Proposed Seawall Ordinance ULDR Section 47-19.3 Objectives 1. - - PowerPoint PPT Presentation

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.

NAVD88 FT Feet Above Mean Low Tide Condition

3.9

(5.5’NGVD29)

3.0 1.0 0.0

• 2.3

6.2 5.3 3.3 2.3 0.0 Max seawall height 2 ft SLR -2060 Extreme high tide Avg high tide (MHHW) Avg low tide (MLLW)

Seawall Elevations and Future Sea Level Rise

King Tide in September 2015

Normal Hi tide Predicted King Tide Observed King Tide

2.615 ft NAVD88

Likely Possible

• 3” SLR since

1992

• 2030: 6-10” SLR
• 2060: 14-26”
• Orange line for

long term projects with low risk tolerance (2060: 34”)

2015 Unified Sea Level Rise (SLR) Projection for SE FL

NAVD88 FT Feet Above Mean Low Tide Condition

3.9

(5.5’NGVD29)

3.0 1.0 0.0

• 2.3

6.2 5.3 3.3 2.3 0.0 Max seawall height 2 ft SLR -2060 Extreme high tide Avg high tide (MHHW) Avg low tide (MLLW)

Sept 2015 Tide 2.6 ft

Seawall Elevations and Future Sea Level Rise 4.6

6.9

Proposed minimum seawall height

Tidal Flooding today, in 2030 and in 2045 Southeast Florida will advance from <10 events today to 240 events in 2045

Miami, FL 240 events in 2045

Seawalls in significant disrepair

→

Existing Seawall and dock inundated

←

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)

• 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

Seawall Elevation Based on Base Flood Elevation (BFE)

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)

Proposed Ordinance Approval Timeline

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 Insurance Rate Map Location Minimum Seawall Elevation Maximum Seawall Elevation In a floodplain, BFE >= 5.0 feet NAVD88

4.6 feet NAVD88

Base Flood elevation of the property In a floodplain, BFE = 4.0 feet NAVD88 5 feet NAVD88 In an X zone, not in a floodplain Meet the definition

• f 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