The challenges with flooding in Region Seven and across Louisiana are widespread, with many contributing factors. These contributing factors include weather-related events — precipitation events, coastal storms, and tidal flooding — and are increasing in frequency, intensity, and duration. However, the effects of legal and policy decisions, including those relating to development and land-use patterns, drainage infrastructure, pervious and impervious surface area, and more, have also created challenges affecting where and how people can live and their overall resilience. Land use and development affect how readily water is (or is not) able to move through natural channels, and whether the natural environment has the capacity to accommodate changing flood patterns. Natural filtration capacity is lost as open space is converted to other uses. Development typically increases impervious surface areas, which leads to a greater velocity of stormwater runoff during precipitation events or other high water conditions, thus exacerbating flood risk. Sometimes, development also involves the use of earthen fill to elevate areas in the floodplain that are to be developed further. This is intended to reduce flood risk to the development itself by elevating the property. However, in some cases, this can actually exacerbate flood risk for surrounding (lower elevated) properties, and even the raised property itself, depending on the characteristics of the fill. That is, earthen fill can affect the overall ability of the land to store and convey water, increasing flood risks for upstream and downstream communities.See footnote 1
Given the significant impact of development on flood risk, it is important for local governments to have plans and regulations in place that seek to avoid or mitigate flood-related impacts from development as much as possible. Based on research and outreach conducted to inform the Regional Vision, drainage issues have been cited as a primary challenge by many of the parishes in Region Seven. It is also important for development and infrastructure itself to be designed with flood resilience in mind, particularly as some parts of Region Seven are experiencing historic growth, with recent escalations in the rate of permit applications filed.
This objective focuses on the need to evaluate and mitigate flood risk in areas that may be subject to new development. In addition, it encourages policymakers to consider whether existing standards are sufficient to protect new homes, as well as neighboring areas upstream and downstream.
Policymakers should contemplate policy options that impose stricter flood mitigation standards for new development, holistically and in the context of other factors, like housing needs and affordability, both of which can be affected by development regulations. Furthermore, the recommendations in this objective should also be considered in the context of flooding risks associated with existing homes and infrastructure, and the legal, planning, and policy mechanisms that can be implemented to help address these risks. The recommendations contained in this objective do not address this risk to existing structures, except to the extent that regulations discussed may also apply to substantial redevelopment.
Informed by the latest data on local flood risk, local governments can seek to avoid or mitigate flooding from new development through one or a combination of three types of actions:
As discussed in the Background for Goal Two, the National Flood Insurance Program (NFIP) establishes minimum standards for floodplain management and regulation within the Special Flood Hazard Area (SFHA, also referred to as the floodplain). Among these requirements is a minimum standard that building sites, subdivision proposals, and other proposed new developments in the floodplain are determined to be “reasonably safe from flooding.”See footnote 2 Supported by the latest available data and modeling, this standard can help local governments justify decisions to go beyond minimum NFIP requirements with respect to development proposed within a designated floodplain. Local governments may wish to consider these legal and policy options outlined above among the range of tools and approaches to reduce the risk of flooding to properties.
Much of the discussion below relates to technical classifications of how the Federal Emergency Management Agency (FEMA) defines geographic zones or areas of the floodplain under the NFIP based on factors like frequency and intensity of flood risk and proximity to the coast. These zones also have impacts on local land-use and zoning. This objective does not define each of these zones in text. For more information about each of these zones, see the Congressional Research Service’s Introduction to the National Flood Insurance Program. Additional definitions and information relating to the NFIP can be found in the Goal Two Background.
The minimum NFIP floodplain management standards require that “all new construction and substantial improvement of residential structures” in the regulatory floodplain (also known as the Special Flood Hazard Area or SFHA) be elevated at or above the base flood elevation (BFE).See footnote 3 However, given the growing frequency and intensity of flood events, including outside the SFHA,See footnote 4 some local governments have adopted or are considering incorporating new or enhanced freeboard requirements in parish and municipal ordinances.
Credit: Calcasieu Parish, Louisiana.
Freeboard refers to “an additional amount of height above the [BFE] used as a factor of safety in determining the level at which a structure’s lowest floor must be elevated or floodproofed to be in accordance with state or community floodplain management regulations.”See footnote 5 Freeboard can help account for unknown or unanticipated factors that can contribute to flood heights greater than the BFE, such as impacts from development in the watershed, wave action, blockage of infrastructure (e.g., bridges and culverts) by debris, or sea-level rise. Additionally, if a community that participates in the Community Rating System (CRS) program would like to work towards achieving a rating of eight or higher, they must have at least one foot of freeboard adopted.See footnote 6 Thus, freeboard not only reduces the risk of a structure flooding, it is also an explicit way to ensure that a parish or municipality can reap the full benefit of CRS points that are earned from activities to reduce flood insurance premiums across the participating community.
