Rising Waters

Managing Floodplains in the Northeast in an Uncertain Future

Poor Creek Photo, Petersburg National Battlefield , May 2024

Shaded forest scene with a small, shallow stream running through an eroded gully. The gully has steep, moss-covered banks with exposed roots and soil layers. Sunlight filters through the dense canopy of green leaves, casting dappled light on the forest floor and water.

Here we summarize survey results and translate the findings into easily accessible resources for NPS asset managers, helping them better understand and address flood and erosion risks.

What is a hydrologic hazard?

  • A hydrologic hazard is any extreme water level or flow condition occurring within the floodplain. ​
  • These hazards can cause impacts like erosion, scour, and infrastructure damage to NPS lands, wild and scenic rivers. 
  • Credit: NPS / Jacob W. Frank, July 18, 2022.

What is a floodplain?

A floodplain is a flat area of land adjacent to a river or waterbody that periodically floods. Floodplains are vital in absorbing and slowing floodwaters, improving water quality by filtering pollutants, recharging groundwater, and providing critical habitats for wildlife. They offer natural flood control and support biodiversity but can pose risks if developed improperly.

How do you know if your  project is in a floodplain? 

Floods adversely affect infrastructure, threaten cultural and natural resources, and compromise visitor safety.

Climate change also impacts flood frequency and magnitude.

Road washout near Gooch Gap, Blue Ridge Parkway - milepost 336 NPS after Hurricane Helene.

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Overview of Flood Risk Management Concerns

First, we surveyed resource and facilities managers in the Northeast to assess the impacts of floods and droughts on parks. The survey focused on current challenges, planning strategies, and the tools needed to better manage these hazards, with an emphasis on inland rivers and floodplains.

Click on this slideshow to view the survey results.

The survey identified key issues impacting parks and park-supported areas. For Natural Resources, the primary concerns were channel erosion, scour, or sediment deposition, followed by flooding and low flows.

Regarding Safe Recreation, the main challenges included erosion or scour of nearshore facilities, unsafe flows for boaters and swimmers, and flooding of nearshore facilities. These findings highlight the significant impact of water flow dynamics on both natural systems and recreational infrastructure.

Main hydrologic issues

  • Around 80% of survey takers identified flooding as an issue at their park​
  • Around 85% of survey takers identified erosion, scour, and deposition as an issue at their park​
  • Low flows were are also noted by many survey takers as a problem, especially for natural resources and recreation areas.

Floodplain management

Key floodplain management questions focused on determining whether facilities were in floodplains, deciding on floodproofing or relocating existing facilities, and ensuring new facilities avoided flood-prone areas. Additional concerns included managing erosion, planning for higher river flows, and reconnecting rivers to floodplains, emphasizing the need for actionable steps to address risks at the time.

Low flow management

Key management questions for low flow conditions focused on whether extreme low water levels caused irreversible damage to aquatic and wetland habitats and how poor water quality impacted resources and visitor experiences. Other concerns included the navigability of waterbodies, loss of visitor days, and ensuring accessibility for boat ramps and access points. Write-in responses emphasized visitor safety during variable flows and flooding.

Flood risk tools Survey respondents identified several tools they use to assess flood risk:

  • FEMA flood insurance maps were the most commonly used, cited by 50% of respondents.
  • National wetlands inventory and aerial/satellite images were each used by 42% of respondents.
  • Landscape topography and institutional knowledge or oral history were each used by 33%.

These findings highlight the variety of tools available for evaluating flood risk, emphasizing that the choice of tools depends on the specific problem being addressed and the resources available.

Our survey results regarding the clarity and implementability of five different federal flood risk management and climate adaptation guidelines found that:

Across all documents, the dominant trend is lack of familiarity, as indicated by high percentages of unread guidance. Among those familiar with the guidance, perceptions vary, with relatively few finding them fully clear and implementable without additional guidance. There is a consistent need for additional support, training, or clarification to improve implementability.

Our results show that a majority of respondents have not read the guidance documents, with the Federal Flood Risk Management Standard (73%) and DOI Guidelines on Flood Adaptation (60%) having the highest unread rates. Among those familiar, clarity is generally limited.

The most commonly used guidance documents for floodplain management are  DO 77-2/PM 77-2  and NPS Planning for a Changing Climate, while the FFRMS is the least used, with some respondents relying on other resources or none at all.

Policy & Guidance Resources

Understanding and mitigating flood and erosion risks require adherence to established policies and best practices. Below are key resources from FEMA that provide essential guidance for asset managers:

Federal Emergency Management Agency (FEMA) – Information on disaster assistance, emergency preparedness, response and recovery activities etc. 🔗  Explore FEMA 

FEMA National Flood Insurance Program (NFIP) – Learn about flood insurance and risk management strategies. 🔗  Visit NFIP 

Flood Risk Communication Toolkit – Guidance on effectively communicating flood risks. 🔗  Explore the Toolkit. 

Hazard Mitigation Assistance (HMA) Programs – Funding opportunities for flood risk mitigation. 🔗  Learn About HMA Grants 

These resources offer valuable tools and frameworks to support decision-making in flood and erosion risk management.

The project will include information on three case study parks, allowing for tailored content that addresses the specific hydrologic management needs and conditions at each location. You can view the case studies  here. 

  • Petersburg National Battlefield (PETE): A dedicated StoryMap will focus on erosion and scour challenges unique to this site.
  • Valley Forge National Historic Park (VAFO): This StoryMap will address flood and erosion risks relevant to the park’s historical and natural landscape.
  • New River Gorge National Park and Preserve (NERI): A StoryMap for this park will cover broader hydrologic challenges affecting its diverse ecosystem.