This study is authorized by Title II. Section 201(a)(10) of the Water Resources Development Act of 2020 the study is authorized in accordance with the annual reports submitted to the Congress in 2019, pursuant to Section 7001 of the Water Resources Reform and Development Act (WRRDA) of 2014 (33 U.S.C. 2282d). The study was funded by the Disaster Relief Supplemental Appropriations Act of 2022 (DRSAA 22), (P.L. 117-43), Division B, Subdivision 1, Title IV, as a high-priority study of projects in States with a major disaster declared due to Hurricane Ida pursuant to the Robert T. Stafford Disaster Relief and Emergency Assistance Act (42 U.S.C 5121 et seq). 

Notwithstanding Section 105(a) of the WRDA of 1986 (33 U.S.C. 22 I 5(a)), which specifies the cost-sharing requirements generally applicable to feasibility studies, DRSAA 22 authorizes the Government to conduct the study at full Federal expense, to the extent that appropriations provided under the Investigations heading of the DRSAA 22 are available and used for such purpose. The Policy Guidance Memorandum on Implementation of Supplemental Appropriations of the DRSAA of 22 dated 25 April 2022, states that a new Feasibility Cost Share Agreement (FCSA) or an amendment to the existing FCSA is required to address use of DRSAA 22 Investigations funds at full Federal expense.

The FCSA was fully executed by all parties on 04 November 2022.

Generally, feasibility studies funded by DRSAA 2022 are conducted for not more than $3 million and are completed within 36 months, consistent with Section 1001 of WRRDA 2014. If a cost exemption is approved for a study, those additional costs may be funded from remaining supplemental investigations funds. On 26 April 2024, the Assistant Secretary of the Army (Civil Works) (ASACW) approved an exemption request in the amount of $280,000 and an additional 8 months.

The NFS is the State of Louisiana, acting by and through, the Coastal Protection and Restoration Authority Board of Louisiana (CPRA).  Learn more about CPRA here: https://coastal.la.gov/

The purpose of this study is to analyze alternatives to reduce flood risk as a result of riverine flooding within the Tangipahoa Parish, Louisiana study area.  The communities within Tangipahoa Parish, Louisiana are continually impacted by widespread riverine flooding from heavy rainfall events often associated with hurricanes and tropical storms. The Tangipahoa Parish has multiple sources of flooding (rainfall, riverine, coastal, interior/urban, and backwater); however, the scope of this study does not address coastal flooding from storm surge and waves, although coastal influences on river stages are reflected in the analyses.  The most recent flood events that caused major disruptions, damages, and economic impacts to the Parish included the 2016 Louisiana flooding and Hurricane Ida in 2021. In August 2016, the President issued a disaster declaration in Tangipahoa Parish and adjoining parishes due to impacts from “The Great Flood of 2016”.  The flood was responsible directly and indirectly for 13 deaths across all parishes (Louisiana Department of Health, 2023) and the rescue of at least 19,000 people (Louisiana National Guard Public Affairs Office, 2016).  Tangipahoa Parish experienced historic flooding to thousands of homes and businesses and impacts to the National transportation corridors, I-12 and I-55.  The flooding negatively impacted approximately 1,500 businesses and estimated 17,000 employees, which resulted in $17.4 million in lost labor productivity (Louisiana Economic Development 2016). Most recently, in 2021, Hurricane Ida damaged over 48,000 residential structures in southeastern Louisiana, causing $1.45 billion in damages.  The event brought catastrophic flooding damages throughout southeastern Louisiana and brought both localized flooding and riverine flooding throughout the Parish.

Tangipahoa Parish is in Southeast Louisiana and extends from Lake Maurepas and Lake Pontchartrain on the south to the border of Mississippi on the north.  Major communities in the study area include Ponchatoula, Hammond, Robert, Kentwood, and Tickfaw.

The study area supports a broad range of industries including distribution centers, truck farming, dairy farming, and the forestry industry. The study area also includes critical hurricane evacuation routes, including Interstates 12 and 55, as well as the Hammond Northshore Regional Airport and the Hammond Amtrak, which provide transportation to neighboring parishes and the New Orleans Metropolitan Area. Urban development is occurring in the study area and is expected to continue due to its proximity to the New Orleans metropolitan area and the I-12 and I-55 transportation corridors. Development is expected to convert agricultural and forested land to residential and commercial uses. 

The communities within Tangipahoa Parish, Louisiana are continually impacted by widespread riverine flooding from heavy rainfall events often associated with hurricanes and tropical storms. Flooding poses a significant risk to life safety and causes damage to residential and commercial structures.  The study area includes residential and commercial structures that have experienced damage and economic impacts caused by repeated flooding events.  The scope also includes analysis of impacts caused by coastal flooding, such as storm surge and waves, where there is overlapping risk of riverine and coastal flooding.  There is a small area in the southernmost portion of the Parish where this occurs.  

