D.2. Mitigation Projects

Eligible mitigation project types are described below. More information regarding these project types can be found in Part 12.

Property acquisition is the purchase of an existing at-risk structure and, typically, the underlying land from a voluntary owner, as well as the conversion of the land to open space. The existing structure is either demolished or physically relocated to an area outside of a hazard-prone area (e.g., outside of the Special Flood Hazard Area [SFHA], high fire zone area or a regulatory erosion zone). In some cases, undeveloped, at-risk land adjacent to an eligible property with existing structures may be eligible. The property must be deed restricted in perpetuity to open space uses to restore and/or conserve the natural floodplain functions. ^[99]

Structure elevation is the physical raising and/or retrofitting of an existing structure. Elevation may be achieved through a variety of methods, including elevating on continuous foundation walls; elevating on open foundations, such as piles, piers, posts or columns; elevating on fill; and second‑story conversion.

Mitigation reconstruction is the construction of an improved, elevated structure that conforms to the latest building codes on the same site where an existing structure and/or foundation has been partially or completely demolished or destroyed.

Flood risk reduction projects are designed to lessen the frequency of flooding or depth of flood water. Flood risk reduction project types fall into two categories: localized and non-localized.

Localized flood risk reduction projects are used to lessen the frequency or severity of flooding and decrease predicted flood damage within an isolated and confined drainage or catchment area that is not hydraulically linked or connected to a larger basin. Examples of these projects include the following:

• Installation or modification of culverts and other stormwater management facilities.
• Flood diversion and storage measures.
• Slope stabilization or grading.
• Flood protection measures for sewer or other utility systems.
• Vegetation management for shoreline stabilization.
• Flood protection and stabilization for roads and bridges.

Non-localized flood risk reduction projects should lessen the frequency or severity of flooding and decrease predicted flood damage within an area that is hydraulically linked or connected to a drainage basin that is regional in scale. These projects reduce flood hazards in areas larger than that of localized flood reduction projects. The projects may include the construction, demolition or rehabilitation of dams; the construction or modification of dikes, levees, floodwalls, seawalls, groins, jetties, breakwaters and stabilized sand dunes; and the large-scale channelization of a waterway.

Stabilization projects reduce risk to structures or infrastructure from erosion and landslides by installing geosynthetics, stabilizing sod, installing vegetative buffer strips, preserving mature vegetation, decreasing slope angles, and stabilizing with riprap and other means of slope anchoring.

Dry floodproofing techniques are applied to keep structures dry by sealing the structure to keep floodwaters out. Dry floodproofing of historic residential structures is permissible only when other techniques that would mitigate the Base Flood Elevation would cause the structure to lose its status as a historic structure. Dry floodproofing projects are eligible for non-residential and historic residential structures under all HMA programs. Wet floodproofing consists of the use of flood-damage-resistant materials and construction techniques to minimize flood damage to areas below the flood protection level of a non-residential structure, which is intentionally allowed to flood. Wet floodproofing projects are eligible for non-residential structures under all HMA programs.

Tsunami vertical evacuation projects are designed to provide immediate life-safety protection in the event of a tsunami, with sufficient height to elevate evacuees above the tsunami inundation depth. This type of project includes retrofitting existing structures, constructing new vertical evacuation structures, or converting natural topographic features to enable vertical evacuation.

Safe room projects are designed and constructed to provide immediate life-safety protection for people in public and private structures from severe wind events, including hurricanes and tornadoes. For HMA programs, the term “safe room” only applies to structures that meet the criteria in FEMA P-361, Safe Rooms for Tornadoes and Hurricanes, Fourth Edition (April 2021), to provide protection from tornadoes and/or hurricanes, including residential and community safe rooms. This type of project includes retrofits of existing facilities or new safe room projects and applies to both sole-use and multiuse facilities.

Wildfire mitigation projects mitigate at-risk structures and associated loss of life from the threat of future wildfire through:

• Defensible space: Creation of perimeters around homes, structures and critical facilities through the removal or reduction of flammable vegetation.
• Ignition-resistant building materials: Application of ignition-resistant techniques and/or non-combustible materials on new and existing homes, structures and critical facilities.
• Fire suppression systems: Exterior sprinkler systems to help extinguish flames and prevent the spread of fire to nearby buildings or combustible vegetation.
• Fuels reduction/vegetation management: Removal of vegetative fuels proximate to at-risk structures that, if ignited, pose a significant threat to human life and property, especially critical facilities.
• Post-wildfire flooding prevention and sediment reduction measures: Preventative measures that protect property at the base of slopes made vulnerable to erosion and/or flooding because of loss of vegetation or changes in soil composition post-wildfire.

Retrofits are modifications to existing structures to reduce or eliminate the risk of future damage and to protect inhabitants. Retrofits can be structural or non-structural and can be done for a range of hazards.

Structural retrofits address the structural elements of a building or facility that are essential to prevent damage, including foundations, load-bearing walls, lateral load-resisting systems, beams, columns, building envelope, structural floors and roofs, and the connections between these elements. An example of an earthquake structural retrofit would be the installation of base isolation or energy dissipation systems in accordance with the latest building codes and standards.

Non-structural retrofits modify the non-structural elements of a building or facility to reduce or eliminate the risk of future damage and to protect inhabitants. Non-structural retrofits may include anchoring major mechanical, electrical, plumbing and architectural components to load-bearing structure or foundation and bracing of building contents to prevent earthquake damage or the elevation of utilities.

Structural and non-structural retrofits reduce or eliminate risk of future damage to existing infrastructure. Retrofits may include existing roads and bridges or infrastructure/lifelines such as energy utilities, communications systems and public water systems.

Secondary power sources increase power system resilience and mitigate the impacts of natural hazards while increasing the resilience of critical functions.

The purchase and installation of secondary power sources and related equipment, such as generators, microgrids, solar photovoltaic systems, and battery back-up systems are generally eligible if they are cost-effective, contribute to a long-term solution to the problem they are intended to address, and meet all other program eligibility criteria. Additional secondary power sources not listed in the HMA Guide may be eligible and will be reviewed on a case-by-case basis.

Warning systems projects include equipment and systems to warn people about natural hazards such as earthquakes, tornadoes, wildfire, tsunamis and flash floods.

Aquifer recharge, storage and recovery projects serve primarily as a drought management tool, but they can also be used to reduce flood risk, mitigate saltwater intrusion and restore aquifers that have been subject to overdraft.