The City of Miami Beach has approximately 55 miles of seawalls of which approximately 50 miles are privately owned, and 5 miles are City-owned.
The City of Miami Beach has reconstructed approximately 1 mile of seawalls, 0.2 miles of seawalls are currently in the design phase, and an additional 1 mile of seawalls are either under construction or under procurement to be constructed. The remaining 2.8 miles of City-owned seawalls require reconstruction.
The Public Works Department has developed a 10 year prioritization list for the reconstruction of the remaining 2.8 miles of City-owned seawalls. Factors such as elevation, location, condition of each seawall were used to develop the initial ranking of each seawall.
The initial rankings were then adjusted to capture the benefits derived from contiguous private seawalls segments. By optimizing the elevation of public seawalls adjacent to extended private seawall segments, the City can mitigate additional flooding and encourage residents to reconstruct their own seawalls. The public seawall prioritization is the first step to establish a continuous storm surge and overland flooding barrier throughout the City. Utilizing the elevation data that was collected for all public and private seawalls, staff will work with private property owners to communicate future flood risk and vulnerability. Staff will also be revisiting discussions with financial institutions that could potentially assist private property owners with financing.
Additional details on each of the ranking factors are provided below.
Public Works performed a topographical survey of all seawalls within the City. The survey was performed using an Unmanned Aerial System (UAS), colloquially known as a drone, equipped with state-of-the-art Light Detection and Ranging (LiDaR) technology to determine the ground elevations. This data was analyzed to distill the mean seawall elevations and lengths for all public and private seawalls.
Adjustments were made to the initial rankings to consider the location of each seawall. Seawalls located parallel to emergency evacuation routes, such as Indian Creek or Dade Boulevard, were ranked higher than those located at street ends or residential neighborhoods.
In 2011, a comprehensive seawall assessment was completed which evaluated all public seawalls for structural integrity, likelihood of failure, and its criticality. This assessment was validated in 2015 by a visual structural inspection. Based on these findings, the City reconstructed about 1 mile of seawalls that were considered critical and in poor structural condition.
The initial rankings for the seawall prioritization were also adjusted to account for critical seawalls determined to be in poor structural condition. The seawall prioritization should be adjusted accordingly following periodic future structural assessments.
The benefit of elevating public seawalls must account for contiguous private seawall segments adjacent to the public seawall being elevated. This is especially true for those areas where the public seawall is at a relatively low elevation compared to the private seawalls. Thus, the prioritization exhibited included higher rankings for those seawalls where additional benefits can be realized from extended private seawall segments.
Based on planning level estimates, the ten-year public seawall reconstruction program requires a total budget in the amount of $48.5M, $21M of which has been fully funded. An additional $5M is expected in FY 22 from the budget cycle and another $5M in FY 23 from G.O. Bond. This results in a funding gap of $17.5M. Below is the anticipated expenditure schedule for the total $48.5M:
· FY21 $1.5M
· FY22 $16.3M
· FY24 $7.1M
· FY26 $9.9M
· FY28 $6.8M
· FY30 $6.9M
The $48.5M includes $38.5M for the 2.8 miles of seawalls as depicted on the seawall priority map. It also includes the following: $1.5M for the 0.2 miles of seawalls in design, $5M for the remainder Indian Creek Drive seawall and $3.5M for two seawall projects currently under the process of procurement.
These estimates remain planning level estimates (AACE 56R-08 Class 5) until verified by the engineer of record during the design process.
The ten-year public seawall reconstruction program was presented to the Land Use and Sustainability Committee and Finance and Economic Resiliency Committee members at their September 14, 2021 and September 24, 2021 meetings respectively. Both received favorable recommendations to proceed to the next City Commission for approval.