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Flood Protection Level of Service

 

Program Overview

To fulfill the need of long-term flood protection for basins throughout the 16-county region, a flood protection level of service (FPLOS) program has been established. The mission of this program is to identify and prioritize long-term infrastructure improvement needs, and to develop an implementation strategy to assure that each basin can maintain its designated FPLOS, in a technical and cost-effective manner, in response to population growth, land development, sea level rise and climate conditions change.

Level of Service Flood Studies General Map

 

                                                        Figure 1.  Priority Basins for FPLOS Studies in the SFWMD

Flood Protection Level of Service Program

The SFWMD is implementing the program at a regional and local scale (Figure 2). Regionally, the SFWMD has developed a prioritization of basins to study (Figure 1), a methodology and suite of tools for evaluating structures and canals in selected watersheds, and a framework for establishing the level of service. 

The program incorporates input from meetings and workshops with local planning and stormwater management efforts, stakeholders, and resource managers. The FPLOS will be implemented in a phased approach in a 10-year cycle. Each basin will be evaluated, and actions taken as necessary on a 10-year cycle, to ensure that the level of service is maintained.

When remediation is needed, the lowest cost measures will be undertaken first, building to full replacement only when necessary. The cycle will provide opportunities to update development and sea level information and incorporate new technology and tools. This cyclic approach is the best use of funding and ensures that incremental, near term measures will be incorporated into any long-term solution.

 

fplos overview chart 

                                              Figure 2. Flood Protection Level of Service Program Overview

 

Program Phases

Within each basin, the program has three phases. Phase 1 consists of assessing the level of flood protection provided by existing infrastructure under current and future development and sea level scenarios. 

Calibrated flood models of the basin are used to evaluate basin conditions using performance measures. Phase 1 efforts are completed in cooperation with local stakeholders to help identify flooding issues and gather additional data.

 

Flood Protection Performance Metrics

presentation slide image

The SFWMD has developed six (6) FPLOS performance metrics (PMs) to quantify the level of flood protection provided within a watershed now and in the future.  Four of these measures (PM 1-4) assess performance of the regional drainage systems. PM 5 and 6 assess impacts to local flooding frequency and duration within the communities that these drainage systems serve.

Depending on the metric, the PMs may consider three scenarios: the system’s original design, the current condition of the system (existing scenario), and a range of future sea level and rainfall conditions (future scenarios).

Future scenarios may also include predicted land use changes, operational changes, and water use changes. Two of the metrics (PM1 and PM2) evaluate the future stages and capacity of the canal reaches. Two of the metrics (PM3 and PM4) evaluate conditions at the downstream structure (applicable only to tidal structures). And the last two performance measures (PM5 and PM6) evaluate the future impacts to flooding. Further explanation of the six (6) FPLOS PMs are found by clicking on the graphic.

More detailed descriptions of these measures can be found in the following report:

South Florida Water Management District, 2015. Flood Protection Level of Service Analysis for the C-4 Watershed. Appendix A: LOS Basic Concepts. H&H Bureau, the District, West Palm Beach, FL. December 2015.

PM 1:Maximum stage in primary canals. PM 1 determines the peak stage profile along the primary canal system for design, existing, and future conditions. If stages are above design levels, the ability to drain the adjacent communities is reduced.  Further, if water levels exceed the height of the canal banks, overbank flow could cause localized flooding.

PM 2: Maximum daily discharge capacity through the primary canals.  PM 2 determines the flow capacity of the primary canal systems throughout the District for design, existing, and future conditions. The flow capacity of the canal reaches will be assessed with respect to the capacity yielding no adverse impacts.

PM 3: Tidal structure flow performance – effects of sea level rise. PM 3 determines the effect of sea level rise on the discharge capacity of tidal structures.  This evaluation will be based on structure design features and existing operational protocols.

PM  4: Peak storm runoff - maximum conveyance capacity of the watershedPM 4 determines the flows passing at the downstream structure under future conditions. Future scenarios will consider the combined effect of storm events, sea level rise, and storm surge averaged over the tidal cycle (for tidal structures).