The Tangipahoa Parish Feasibility Study is authorized to investigate Flood Risk Management (FRM) problems and solutions associated with riverine flooding.  However, this study examines the coastal effects to identify problems associated with coastal surge and compound flooding.  Riverine flooding was examined by itself as well as with coastal effects accounted for.  This was done so the PDT could identify flooding from both riverine flooding and coastal surge for future consideration. The study included the riverine flooding effects from the Tangipahoa and Natalbany Rivers, and their tributaries, but did not address localized flooding in adjacent communities. Channels with discharges greater than 800 cfs for the 10% Annual Exceedance Probability (AEP) event (10 Year) flood event were included for consideration.

All of the objectives focus on problems and opportunities within the study area and within the 50-year period of analysis from 2033 to 2083.  The planning objectives for the study area include the following: 

• Objective 1: Reduce the risk to public safety associated with riverine flood impacts to residential and nonresidential structures, evacuation routes, and access to critical infrastructure.
• Objective 2: Reduce economic loss due to flood damage to structures (i.e., businesses, residential, commercial, and public structures) from riverine flooding.
• Objective 3: Reduce interruption of national transportation corridors, e.g., the I-12 and I-55.
• Objective 4: Increase community resiliency which is the sustained ability of a community to use available resources, before, during, and after riverine flooding events and/or coastal events.
• Objective 5: In conjunction with reducing flood risk and economic flood damages in the study area, incorporate the needs and considerations of all at risk communities.

USACE is currently requesting a policy exception from the requirement to recommend the NED plan and is currently identifying Plan 3b as the TSP.  If the policy exception is not granted, the TSP will default to Plan 1: Nonstructural NED Plan.

• Plan 3b (Total Net Benefits Plan) - The federal Recommended Plan is a comprehensive nonstructural flood risk management plan that includes a total of 1,088 structures Parishwide.  Approximately 1,006 residential structures would be elevated, and 82 nonresidential structures would be floodproofed to reduce flood risk. 
• Plan 1 (NED Plan) – This is the plan that accounts for areas of flooding that received the highest net NED benefits, when compared to the annualized cost, was selected for inclusion in the plan.  Plan 1 consists of the floodproofing or elevation of 597 structures across the Parish.

The study is in “Feasibility phase”, and working on feasibility level design of the plans above.  Additional analyses will be completed to refine and optimize the design and cost estimates of the measure. The revised design and costs will be incorporated into the numerical modeling (Hydraulics and Economics) to develop refined assessments of the performance and cost-effectiveness of the TSP, which will be included in the final Integrated Feasibility Report (FIFR) and final Environmental Assessment (FEA) as the Recommended Plan. The final report will fully describe the Recommended Action, as well as its costs, benefits, and consequences. Because uncertainty cannot be eliminated, the final report will further document the levels of certainty and the associated risks that are inherent in the assumptions and analyses.

waters. In recent years, though, the Corps also has begun to use many non-structural solutions.

Nonstructural flood risk management measures are proven methods and techniques for reducing flood risk and flood damages by adapting to the natural characteristics of flooding within the floodplain. In addition to being very effective for both short and long term flood risk and flood damage reduction, nonstructural measures can be very cost effective when compared to other flood risk management techniques.

Risk = f [(Probability of Flooding) x (Consequences)]

Probability of Flooding is the frequency of flooding or how often does flooding occur in a particular location.

Consequences are the potential life loss or damages associated with flooding. Structures (residential, commercial, critical, public, and industrial), land use (agricultural, urban, public), and infrastructure (highways, roads, rail, utilities) are the potentially damageable assets. Reduce the consequences of flooding and risk is reduced. Nonstructural measures are invaluable wherein the goal is to reduce flood damages without modifying the characteristics of the flood event.

Nonstructural flood risk management can be categorized as a set of physical or nonphysical measures utilized for mitigating loss of life as well as existing and future flood damages. The physical measures determined to be most commonly implemented are those which adapt to the natural characteristics of the floodplain without adversely affecting or changing those natural flood characteristics. Because of their adaptive characteristics to flood risk, wherein these measures support the National Flood Insurance Program as administered by FEMA and generally cause no adverse affects to the floodplain, flood stages, velocities, or the environment, these measures can be incorporated into existing or new structures to mitigate for potential future flood damages.

Nonstructural measures are permanent or contingent measures applied to a structure and/or its contents that prevent or provide resistance to damage from flooding.  Nonstructural measures differ from structural measures in that they focus on reducing the consequences of flooding instead of focusing on reducing the probability of flooding.

Flood Risk: Terms and Techniques:

https://www.iwr.usace.army.mil/Missions/Value-to-the-Nation/Flood-Risk-Mgmt/Flood-Risk-Terms-and-Techniques/

To learn more about Nonstructural Measures and Flood Risk Management visit USACE National Nonstructural Committee: 

https://www.usace.army.mil/Missions/Civil-Works/Project-Planning/nnc/

Click on the images for high resolution versions:

Questions or comments can be sent to:  TangipahoaFS@usace.army.mil