2025 Maine Sustainability & Water Conference

Thursday, March 27, 2025
Augusta Civic Center
Augusta, Maine

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Session B – Flood Assessment and Recovery

Morning Session
Presenters are indicated in bold font.

Session Co-chairs:
Sam Roy, Supervisory Physical Scientist, U.S. Geological Survey, sroy@usgs.gov
Sarah Jamison, Senior Service Hydrologist, National Weather Service, sarah.jamison@noaa.gov

Multiple agencies and nongovernmental organizations in Maine bring an array of expertise and resources to flood assessment and recovery leading up to and following riverine and coastal floods in the state. With increasing extreme-weather events, expanding development, and persistent funding challenges, bringing awareness to this expertise and to available resources is crucial. For this session, agencies, water resource professionals, data managers, and citizens are invited to come together to discuss the best available science that we can bring to flood response, assessment, and mitigation. We welcome discussion of innovative riverine and coastal flood modeling and mapping tools that can be used in the context of a changing climate; trends in flood risk, occurrence, and impacts; the state’s Hazard mitigation plan, mitigation grants, and other funding mechanisms; and platforms and education for citizens to access these tools and resources.    

Session Schedule

Morning Session

8:30AM – 8:55AM
Stream Smart Culverts: From Prioritization to Design

Marc Chmura, GEI Consultants Inc., MChmura@geiconsultants.com
Joel Bilodeau, GEI Consultants Inc., JBilodeau@geiconsultants.com

Replacing undersized culverts with environmentally friendly and climate resilient Stream Smart Culverts can reduce flooding, enhance stream health, and improve aquatic connectivity for fish and wildlife. However, these culverts can be costly and selecting which ones to prioritize can be difficult. 

To address this, GEI has developed a process to help communities identify culverts for replacement using readily available data from trusted sources including the Nature Conservancy and Maine Department of Inland Fisheries and Wildlife. Our methodology scores and ranks culverts based on a range of criteria including flood risk, environmental benefits, economic significance, emergency response, and other factors. This system enables regulators to allocate resources effectively and strengthen grant applications by demonstrating the suitability of proposed Stream Smart Culvert replacements.

Once a culvert is selected for replacement, hydrologic and hydraulic (H&H) modeling is often one of the first steps in the design process. The level of modeling effort can vary, ranging from simple StreamStats flow estimates to watershed-wide 2D hydraulic modeling. Stream Smart Culverts are typically designed to accommodate the 100-year storm, but existing utilities, roadway elevations and other constraints can make large culvert installations challenging. Additionally, increasing the size of one culvert can sometimes exacerbate flooding downstream. Therefore, hydraulic modeling is crucial to demonstrate reductions in overall flood risk, climate resiliency, and ensure project feasibility. 

Our presentation will discuss possible ways to prioritize culvert replacement projects and the types of H&H models available that can be used for watershed planning and the design of Stream Smart Culverts.

9:00AM – 9:25AM
Stream Flood Vulnerability Assessment at Acadia National Park

Ian Armstrong, U.S. Geological Survey, New England Water Science Center, iarmstrong@usgs.gov
Meghan Mccallister, U.S. Geological Survey, New England Water Science Center, mmccallister@usgs.gov
Kristina Labrie, U.S. Geological Survey, New England Water Science Center, klabrie@usgs.gov
Adam Benthem, U.S. Geological Survey, National Geospatial Program, abenthem@usgs.gov

