Sea Level Rise Risk Assessment
Exploring potential sea level rise implications to and risk reduction for Anne Arundel County.
Introduction
Anne Arundel County, surrounded by more than 530 miles of shoreline, is vulnerable to increased flooding as a result of relative sea level rise (SLR).
In 2022, the County obtained National Oceanic and Atmospheric Administration (NOAA) grant funding from Maryland’s Department of Natural Resources (DNR) through its Community Resilience Grant Program to update the risk assessment in the 2011 SLR Strategic Plan .
These assessments provide recommendations for improving the community’s coastal climate resilience and addresses potential impacts to key sectors and assets:
- Loss of ecologically significant land
- Impacts on private properties and property values
- Impaired road access
- Impaired public utility infrastructure
- Private well and septic systems
- Damage or loss of archeological and cultural resources
- Impacts on the maritime industry
- Shoreline erosion
“The level of Chesapeake Bay water with respect to the land is now rising about three times as fast as it was during Colonial times, threatening more densely built communities and infrastructure that developed over the interim.” ( SLR Projections for Maryland 2018 (Boesch et al.): Page 1 )
The County recognizes that strategic planning for SLR will be an ongoing and evolving process as more research, analysis, and guidance becomes available. While the intent of this strategic plan is to identify steps that can be initiated by the County in both the near term and longer term, it is anticipated that this plan will be built upon and revised in future years.
As part of the ongoing effort to maintain the Plan, the County’s approach to updating the plan will use a multi-phase planning process:
Phase 1: Vulnerability & Risk Assessment
Present phase: Analysis and identify vulnerable and at risk areas and assets due to SLR
Phase 2: Feasibility Study of Potential Action
Future phase: Review feasibility of implementing proposed mitigation actions to protect vulnerable and at risk assets from SLR
Phase 3: Implementation of Priority Actions
Future phase: Implementation of mitigation actions following feasibility analysis
SLR within County Plans & Policies
The County is including SLR concerns into local planning and projects that build resilience and protect communities and public investments. Examples include the following:
Plan2040 , Anne Arundel County's General Development Plan
Plan2040 establishes a vision, goals, policies, and strategies to guide development of Anne Arundel County over the next twenty years. It lays out a policy framework that informs many of the County’s future decisions on land use, environmental protection, transportation, open space, agriculture, community facilities, historic preservation, housing, economic development, and quality of life. Plan2040 will be implemented through Region Plans, functional plans, design manuals, regulations, the capital budget, and the work programs of County departments.
The HMP focuses on mitigation strategies and actions that assess the vulnerability of coastal communities to SLR, coastal and nuisance flooding, and erosion. Coastal resilience strategies from this plan improve resilience of critical infrastructure to flooding and the impacts of climate change and identifies protective measures for cultural and historic resources.
Phase 1: Vulnerability & Risk Assessment
The 2011 SLR Strategic Plan includes the results of a vulnerability assessment completed to identify potential areas impacted by SLR and develop inventories of resources at risk. This assessment was based on models of 2 and 5 feet of sea level rise.
In 2023, this vulnerability assessment was updated utilizing new regional sea level rise scenario data from NOAA for 2050, 2065, and 2100. The 2023 planning effort included the development of a computer model that generated inundation maps for the new sea level rise scenarios. These maps allow users to identify areas at risk to flooding by simulating the effects of SLR based on highly detailed topographical elevations.
It is important to note that the 2 feet sea level rise inundation used in 2011 is similar to the 2050 sea level rise scenario used in 2023, which is 2.31 feet. Each new sea level rise scenario used in 2023 is provided in the table below.
Land and infrastructure which intersect the flood inundation boundaries for the 2050, 2065 and 2100 sea level rise scenarios were identified as at risk. Quantifying these impacts allows Anne Arundel County to better plan for building resiliency against these flood risks.
The application to the right displays the results of the inundation boundaries for each sea level rise scenario. This application is interactive and allows users to observe the flood depth at different locations, as well as review additional data provided by Anne Arundel County to locate vulnerable properties and infrastructure.
This static inundation model and vulnerability assessment was completed for all of Anne Arundel County. However, a more detailed investigation was completed for Region 9 (Mayo, Galesville, West River, Shady Side, Churchton, Deale, Tracy’s Landing and North Beach), due to the increased vulnerability for this region as identified in the 2011 Strategic Plan. In addition to quantifying impacted lands and infrastructure, the Region 9 study investigated FEMA HAZUS loss estimations for the 2050 sea level rise scenario plus the 1% storm event, social vulnerability as well as shoreline erosion. While this StoryMap summarizes the findings countywide, the results of the Region 9 study can be viewed within the 2023 Region 9 Coastal Resiliency Toolkit.
