Proposed Seawall Ordinance ULDR Section 47-19.3
Objectives 1. Scope of the Issues Addressed in the Ordinance Modification 2. Summary of Key Ordinance Modifications 3. Explanation of Proposed Seawall Elevation Requirements 4. Proposed Timeline of Public Meetings
2016 Current Seawall Ordinance Language Sec. 47-19.3. - Boat slips, docks, boat davits, hoists and similar mooring devices. (4)(f) The top surface of a boat slip, seawall or dock shall not exceed five and one-half (5½) feet above NGVD29, except when the adjacent property is higher than five and one-half (5½) feet above the NGVD29. (3.90 feet NAVD88) When above 5½ feet NGVD 29, the top surface may be of the same elevation as the average grade of the upland property abutting the seawall or dock and properties abutting either side of the upland property. Sets a Maximum Height.
2014 Marine Advisory Board Request Seawall Ordinance Language An ordinance change proposed • to the Marine Advisory Board in Spring of 2014. Following staff discussions, Mr. • Chappell agreed that the current ordinance was adequate to address future sea level rise for the useful life of new seawalls.
Seawall Elevations and Future Sea Level Rise Feet Above NAVD88 Mean Low Condition FT Tide 3.9 6.2 Max seawall height ( 5.5’NGVD29) 3.0 5.3 2 ft SLR -2060 1.0 3.3 Extreme high tide 0.0 2.3 Avg high tide (MHHW) 0.0 -2.3 Avg low tide (MLLW)
King Tide in September 2015 2.615 ft NAVD88 Observed King Tide Predicted King Tide Normal Hi tide
2015 Unified Sea Level Rise (SLR) Projection for SE FL • 3” SLR since 1992 Possible • 2030: 6- 10” SLR • 2060: 14- 26” Likely • Orange line for long term projects with low risk tolerance (2060: 34”)
Seawall Elevations and Future Sea Level Rise NAVD88 Feet Above Condition FT Mean Low Tide Proposed minimum 4.6 6.9 Sept 2015 Tide seawall height 2.6 ft 3.9 6.2 Max seawall height ( 5.5’NGVD29) 3.0 5.3 2 ft SLR -2060 1.0 3.3 Extreme high tide 0.0 2.3 Avg high tide (MHHW) 0.0 -2.3 Avg low tide (MLLW)
Miami, FL 240 events in 2045 Tidal Flooding today, in 2030 and in 2045 Southeast Florida will advance from <10 events today to 240 events in 2045
Existing Seawall and dock inundated ← Seawalls in significant disrepair →
Upland eroding through the seawall
Seawalls of differing heights offer different level of protection to the upland property.
Key Ordinance Modifications Adds definitions for seawall and for North American Vertical • Datum (NAVD88); Sets a minimum seawall elevation at 4.6 feet NAVD88; • Sets an allowable maximum height of the seawall based on a • property’s base flood elevation.; Requires seawall reconstruction to the minimum elevation if • the substantial repair threshold is triggered; Requires maintaining seawalls in good repair; • Addresses fixed and floating docks; and • Sets a date by which all seawalls must meet the minimum • elevation requirement (March 1, 2035)
Seawall Elevation Based on Base Flood Elevation (BFE) BFE = 4 or 5 ft NAVD88 • Min 4.6 ft - Max 5.0 ft • BFE= 6 ft NAVD88 • Min 4.6 ft - Max 6 ft • Not in a flood plain • Min 4.6 ft • Max Grade •
Proposed Ordinance Approval Timeline March - Ordinance April - Stakeholder Meetings (MAB – Apr 7, HOA reps, Seawall Contractors) May – Commission Conference (May 3) Public Reading: Planning and Zoning (May 18) Additional Stakeholder Mtgs (e.g. SAB) June - First Reading: City Commission (June 7) June/July - Second Reading/Adoption: City Commission (June 21 or July 12)
Questions
List of Stakeholder Meetings April 7 Marine Advisory Board April 14 Idlewyld Board of Directors April 17 Las Olas Isles Homeowners Association April 25 Council of Civic Association Executive Board May 3 Commission Conference May 10 Council of Civic Association Regular Meeting May 18 Planning and Zoning Board – Public Hearing May 23 Sustainability Advisory Board June 7 First Public Reading – City Commission June 21 Second Public Reading – City Commission
Minimum and Maximum Elevations Property’s FEMA Flood Minimum Maximum Insurance Rate Map Location Seawall Seawall Elevation Elevation In a floodplain, BFE >= 5.0 feet Base Flood elevation of the NAVD88 property In a floodplain, BFE = 4.0 feet 4.6 feet 5 feet NAVD88 NAVD88 NAVD88 Meet the definition In an X zone, not in a floodplain of grade
Estimated Costs of Seawalls • New Seawall • $1,230 per linear foot • Repair -e.g. broken/spalled concrete areas in the cap • $60 per cubic foot of epoxy mortar • Add a 12” cap to an existing seawall • $95 per linear foot
Neighbor Survey I have observed coastal water level increases I have observed increased flooding
Estimated Extent of Seawalls • Public Seawalls = 4 miles (21,120 linear feet) • Estimated cost for total replacement = $26 M • Estimated cost for adding a 12” cap only = $2 M • Private Seawalls = 191 miles (1,008,480 linear feet)
Virginia Key – January 2016 Observed tides continue to exceed predicted tides
Virginia Key – December 2015
Virginia Key – March/April 2016
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