach to retain sand, reduce beach erosion, and break waves. This measure is often implemented as a single groin known as a terminal groin or as a groin system (series of groins) extending across a section of ocean‐facing shoreline. Groins are usually constructed with stone along ocean‐facing shorelines but can also be constructed out of timber and metal sheet piles in more sheltered areas such as bays.	Coastline Stabilization Performance Shoreline change moderation Wave Attenuation Longshore sediment transport /Erosion Environmental Resources (Species/Habitat)
	Breakwaters	Breakwaters are relatively short, nearshore structures built parallel to the shore just seaward of the shoreline in shallow water depths, with the principal function of reducing beach erosion through reducing wave height and thus, longshore and cross-shore sediment transport. Like groins, a series of detached breakwaters can be used to control the distribution of beach material along a coastline. When used as harbor risk management, breakwater structures are typically attached to the shore and enclose the harbor basin to reduce the impacts from waves. Breakwaters are usually built as rubble-mound quarry stone structures but can be constructed from a variety of materials such as geotextile and concrete.
	Reef Breakwaters	Coral reefs are underwater ecosystems characterized by reef-building corals. They are found in areas with relatively high water temperatures, good water clarity, low phosphates and nitrogen nutrients, and moderate wave energy (FDEP 2020b). The most common coral reefs found in Florida, Puerto Rico, and the U.S. Virgin Islands are fringing, shelf, bank, patch, and deepwater reefs. Structural restoration of coral reefs has included boulders, sinking of wrecks, or relocation of rocks/dead coral heads. Additional engineering options, such as the bioengineered breakwater units discussed below under living shoreline reefs, are still an emerging technology for use in coral reef restoration projects along with recent advances in custom-designed three-dimensional printed reefs. Biological restoration includes transplanting living coral colonies either onto existing damaged reefs and/or the incorporation of structures into restoration.
	Living Shorelines	A living shoreline sill is a coast-parallel, low-profile structure built with the objective of reducing the wave action on the shoreline. These structures are designed to dissipate wave energy and reduce bank erosion, causing waves to break on the offshore structure, rather than on the natural, more fragile shore (Miller et al. 2015). Sills can be designed using a number of different materials, including rock, armor stone, grout-filled bags, geotubes, rock gabion baskets and natural materials such as oysters.	Coastline Stabilization Performance Shoreline change moderation Wave Attenuation Longshore sediment transport /Erosion Environmental Resources (Species/Habitat)
Groundwater Storage	Pumps
Groundwater Storage	Storage
Temporary & Permanent Retreat	Buyout & Acquisition	Buyout/acquisition involves the purchase and elimination of flood damageable structures, allowing for inhabitants to relocate away from flood hazards. This measure is the most dependable method of protection and provides the benefit of use of the evacuated floodplain.
	Relocation	Relocation involves moving the structure to another location away from flood hazards. Relocation is a very dependable method of protection and provides the benefit of use of the evacuated floodplain.
	Flood Warning Systems / Emergency Preparation / Evacuation Plans	Flood warning systems alert inhabitants in flood-prone areas of impending high water. Depending on the type of warning system and advance time, inhabitants could evacuate damageable property and themselves from the flood-prone area. These measures provide immediate risk management to security of life, health, and safety (OSE) by alerting the population at risk to begin protective action initiation. The nature of the risk management is immediate, temporary, and works by influencing the decision-making of individuals. It strengthens community resiliency by increasing preparedness. Emergency Preparation - Local officials are encouraged to develop and maintain a flood emergency preparedness plan (FEPP) that identifies hazards, risks and vulnerabilities, and encourages the development of local mitigation. The FEPP should include the community’s response to flooding, location of evacuation centers, evacuation routes, and flood recovery processes (USACE 2019b). Evacuation Plans require detailed hydrologic analyses for determining the rate of rise of floodwaters for various rainfall or snowmelt events. When used in conjunction with flood warning systems, this measure can provide significant loss of life avoidance and flood damage reduction benefits.
Asset/ Building Retrofit	Building Elevation	Structure elevation involves raising the assets in place so that the structure sees a reduction in frequency and/or depth of flooding during high water events. Elevation can be done on fill, foundation walls, piers, piles, posts, or columns. Selection of proper elevation method depends on flood characteristics, such as flood depth or velocity.
	Dry Floodproofing	Dry floodproofing involves sealing building walls with waterproofing compounds, impermeable sheeting, or other materials to prevent the entry of floodwaters into damageable structures. Dry floodproofing is applicable in areas of shallow, low velocity flooding.
	Wet Floodproofing	Wet floodproofing measures allows floodwater to enter the structure. Vulnerable items, such as utilities, appliances, and furnaces are waterproofed or elevated to higher locations. Allowing floodwater to enttural damage.