Land and Property Value
The 2011 SLR Strategic Plan stated nearly 2,200 acres of land are vulnerable under a 2-foot sea level rise. The 2023 analysis results indicated that over 3,100 acres of land are vulnerable to the 2050 sea level rise scenario. A total of 4,462 acres of land could potentially be impacted by the 2065 sea level rise scenario, however this amount nearly doubles when the inundation area is expanded under the 2100 sea level rise scenario.
Note: The 2011 and 2023 sea level rise scenarios differ in methodology and geographic extent. Therefore, although the data has been provided from the 2011 study, an exact data comparison could not be completed.
According to the 2011 SLR Strategic Plan, the total value of properties at risk to the 2 foot scenario was nearly $3 billion. Whereas the total value determined in the 2023 analysis for properties at risk the 2050 sea level scenarios was over $10.6 billion. Total assessment values for the 2065 sea level rise scenario was $11.4 billion, while the total assessment values for the 2100 sea level rise scenario were over $14.0 billion.
Principle Structures
According to the 2011 SLR Strategic Plan, 140 principal structures were determined to be vulnerable in the 2-foot scenario. A total of 167 principal structures were determined to be vulnerable in the 2050 sea level rise scenario for the 2023 planning effort. The majority of these are residential. Results increased to 699 principal structures for the 2065 sea level rise scenario, and a significantly greater increase to 4,270 principle structures for the 2100 sea level rise scenario. Of these, approximately 92% are residential structures.
Utility Infrastructure
Water lines within vulnerable areas are located all along the coastal areas, but there are small concentrations of sewer lines at risk in Glen Burnie, Green Haven, Pasadena, Severna Park, Gibson Island, and Edgewater.
Sewer lines potentially vulnerable to the new sea level rise scenarios are in the same location as the water lines, with additional areas of higher concentration in the Highland Beach area, Mayo, and Deale. The majority of sewer pump stations are at-risk to the 2100 sea level rise scenario and mostly located in Edgewater, Highland Beach area, Mayo, Shady Side, and Deale.
No public water or sewer treatment facilities are located in any of the new sea level rise scenarios.
Storm drainpipes are found in all of the sea level rise scenarios along the coastline. The 2100 sea level rise scenario potentially could have the greatest impact on the storm drainpipes.
Wells & Septic Systems
Individual septic systems in the County are susceptible to impacts of sea level rise, either due to surface inundation or to high water tables associated with a rise in sea level. This may cause septic systems to fail and can result in contaminated wells due to floodwaters and saltwater intrusion.
Septic systems on properties susceptible to the new sea level rise scenarios are primarily concentrated along the coastal portions of the Lake Shore peninsula, the Broadneck peninsula, Annapolis, and the coastal areas in South County including Deale/Shady Side peninsulas. Wells at risk are found in general in the same locations with septic systems at risk. These locations are consistent with the findings in 2011 SLR Strategic Plan.
Cultural Resources
Anne Arundel County is home to thousands of significant historic sites, archaeological sites, cemeteries, and Scenic & Historic Roads that warrant preservation. The County provides protections to these cultural resources through its Code (see Article 17-6-501 to 504). Over the centuries, human settlement has been focused on the shorelines and watersheds of the Chesapeake Bay, so hundreds of these sites are vulnerable to sea level rise. Documentation and survey efforts continuously add to the inventories of these sites.
Recommendations & Mitigation Measures
This section highlights areas of mitigation interest and recommended actions to reduce flood risk. Mitigation actions may be considered independently or combined to reduce risks under each priority.
Ecologically Significant Areas
Coastal ecosystems provide key functions including flood wave attenuation, coastal erosion protection, providing biodiverse habitats, and stimulating the local economy.
These priority sites serve to protect the coastal ecosystem from SLR, coastal flooding and shoreline erosion should be strategically developed to include contiguous shoreline property that includes public and private property. Recommendation and mitigation actions should be supported in the County’s Land Preservation, Parks and Recreation Plan.
Recommendations:
1. Continue and expand County efforts to restore living shorelines. Incorporate RSLR projections into design of these projects.
2. Expand outreach and education efforts for waterfront property owners and homeowner associations on shoreline restoration.
3. Increase funding and technical support for communities to design and implement living shoreline projects with a focus on areas at greatest risk of RSLR impacts.
Existing and Future Development
There are multiple mitigation measures that coastal communities are beginning to implement to protect existing development and minimize SLR risks to future development. These include structural measures, such as living shorelines and levees as well as policy changes, such as requiring houses to be built at higher elevations.