There are different ways that local governments can approach freeboard requirements, which are typically implemented in local ordinances including the floodplain ordinance. The following portion of this objective will contain potential provisions to be implemented or amended within an ordinance. While this list is not exhaustive, potential recommendations include:
Description: An illustration of the difference between development standards applied in flood zones. Credit: Federal Emergency Management Agency. |
Communities adopting freeboard requirements can receive points under CRS Activity 430, Higher Regulatory Standards — Freeboard (432.b), with the total amount of points depending on the extent of freeboard requirements (relative to the SFHA), the height of freeboard required, and whether or not fill is also regulated.See footnote 15
For properties in the SFHA that are not in the designated regulatory floodway,See footnote 16 the placement of earthen fill is a common practice in the development community to help raise structures above the BFE.See footnote 17 Upon elevating with fill, property owners can petition FEMA to request that the area be removed from the SFHA, in which case requirements to comply with minimum NFIP floodplain management standards would no longer apply.See footnote 18 The same “reasonably safe from flooding” standard also applies when earthen fill is used to elevate an area proposed for development to or above the BFE. That is, when a map revision is sought to remove a filled area from the SFHA, the community must provide written assurance that “the land and any existing or proposed structures to be removed from the SFHA are ‘reasonably safe from flooding.’”See footnote 19
While the use of fill can help reduce flood risk for the structures built on top of the filled area, it can exacerbate flooding challenges for neighboring properties and communities as it “reduces floodplain storage capacity, can deflect waves onto neighboring property,” as well as having adverse impacts on environmental quality (e.g., wetlands, vegetation, and water) and functions such as drainage.See footnote 20 One option for local governments is to include additional restrictions or limitations on the use of fill in the SFHA and other areas that are environmentally sensitive or potentially at higher flood risk. These requirements, included in local floodplain management regulations, can take several different forms including:
Aside from or in addition to freeboard requirements or limitations on fill, local governments may wish to implement other regulations that reduce flood risk through drainage infrastructure and stormwater management requirements. For example, parishes and municipalities can implement provisions requiring best management practices, requirements that properties retain a certain additional percentage of runoff relative to pre-development conditions, or promulgate provisions requiring that nature-based solutions or other features are included to provide adequate water storage capacity to accommodate a certain storm-frequency event. Iberville Parish requires that new development provide drainage infrastructure sufficient to accommodate a ten-year storm event. For commercial, industrial, institutional and certain multifamily developments, St. Tammany Parish requires a certain percentage reduction of pre-development peak runoff relative to the 25- or 100-year storm event, depending on the overall development size in acreage (e.g., with parcels five acres or larger required to reduce runoff by 25 percent for a 100-year storm event with on-site detention ponds required).See footnote 26 Based on the best available science and data, Region Seven parishes and municipalities might consider how future conditions could affect design storm events and whether to incorporate these anticipated changes into stormwater and drainage regulations.
When considering the most appropriate and feasible ways to minimize flood impacts from new development, decisionmakers may find the following crosscutting considerations and practice tips useful:
These tips are based on priority implementation best practices and considerations most relevant to this specific objective and do not present an exhaustive list for regional and local planners and policymakers. In addition to this objective, decisionmakers should, at a minimum, also refer to Goal Five for crosscutting practice tips and considerations including the use of science and data related to flooding, drainage, and mitigation (Objective 5.2).
It is important to acknowledge that every jurisdiction will be starting from a different place and have a unique local context and needs, among other factors. Therefore, these practice tips could be adopted individually, collectively, or not at all. It will be up to policymakers to work directly with their communities and other key stakeholders and partners to assess and determine potential tools and approaches to implement this goal and objective.
The summaries below highlight resources and case studies available in Georgetown Climate Center’s Adaptation Clearinghouse that are relevant to this objective. They illustrate how many of the above benefits, practice tips, and planning, legal, and policy tools were or are being evaluated and used in practice in different jurisdictions. To learn more and navigate to the Adaptation Clearinghouse, click on the “View Resource” buttons.
