sea level wise: comprehensive sea level rise …...2020/03/11 · sea level wise: comprehensive sea...
TRANSCRIPT
SEA LEVEL WISE: Comprehensive Sea Level Rise and Recurrent Flooding StudyVirginia Beach Adaptation Strategy Report
C.J. Bodnar, PE and Sue Kriebel, PEPublic Works – Stormwater Engineering CenterMarch 11, 2020
Agenda
• Project Overview• “Sea Level Wise” Adaptation Strategy Report
• Part I – Introduction• Part II – Understanding Flood Risks• Part III – Adaptation Framework• Part IV – Watershed Strategies• Part V – The Path Forward
• Next Steps
2
Project Overview
3
“Sea Level Wise” – Timeline of Activities
4
2015 2016 2017 2018 2019 2020
Planning• Scenarios• Conceptual
model
Study Progression• Grant award• Hazard and risk
assessment• Essential analysis to
inform design• Stormwater coordination• Policy menu
Strategy Focus• Structural Alternatives
o Conceptso Performanceo Down-selection
• Policy refinement and rankings• Neighborhood and site alternatives
Synthesis• Full Draft Adaptation Strategy Report
Finalization• Stakeholder
outreach and input
• Conclude NOAA Grant
• Feasibility and continued implementation
Informing Design• Rainfall/surge correlationo >50% of rainfall events occur during elevated water levels
• Joint-probability of rainfall/storm surgeo Concurrent rainfall/surge design values
• Regional Precipitation Trendso Atlas 14 outdatedo Heavy rainfall increasing, 20% needed over design life cycle
• Probable maximum event precipitationo Design “check storm”
• Wind Tides o Water level response to wind tide conditionso Minimum design tailwaters
5
Stormwater Design Standards
6
“Sea Level Wise” Adaptation Strategy Report
7
“Sea Level Wise” Adaptation Strategy Report
What is the purpose? • Summarize work activities in a unified framework• Present a wide range of potential adaptation
initiatives• Relate strategies across the City’s diverse
watersheds• Provide high-level implementation timeline for
potential projects• Identify additional research needs
8
How is it structured?
9
PART I PART II PART III
PART IV PART V
IntroductionPART I
10
Introduction
11
• A Call to Action:• Observed Flooding Issues
• Becoming Sea Level Wise• Program Phases• Community Engagement• Regional Connections
Public Engagement
12Community Meeting Locations across the City of Virginia Beach
Understanding Flood RisksPART II
13
14
Complex Flooding Pathways
West Neck Creek
Rudee Inlet
Lynnhaven Inlet
Back Bay
North Landing River
Elizabeth River Southern Branch
Elizabeth River Eastern Branch
Little Creek Inlet
Understanding Flood Risks
15
• The Challenges of Rising Sea Levels • Sea Level Rise Scenarios • Recurrent Flooding• Storm Surge Flooding
Range of Federal Projections Observation-based Projections by VIMS
Understanding Flood Risks
16
• Compounding Factors• Coastal-Rainfall Flooding• Urban Development • Aging Infrastructure• Groundwater Changes• Ecological Decline
• Flooding Impacts• The Cost of Inaction• Where are Losses Occurring?• Physical Damages• Indirect Economic Impacts• Social Implications
Future Distribution of Loss
Cost of Inaction
Adaptation FrameworkPART III
17
Multiple Layers of Adaptation
18
Prepared Communities Adapted
Structures Engineered Defenses
Natural Mitigations
Preserve Environmental Assets
Increase Natural and Nature-Based Features
Pursue an Expansive Defense Network
Regulate Building and Development
Support Risk-Mitigating Interventions
Minimize Infrastructure Vulnerabilities
Grow Educational Outreach
Promote Economic Resilience
Integrating Policy and Planning
19
o Comprehensive and strategic planning
o Budgeting and financingo Community outreacho Building codes and standardso Partnerships
o Research and analysiso Land use planning and zoningo Incentives and support
programso Program and project
management
How? In order to achieve those outcomes, the City can employ a number of policy and planning tools:
Envisioning an Adapted Virginia Beach
20
(City-wide)
Natural Mitigations
21
Preserve Environmental Assets
22
Protect and expand green infrastructure networks through land conservation and renaturalization programs.