Recommendations:
1. Review and revise as necessary, County Code requirements and design standards for shoreline erosion control projects to require living shoreline techniques unless demonstrated to be infeasible and to establish design elevations that account for SLR.
2. Target flood-prone properties, including areas at risk from SLR as priorities for conservation easements or fee simple acquisition.
3. Review and evaluate potential changes to Planned Land Use and Zoning designations in areas at risk from SLR as part of Region Plans and Comprehensive Zoning.
4. Review development requirements in areas at risk from SLR as from SLR as part of update to County’s Critical Area program and amend relevant County Code sections as needed to implement recommendations.
Public Infrastructure – Transportation
Priority areas for road infrastructure mitigation measures consist of road segments in vulnerable areas where SLR would have the most severe impacts, potentially cutting off access to properties or neighborhoods. At risk public water and sewer infrastructure systems were also identified in vulnerable areas where future impairment would have the most severe impacts in terms of serving neighborhoods.
Recommendations:
1. Conduct feasibility study to prioritize roads and bridges for improvements to reduce flood risk and to evaluate the most effective design options.
2. Plan for appropriate maintenance and post-flood recovery for at-risk roads and bridges.
3. Develop evacuation plans for vulnerable peninsula areas during flood events
Public Infrastructure – Water & Wastewater Systems
The elements needed to ensure the ongoing operation of water and wastewater treatment systems are at high risk of damage. Post storm system components may need repair or replacement to bring the system back to full operation. It is important to identify these at-risk elements before a severe storm happens so that mitigation strategies can be developed and put into action to avoid or minimize storm damage and quickly restore service.
Recommendations:
1. Review pumping stations and discharge systems at County wastewater treatment plants to identify vulnerabilities to SLR and development and implement recommendations to increase resiliency.
2. Replace final effluent filter pumps at Annapolis Water Reclamation Facility.
Wells and Septic Systems
The Department of Public Works Our wAAter program is proactively engaging communities in septic problem areas to connect to public sewer or upgrade septic systems. This program should continue and include focused efforts in areas where SLR and rising groundwater will exacerbate septic problems.
Recommendations:
1. Continue to participate in regional efforts to monitor and protect groundwater resources, including monitoring of saltwater intrusion into aquifers.
2. Expand efforts to educate private well owners on flood risk and actions they can take to protect their wells.
3. Continue and expand technical and financial support for property owners to upgrade septic systems or connect to public sewer.
4. Evaluate the impact of increasing precipitation events and sea level rise on septic system function and develop strategies to ensure adequate percolation and functionality.
Historic and Archaeological Resources
Prioritizing cultural resources should be based on their significance and level of threat. Develop guidelines and requirements for the potential displacement of vulnerable historic resources when shoreline stabilization is not a feasible strategy for permanent protection.
Recommendations:
1. Review existing local laws and policies in order to strengthen protections and preservation assistance for endangered cultural resources.
2. Foster interdepartmental coordination during feasibility studies for coastal resiliency and adaptation between the Cultural Resources Section and other County departments, such as DPW and OEM.
3. Identify strategies for integrating historic site preservation and other cultural resource considerations with natural resource conservation through County shoreline protection projects and other resiliency plans and actions, including environmental monitoring.
4. Increase and prioritize survey, documentation, and preservation efforts on flood-prone areas, and provide for the support, staffing, resources, and financial means to conduct professionally-led emergency salvage archaeology/historic site documentation for significant sites.
5. Expand public outreach and education in floodprone communities to provide guidance on flood mitigation for historic structures, to establish volunteer site stewardship monitoring programs, and to encourage community investment into preservation actions for significant, endangered cultural resources.
6. Develop guidelines and requirements for the potential displacement and destruction of vulnerable historic resources and archaeological sites when shoreline stabilization is not a feasible strategy for permanent protection.
State/Federal Guideline References:
Critical Facilities
The loss of critical facility function has the potential to negatively impact communities because government and public service functions could be reduced or suspended during recovery stages. Ideally, communities will incorporate mitigation elements into renovations of these buildings before disasters occur to decrease impacts that floods and hurricanes could have on providing services to the public. However, if mitigation cannot be done before a disaster impacts a critical facility it should be incorporated during the repair process to make sure these facilities can withstand disasters in the future to allow communities to be more resilient.
Get Involved
Anne Arundel County is continuously working toward gaining a better understanding of flooding throughout the county to better inform future plans and policies.
YOU can help by reporting observed flooding in your local area.
How?
Through MyCoast: Maryland!
MyCoast is an app and website that uses photos to help track flooding caused by rain, storms, and other coastal events such as high tides. The app is free to the public and easy to use.