Endnotes:
1. Fed. Emergency Mgmt. Agency, TECHNICAL BULLETIN 10-01: Ensuring That Structures Built on Fill In or Near Special Flood Hazard Areas Are Reasonably Safe From Flooding in accordance with the National Flood Insurance Program, 5–6 (May 2001), available at View Source. | Back to contentBack to content
2. 44 C.F.R. § 60.3 (2022). Back to contentBack to content
3. 44 C.F.R. § 60.3(c)(2) (2022). This standard also generally applies to new construction and substantial improvements of non-residential structures in the floodplain, unless designed so that any portion below the BFE is watertight with certain design components. Id. at § 60.3(c)(3). Back to contentBack to content
4. A 2017 analysis by CoreLogic found that in Louisiana, 49 percent of properties designated as “moderate” or “high” risk of flooding were located outside the SFHA, compared to 23 percent nationwide. 29 Million Flood Risk Properties Lie Outside Official Flood Zones: CoreLogic, Insurance J. (Dec. 6, 2017), View Source. | Back to contentBack to content
5. Freeboard, Fed. Emergency Mgmt. Agency, View Source (last visited Apr. 22, 2022). | Back to contentBack to content
6. NFIP’s Community Rating System (CRS) Class 8 Freeboard Prerequisite: Frequently Asked Questions, Fed. Emergency Mgmt. Agency (Nov. 2020), available at View Source. | Back to contentBack to content
7. 44 C.F.R. § 60.3(c)(2)–(3) (2022). Back to contentBack to content
8. 44 C.F.R. § 60.3(e)(4) (2022). Back to contentBack to content
9. Tangipahoa Parish La. Code § 36-287(1), View Source. | Back to contentBack to content
10. For more information on types of appropriate foundations in flood zones, see Shandy Heil & Patricia Skinner, Foundations in Flood Hazard Areas, LSU AgCenter (Jan. 6, 2007), View Source. | Back to contentBack to content
11. 44 C.F.R. § 60.3(e)(6) (2022). Back to contentBack to content
12. Georgetown Climate Ctr., Mexico Beach, Florida — Floodplain Ordinance 712, Adaptation Clearinghouse (2019), View Source. | Back to contentBack to content
13. St. Tammany Parish Land Use Code § 115-3 (9)(d), View Source. “Areas of special concern” are defined at § 115-3(8). | Back to contentBack to content
14. Jefferson Parish La. Flood Damage Prevention Ord. §§ 14-6.2.1–14-6.2.2, View Source. For new construction within Zone AE and outside the Hurricane Storm Damage Risk Reduction System, there is a two-foot freeboard requirement. Id. at § 14-6-2.1(3). | Back to contentBack to content
15. Fed. Emergency Mgmt. Agency, National Flood Insurance Program Community Rating System: Coordinator’s Manual 430-11–430-13 (2017), available at View Source. | Back to contentBack to content
16. The “regulatory floodway” refers to the “channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.” 44 C.F.R. § 59.1 (2022). The regulatory floodway is therefore a specific portion within the SFHA (floodplain) in which flood risks are much higher and strict prohibitions on development generally apply. Back to contentBack to content
17. See Fill, Fed. Emergency Mgmt. Agency, View Source (last visited Apr. 22, 2022). | Back to contentBack to content
18. Fed. Emergency Mgmt. Agency, TECHNICAL BULLETIN 10-01: Ensuring That Structures Built on Fill In or Near Special Flood Hazard Areas Are Reasonably Safe From Flooding in accordance with the National Flood Insurance Program 1 (May 2001), available at View Source. Such requests are referred to as Letters of Map Revision (LOMRs). | Back to contentBack to content
19. 44 C.F.R. § 65.5(a)(4)(ii) (2022). Back to contentBack to content
20. Fed. Emergency Mgmt. Agency, National Flood Insurance Program Community Rating System: Coordinator’s Manual 430-6 (2017), available at View Source. | Back to contentBack to content
21. 44. C.F.R. § 60.3(d) (2022) (“When the Federal Insurance Administrator has provided a notice of final base flood elevations within Zones A1-30 and/or AE on the community's FIRM and, if appropriate, has designated AO zones, AH zones, A99 zones, and A zones on the community's FIRM, and has provided data from which the community shall designate its regulatory floodway, the community shall: […] (3) Prohibit encroachments, including fill, new construction, substantial improvements, and other development within the adopted regulatory floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels within the community during the occurrence of the base flood discharge[.]”). Back to contentBack to content
22. Fed. Emergency Mgmt. Agency, National Flood Insurance Program Community Rating System: Coordinator’s Manual 430-7–430-8 (2017), available at View Source. | Back to contentBack to content
23. St. Tammany Parish Land Use Code §115-3(b)(2), View Source. | Back to contentBack to content
24. Fed. Emergency Mgmt. Agency, National Flood Insurance Program Community Rating System: Coordinator’s Manual 430-8 (2017), available at View Source. | Back to contentBack to content
25. Ascension Parish, Ascension Parish Master Land Use Plan 126 (May 2019), available at View Source. | Back to contentBack to content
26. St. Tammany Parish Land Dev. Code § 115-111, View Source. | Back to contentBack to content
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