Protected and unprotected green spaces
throughout the City
Voluntary Acquisition
Conservation Easements
Land Conservation Techniques
Development Rights Purchasing
Strategic Growth Areas
Setback and Buffers
23
Increase Natural FeaturesInvest in the restoration, enhancement, and construction of natural and nature-based infrastructure that provide flood protection benefits.
Areas for the restoration and
creation of nature-based
features
Beaches and Dunes
Marshes
Maritime Forests
Seagrass
Shellfish Reefs
Living Shoreline Ecological Revetments
Non-Structural Protections
Structural Protections
Engineered Defenses
24
25
Pursue an Expansive Flood Defense NetworkInvest in the long-term construction of a structural defense network that provides wide-reaching protection from increasingly severe coastal flood risks.
“City-wide” Alternatives
Inland Structural Defenses
In-Water Structural Defenses
Neighborhood-Scale Structural Systems
26
Advantages As compared to city-wide…• Relatively quick to design and construct• Relatively less expensive • Protects from high-frequency floods
(tidal, nuisance, small storms, etc.)
Disadvantages • Inadequate flood protection against
hurricane storm surges • Often not compatible with City-wide
options
CharacteristicsWest of Lesner Bridge
East of Lesner Bridge
RudeeHeights
Sandbridgeand Sigma
Muddy Creek Road
Alignment Length (ft) 5,970 10,510 North - 3,300
South – 900 28,730 48,130
Reduced Floodplain (acres) 225 523 North – 79
South – 1,406 5,395 7,644
Structures Protected 637 1,268 North – 185
South - 220 2,782 695
Approx. Costs(Millions - 2018) $15.8 $35.5 $10.8
(combined) $61.3 $72.2
Project Benefits * $30.5 $61.3 $39.8 $323.3 $222.8
Adapted Structures
27
Regulate Building & Development
28
Require responsible siting, design, and construction practices for new and substantial redevelopment that are reflective of the area’s current and future flood risks.
Floodplain Ordinance Update
Coastal Zone Creation
First Floor Elevation Requirements
Critical Facility Location Conditional Permitting
Siting and Design Regulations
Priority areas for restricting, regulating,
and encouraging development.
Support Risk-MitigatingInterventions
29
Provide resources and incentives to encourage flood-resilient design or retrofits on residential and commercial properties.
Priority areas for supporting risk-
mitigating interventions at the
parcel-level
Dry FloodproofingWet Floodproofing Structure Elevation
Mitigation-Reconstruction Voluntary Acquisition Green Infrastructure
Loan Program
Flood In. Rate Reduction
Fee Reductions
Property Tax Relief
City Funded Grants
Federally-Funded Grants
Site-Scale Mitigation Methods
Financial Incentives and Assistance
Minimize Infrastructure Vulnerabilities
30
Engage with local and regional infrastructure and utility agencies to better understand independent and cascading vulnerabilities and make proactive investments.
Critical infrastructure
networks
Prioritized Asset Investments
Resilient Construction Standards
Operations and Maintenance
Cross-Jurisdictional Collaboration
Public-Private Coordination
Regional Commitment
Infrastructure Management Techniques
Prepared Communities
31
32
Grow Educational OutreachDevelop programs and tools to inform vulnerable residents about their flood risk and facilitate access to mitigation, preparedness, and recovery resources.
Educational Workshops
Business Outreach
Community Partnerships
Consultation Services
Community Flood Science
Public-Facing Resources
Engagement Methods Economic Resilience TechniquesFlood Insurance
ExpansionCommunity Rating
ImprovementCultural Asset
Protection
Military Coordination
Agricultural Preservation
Green Job Growth
Promote Economic ResilienceBolster flood resiliency of the City’s economic engines through access to planning resources, technical guidance, and financial support.