Acadia National Park (ANP) has experienced increases in the frequency and magnitude of precipitation in recent years, leading to increased flood flows, amplified stream erosion, and costly infrastructure damage. To prioritize safe, economic, and resilient infrastructure management in the wake of a changing climate, the U.S. Geological Survey, in cooperation with the National Park Service, has prepared tools that allow natural resource managers tools to identify culverts and stream reaches most susceptible to erosion and flood damage within ANP. To develop these flood-risk management tools, we first created an elevation-derived hydrography based on a 1-meter Digital Elevation Model, and then estimated flood flows along the stream and culvert network using Maine regional regression equations. We measured geomorphic and hydrologic features, such as stream steepness, channel incision, and percent storage in contributing watershed to assess erosion vulnerability and compared computed flood flows to culvert conveyance capacities to assess culvert vulnerability. We combined the erosion and culvert vulnerabilities in an interactive ArcGIS Dashboard map and database. Initial results indicate that the majority of stream reaches and culverts located in the high-gradient, incised headwaters of the ANP highlands, such as Sargent Peak, Penobscot Peak, and Cadillac Mountain, contain the highest relative erosion and flood damage vulnerability, and generally coincide with past erosion and infrastructure damage. These relatively quick and cost-effective tools can be applied in any region where high-resolution lidar, flood-flow regional regression equations, and culvert data are available.

9:30AM – 9:55AM
Understanding flood impacts by combining community observations and real-time water level data

Anna Simpson, Northeastern Regional Association of Coastal Ocean Observing Systems, anna@neracoos.org
Gayle Bowness, Gulf of Maine Research Institute, gayle@gmri.org
Stephanie Sun, Gulf of Maine Research Institute
Sienna Zuco, Gulf of Maine Research Institute
Hannah Baranes, Gulf of Maine Research Institute
Jamie Carter, NOAA Office for Coastal Management
Tom Shyka, Northeastern Regional Association of Coastal Ocean Observing Systems

Ocean monitoring systems play a critical role in preparing for, responding to, and recovering from hazards associated with coastal flooding. The Northeast Regional Association of Coastal Ocean Observing Systems (NERACOOS) works with a network of partners from the Gulf of Maine to Long Island Sound to produce, integrate, and deliver critical coastal water level data to support local decision making efforts. NOAA’s National Weather Service (NWS), for example, uses the data to validate predictive models and issue local flood watches and warnings. 

These data also support community information needs. The Gulf of Maine Research Institute (GMRI) works closely with NERACOOS to pair coastal water level monitoring data with community science. This approach presents a unique opportunity to collaborate with and learn from coastal residents by connecting real-time data with local knowledge.

GMRI’s Coastal Flooding Community Science Project collects data from residents, including weather conditions, photos of flooding, and community perspectives. Combined with real-time data, communities are able to relate precise water level measurements (12.5 feet MLLW, for example) with their observations of flood impacts, and community members are able to report their level of concern and preferred adaptation solutions. The resulting data and information help inform both immediate emergency preparedness efforts and long-term climate adaptation strategies.

Through this collaborative project, individuals, communities, and municipal officials alike can build knowledge about local water levels and associated flood impacts in their communities and play an important role in gathering data to support climate action and flood preparedness.

10:00AM – 10:25AM
Characterizing the December 18-21, 2023 Flood in Maine

Amanda Tudor; U.S. Geological Survey, atudor@usgs.gov
Sarah Jamison, Senior Service Hydrologist, National Weather Service, sarah.jamison@noaa.gov

The U.S. Geological Survey (USGS) in cooperation with the Federal Emergency Management Agency (FEMA) is conducting a study characterizing the magnitude and extent of the December 18-21, 2023 Flood in Maine. A slow-moving rain event on December 17-18, 2023, produced 4-8 inches of precipitation and up to 4.5 inches of meltwater from residual snowmelt, resulting in catastrophic flooding. In response, the USGS collected over 350 high-water marks in Maine that document the peak water-surface elevation of the flood; in some cases exceeding elevations collected during the April 1987 Flood in Maine. The USGS is documenting and analyzing these high-water marks as well as computing flood frequencies, assessing the accuracy of FEMA Flood Insurance Studies, and determining if reservoir storage played a role in the intensity of the flood. Preliminary flood frequencies were calculated for 59 streamgages in Maine that were affected by the flood. Thirteen of those streamgages exceeded the 100-year recurrence interval streamflow. These data are useful for assisting in future flood recovery efforts and guiding mitigation practices. Finalized data will be available through a USGS Scientific Report, a USGS Data Release, and an online interactive ArcGIS StoryMap.