PM 5:Frequency of flooding – stage based LOS for sub-watersheds. PM 5 determines the overall ability of the water management infrastructure to maintain water levels within communities.  This PM will consider the upper limits of flood stages and depths of water needed to protect the local infrastructure such as homes, commercial buildings, and major roads.

PM 6 Duration of flooding– effects of sea level rise.  PM 6 determines the time required for water levels to recede to non-flood stages for storm events under future conditions. 

Where problems are identified, Phase 2 studies identify potential flood mitigation projects and prioritize project implementation. Locations are identified within the basin where the level of service has diminished to the point that a change is needed. 

Remediations may include, in order of complexity and expense, improvements to operations, improvements to canal conveyance, improvements to secondary drainage features, and refurbishment or replacement of flood control structures. Nonstructural strategies such as land-use change may also be assessed. The Phase 1 and 2 assessments provide key elements for Adaptive Resilience Planning.

Phase 3 of the program is to implement the selected and approved mitigation strategies upon approval by the District Governing Board.  The activities in this phase include developing a prioritized list of steps required, coordinating with other District programs, developing a schedule for completion that incorporates time lags needed to implement solutions, and designated current and future funding requirements.

Adaptive Resilience Planning

Because of uncertainties of future development and sea level rise, an Adaptive Resilience Planning (Figure 3) approach is used to implement improvements in three steps, as potential future risks are identified. The first step is to initiate non-structural and operational changes to reduce the extent and duration of flooding. 

The second step is to monitor conditions over time and measure against established thresholds for infrastructure refurbishment or replacement. The last step is to initiate refurbishment or replacement of facilities when the process determines that the required flood protection level of service will no longer be met.

When initiating refurbishment or replacement of facilities, it is often not the most responsible approach to build projects based on the worst-case projection. An approach that allows incremental improvement without precluding future changes to address the worst-case projections will be more acceptable and more likely to be implemented.  A key element of Adaptive Resilience Planning is constructing infrastructure that can be readily adapted in the future as additional mitigation is needed.

An example of adaptive infrastructure at a stormwater pump station would be installing pumps sized for the current tailwater condition but sizing the wet well and discharge pipes to accommodate a larger stormwater pump in the future.

 

presentation slide image                                                                            Figure 3. Adaptive Resilience Planning

Progress to Date

In 2016, the SFWMD completed the first phase of the FPLOS study in the C-4 Basin in Miami-Dade County. In 2017 and 2018, Phase 1 and Phase 2 studies of the C-7 Basin and the Big Cypress Basin were completed, and Phase III projects have been identified.

In 2019, Phase 1 studies of the C-8 and C-9 Basins are underway. In Broward, Lee and Osceola counties, stormwater and flooding investigations are being completed by county agencies in cooperation with the SFWMD that will later lead to Phase I FPLOS studies by the SFWMD (Figure 4). 

SFWMD flood protection map

                                        Figure 4. Flood Protection Level of Service Phase 1 and Phase 2 Studies

Looking Forward

The process being undertaken by the SFWMD to understand the current and projected level of service of flood protection infrastructure is critical to maintaining flood protection for the region. This SFWMD effort only addresses the primary system of State and Federal owned infrastructure. 

Effective basin management requires cooperation and input from local governments and other agencies to prioritize and fully implement solutions. Many municipalities across the State are conducting similar evaluations through stormwater management master plans. 

The FPLOS process provides a helpful planning tool for prioritizing and designing projects in the secondary and tertiary systems. The FPLOS program ensures a flood control system resilient to shocks and stresses such as hurricanes, floods and droughts. 

The studies will cover the entire District every 8 to 10 years and are estimated to cost about $2 million a year. Mitigation project development will cost an additional $2 million a year. Making the changes to the infrastructure will cost between $30 and $70 million a year over the next two decades.

Most importantly, identifying future flood protection issues at the local and regional level is only the first step.  Funding and constructing the necessary mitigation measures is the most critical piece. The FPLOS program provides information to policy makers and taxpayers about the impacts of flooding and the importance and timing of funding effective solutions.