City of Fort Lauderdale

Fort Lauderdale, FL, USA

An Overview Of Our Solution

The City of Fort Lauderdale, Florida, has over 300 miles of waterfront from its beaches, rivers, and canals. Many of its neighborhoods are at an elevation only a few feet above sea level. In December 2010, the City Commission approved a cost-share pilot program with Riviera Isles Homeowners Association (HOA) for a public-private partnership to address seasonal high tide events that were causing street flooding and property inundation. To prevent tidal waters from entering through storm drains, the HOA would pay the City to install one-way valves. If the valves proved to be effective in mitigating flooding, the City would reimburse the HOA. In 2011, the City installed 17 tidal valves into the stormwater system to prevent backflow, resulting in no observed incidences of salt water inundation above the catch basin grates during following seasonal high tide event. The City then reimbursed the HOA for its costs and began a program. To date, 20 additional tidal valves have been installed in other low lying locations and at least 52 more are planned for construction.

Who is this solution impacting?

Ecosystem

Urban/Built Environment

Community Type

Urban

Address

100 N. Andrews Avenue
Fort Lauderdale, FL 33301
美国

Email

ghadwen@fortlauderdale.gov

Hazard

Flooding

Identify the likelihood and frequency of this hazard

Tidal flooding is an annual event in low lying areas in South Florida caused by seasonal high tides, mainly in the fall. These flooding events can be exacerbated by strong easterly winds or the passage of tropical storms causing storm surges. According the 2014 publication “Encroaching Tides,” even under an intermediate low sea level rise scenario, today’s estimated six annual nuisance flooding events will increase to twenty-four events in 2030 and sixty-six events by 2045.

Explain how vulnerable the community is to this hazard

With over 300 miles of waterfront adjacent to the Atlantic Ocean, rivers, and canals, Fort Lauderdale is particularly vulnerable to coastal flooding. Tidal flooding affects high and low income properties, parks, and businesses. The City has over 10,000 parcels on canals with low lying adjacent streets. Broward County estimates that 166 acres in Fort Lauderdale are vulnerable with a one foot sea level rise (which is roughly equivalent to a current annual extreme high tide.)

List the potential affects of this hazard

Tidal flooding impedes traffic, closes roads, creates driving hazards, and limits vehicular and emergency vehicle access to low lying neighborhoods and business locations. Lack of access can impact business revenues, property values and the tourist economy. The saltwater water intrusion can damage property, landscaping, infrastructure and cause corrosion of cars. Flooding can cause repetitive insurance losses and raise insurance rates.

Identify how sensitive the community is to these affects

Projections are that the frequency of tidal flooding will quadruple in the next 15 years as sea level rise continues. Without interventions such as tidal valves, the current extent of flooding will continue impacting property values and the tax base at an exponential rate. The disruptive impacts of tidal flooding will only be amplified without mitigation efforts.

Preparedness Goal

Installing one way valves in the storm drains of vulnerable neighborhoods to reduce tidal flooding during high tide events

Implementation Actions

In 2011, the City of Fort Lauderdale installed 17 tidal vales in the Riviera Isles neighborhoods at a cost of $176,973. This reduced local seasonal flooding associated with extreme high tide events. Subsequently, an additional 20 valves were installed in other neighborhoods vulnerable to tidal flooding. The City continues to monitor and maintain these valves, removing debris quarterly. In addition due to the success of this program, the City plans to install 52 additional valves in 2015 and 2016 in locations with frequent flooding complaints. This solution effectively addressed season tidal flooding which directly impacts low lying neighborhoods and streets.

Describe Your Solution

Stormwater systems provide drainage during rainfall events moving rain water runoff from drains to an outlet. However, in a coastal community like Fort Lauderdale, during exceptionally high tide events, the stormwater systems in low lying neighborhoods may allow water to flow backwards through the piping system flooding the streets, neighborhoods, and businesses. This is most common during seasonal high tide events, known as “King Tide”, and typically occurs in the spring and fall of each year. During such events, vulnerable neighborhoods may often experience tidal flooding which can result in property damage, impassable roads, and closed businesses. In 2010, the City of Fort Lauderdale entered into a cost-share pilot program to install 17 tidal one-way valves in the stormwater systems of the Riviera Isles neighborhood. These valves restrict tidal waters from moving in the wrong direction, from outlet to drain. The valves can be inserted inline with the existing stormwater piping or placed at the system’s outlet. The City established performance criteria for this project which allows no salt water intrusion above the catch basin grates during non-rain events. The valves used in the cost share pilot program met the performance criteria. Consequently 20 additional tidal valves have been installed and many more are planned. It should be noted that these valves are only effective at reducing flooding that comes up the storm drain during high tides and would not reduce impacts of overland flow from storm surge.

Economic?

Installation of the tidal valves has reduced disruption of daily life for residents and tourists due to flooding events. This represents a significant benefit for residents. These valves contribute to maintaining property values and the City’s tax base. They reduce impacts of salt water on vehicles and infrastructure. Reduced flooding also helps prevent increases in insurance costs.

Environmental?

This project has reduced the frequency of salt water intrusion into the built environment and reduced the resulting damage to property and infrastructure. The valves prevent aquatic fauna from being conveyed and trapped on land. They also prevent saltwater from damaging residential landscaping.

What were the negative or unintended impacts (if any) associated with implementing this solution?

As a pilot project testing emerging technology and adaptation solution, this is a learning process. One of the challenges with the valves has been the associated maintenance costs. Accumulation of debris may impact the operation of the valves and shorten their useful life. To ensure that the valves are free of debris, the City cleans them quarterly. Design for installation should consider access to the valve for ease of regularly scheduled to ensure the effectiveness of the tidal valves. An additional concern is the perception that the valves will prevent all flooding. If a rain event occurs at the same time as a high tide event, the rain will cause flooding because the stormwater drainage system is blocked by the tide. The effectiveness of the valves has also created a greater demand for installation of the valves than the City can currently meet.

Return on Investment: How much did it cost to implement these activities? How do your results above compare to this investment?

In its first tidal valve project, in Riviera Isles, the City partnered with the neighborhood association to install 17 tidal valves at a total cost of $176,972 on this project. Additional costs (approximately $3,300 per year per valve) are incurred during the quarterly maintenance of the valves. However, these costs are only a fraction of the value of the homes impacted by the project. The neighbors see great value in installing tidal valves. Due to the success of this project, the City has installed another 20 valves with at least another 12 valves in planning stages.

What are the main factors needed to successfully replicate this solution

The most important factors for replication of this solution are (1) locations experiencing tidal flooding (2) a stormwater drainage system which can accommodate tidal valves and are readily accessible for maintenance (3) resources to pay for the valves and (4) dedicated resources to provide regular maintenance of the valves. These valves will only provide a benefit if a location is experiencing tidal flooding due to backflow through the stormwater draining system. These valves will not do anything to eliminate tidal flooding that can occur through any route (overland flow, breeching of a seawall) other than the stormwater system. In addition, the valves will fail if they are not regularly maintained. Debris can accumulate inside the valve blocking or damaging it. In addition, debris could accumulate in the pipe without maintenance hindering all drainage. Finally, the cost of the valves can exceed $10,000 per valve and may be prohibitive in some locations.

Overview

Problem

Results