Watershed StrategiesPART IV
33
Watershed Approach• Each watershed has distinct
flooding challenges and opportunities
34
Lynnhaven
Oceanfront
Elizabeth River
Southern Rivers
Elizabeth River7%
Lynnhaven74%
Southern17%
Oceanfront2%
Elizabeth River4%
Lynnhaven48%
Southern45%
Oceanfront3%
Today 3 ft Sea Level Rise
Applying the Adaptation Framework
35
Lynnhaven
Elizabeth River
Oceanfront
Southern Rivers
Adaptation Vision
• Natural Mitigations• Living Shoreline• Marsh Restoration and
Creation• Land Conservation
• Adapted Structures• Building Elevation• Commercial
Floodproofing• Floodplain Regulation• Responsible
Development• Infrastructure Resilience
36
• Engineered Defenses
• Elizabeth River City-wide Alignment
• Prepared Communities
• Residential Community Education
• Flood Insurance Expansion
• Business Outreach and Education
ELIZABETH RIVER WATERSHED
Adaptation Vision• Natural Mitigations
• Beach and Dune Nourishment
• Ecological Revetments• Land Conservation• Living Shoreline• Marsh Restoration and
Creation• Shellfish Reefs and Oyster
Restoration• Seagrass Restoration
• Engineered Defenses• Chesapeake Bay
City-wide Alignment• West and East of Lesner
Neighborhood Alternatives37
• Adapted Structures• Building Elevation• Commercial
Floodproofing• Floodplain Regulation• Responsible
Development• Infrastructure Resilience
• Prepared Communities• Residential Community
Education• Flood Insurance
Expansion• Business Outreach and
Education
LYNNHAVEN WATERSHED
Adaptation Vision
38
OCEANFRONT WATERSHED
• Natural Mitigations• Beach and Dune
Nourishment• Ecological Revetments• Land Conservation• Living Shoreline• Marsh Restoration and
Creation• Shellfish Reefs and
Oyster Restoration
• Engineered Defenses• Atlantic Oceanfront
City-wide Alignment• Rudee Heights
Neighborhood Alternative
• Adapted Structures• Building Elevation• Commercial
Floodproofing• Floodplain Regulation• Responsible
Development• Infrastructure Resilience
• Prepared Communities• Flood Insurance
Expansion• Business Outreach and
Education
Adaptation Vision
39
SOUTHERN RIVERS WATERSHED
• Natural Mitigations• Beach and Dune Nourishment• Ecological Revetments• Land Conservation• Living Shoreline• Marsh Terrace Creation• Seagrass Restoration
• Engineered Defenses• West Neck Creek City-wide
Alignment• Sandbridge City-wide Alignment• Muddy Creek Road City-wide
Alignment• Sigma and Muddy Creek Road
Neighborhood Alternatives
• Adapted Structures• Building Elevation• Commercial
Floodproofing• Floodplain Regulation• Responsible
Development• Infrastructure Resilience
• Prepared Communities• Flood Insurance
Expansion• Business Outreach and
Education
The Path ForwardPART V
40
Planning and Coordination• Continued City Response Efforts • Planning Processes and Frameworks
• Comprehensive Planning• Hazard Mitigation• Military Collaboration and Planning• Transportation Planning • Emergency Operations Planning• Capital Improvement Programming• Operations Budgeting• Strategic Planning• Strategic Growth Area Master Planning• State Coastal Planning
41
Next Steps• Council Review and Public Comment
• Completed February 28, 2020• Council Adoption of Sea Level Wise Adaptation Strategy Report
• Planning Commission Briefing – March 11, 2020• Planning Commission Public Hearing – April 8, 2020• City Council Briefing and Public Hearing – May 5, 2020
42
Discussion
43