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District Operations

SOUTH BROWARD DRAINAGE DISTRICT OPERATIONS

This is a summary of the stormwater management system and stormwater operations of the South Broward Drainage District (SBDD).

SBDD’s jurisdictional boundaries encompass 46,600 acres (approximately 73 square miles) in SW Broward County. These limits extend from Griffin Road to the north; the Broward/Miami-Dade County line to the south; US 27 to the west; and N 72nd Avenue to the east. SBDD’s stormwater facilities include 150 linear miles of canals, 7,700 acres of lakes, thousands of inter-connecting drainage culverts (pipes), 7 primary stormwater pump stations, 2 secondary stormwater pump stations, 12 flood control gates, and 19 real- time water level recorders. SBDD staff is able to monitor and operate its systems on 24-hour/7-day basis through a state-of-the-art telemetry system. SBDD’s equipment and facilities are tested and maintained on a regular basis to ensure that the system is functional and ready to operate when needed. SBDD’s primary pump stations are fully automated, whereby the pumps are programmed to start automatically based upon permitted flow rates and elevations. All of SBDD’s primary pump stations are equipped with emergency generators to ensure continuous operations, even during power outages. Whenever possible, SBDD performs its major maintenance work during the dry season (December – April).

The primary role of SBDD is to help protect properties from flooding. SBDD has a Criteria Manual which regulates drainage requirements for new construction, redevelopment, and all works within SBDD easements and rights-of-ways. SBDD’s regulations are aimed at finding a balance between flood protection, water quality, and water conservation. In addition, SBDD performs limited maintenance of the water bodies throughout the district with the main focus on ensuring the proper, unimpeded flow of stormwater through the system. During the rainy season, SBDD’s focus is on its major facilities – stormwater pump stations, flood control gates, major equipment, canals, and culverts.

The primary means of flood protection in South Florida is the ability to store rainwater and stormwater runoff in low-lying areas or “storage areas”. These storage areas consist of lakes, canals, swales, retention areas, and other low-lying areas. Lakes are the most effective and efficient means of providing storage for flood protection.

Every community in SBDD (and Broward County) is required to provide a minimum volume of stormwater storage in order to protect its community from flooding. In addition, each community will have its own internal drainage system, which is comprised of drainage inlets (catch basins), inter-connecting pipes, swales, lakes, retention areas, and other facilities. Together, these facilities are known as the “tertiary drainage system”. The responsibility for maintaining and operating the tertiary system usually falls upon the Homeowners Association or local municipality.

The requirements and capacity of the tertiary system is determined by professional civil engineers who perform drainage calculations and stormwater modeling to determine the amount of storage (lakes) that is needed to protect those communities from flooding during major storm events. Each community’s drainage system is required to provide sufficient storage for flood protection, and the primary means for meeting these storage requirements is within the internal lakes. SBDD requires that all of the lakes within the tertiary system be inter-connected with pipes or culverts. This will allow the stormwater within the overall system to “equalize” and allow the entire community to benefit from the storage capacity in the tertiary drainage system.

The tertiary system will then connect to SBDD’s drainage system, which is known as the “secondary drainage system”. These connections are almost always made with culverts. As noted above, SBDD’s system consists of a series of canals, inter-connecting culverts, stormwater pump stations, and flood control gates. Stormwater moves from the tertiary systems, through SBDD’s infrastructure, and is eventually released into one of two state-maintained canals. These two canals (C-11 to the north and C- 9 to the south) are operated by the South Florida Water Management District (SFWMD) and receive all permitted stormwater runoff from SBDD. Due to the fact that these two canals serve all of the communities that border the canals, the rate of discharge into these canals is strictly regulated by the state. Thousands of acres of properties rely on these state-managed, primary canals for flood protection, so it’s critical that the volume of water that flows into these canals is regulated to allow adequate storage and conveyance for all the communities and properties that rely on them. It is SFWMD’s job to ensure that the capacity is available for these communities when it’s needed; and SFWMD does an excellent job of operating and managing these canals.

SBDD is divided into 13 large drainage basins which manage and control discharge into the C-11 and C-9 canals. With a few minor exceptions, all of the properties north of Pines Boulevard flows north into the C-11 Canal and all of the properties south of Pines Boulevard flows south into the C-9 Canal. Each of SBDD’s drainage basins has a surface water management permit issued by the state that regulates the total amount of “storage” within each basin, and rate of discharge from each basin into either the C-11 Canal or the C-9 Canal. SBDD’s stormwater pump stations and flood control gates have been designed to provide the maximum, “allowable” discharge from each drainage basin.

SBDD is required to operate its facilities in accordance with the drainage permits that are in place for each individual drainage basin. SBDD does not have the authority to operate its pumps or flood control gates outside the limits of these permits.

Each individual drainage basin has a “Control Water Elevation” (CWE) that has been established by permit. SBDD operates and manages its system to try and always maintain water levels at the CWE. During the dry season (Dec – April), SBDD’s gates and pump stations will typically be closed in an effort to conserve water, and keep the lake levels from falling too far below the CWE; and during the rainy season (May- Nov) SBDD will operate its gates and pump stations in an effort to maintain lake levels as close as possible to the CWE, and provide maximum storage for flood protection. During the dry season, SBDD is not able to “recharge“ or pump water back into the system to raise lake levels.

As noted above, SBDD’s system is part of the overall water management and flood control system for the community. It’s a three-tier system that consists of the tertiary system (community lakes and internal drainage system); secondary system (SBDD canals, culverts and gates); and primary system (SFWMD C-11 and C-9 Canals). All three systems work together to provide drainage and flood protection for a community.

The primary facilities for flood protection are the lakes and storage areas within each drainage basin. SBDD manages and operates its flood gates and primary canals to provide for the maximum allowable (permitted) discharge through the system. SFWMD operates and manages its canals and pump stations to ensure that SBDD’s system has the ability to discharge into the receiving body of water at the highest flow rates possible, given all of the variables that may occur during any given rain event.

During a major storm event, SBDD’s stormwater management system operates in the following manner:

  • Prior to a major rain event such as a tropical storm or hurricane, SBDD will coordinate with SFWMD on the status of the regional stormwater network and weather forecast.
  • SBDD will be managing its system to maintain water levels at the low range, which is the CWE.
  • SFWMD will very often give SBDD and other local drainage districts permission and authority to begin lowering water levels below the CWE in advance of the storm; and SBDD will begin to lower water levels to the lowest elevation authorized.
  • As the rain event starts, stormwater begins to collect within the tertiary drainage system and flow into the lakes and storage areas.
  • The lakes begin to rise as more stormwater runoff drains into the lakes.
  • The majority of the internal lakes are inter-connected, which allow the lakes to equalize across the tertiary system.
  • At the same time, stormwater is flowing “out” of the tertiary system and into SBDD’s system through a series of outfall pipes. The flow rate “out” of the system will be limited by the capacity and size of the outfall pipes.
  • During a major rain event, the capacity of the outfall pipes will be far less than the volume of water coming “into” the system (rainfall).
  • SBDD is continually monitoring the storm and operating its system to allow for the maximum flow rate “out” of the system.
  • SBDD’s stormwater pump stations are fully automated and programmed to operate when the water levels reach a predetermined elevation. These predetermined elevations are set by permit. SBDD is not authorized to start pumping before the water levels reach these elevations.
  • The lakes and storage areas within the system are providing the primary means and capacity to store water and prevent flooding.
  • The more rainfall that occurs, the higher the lakes will rise.
  • SBDD will be moving as much water as its system is capable of moving, based upon the regulated (permitted) discharge rates, along with the physical constraints of the canal system, inter- connecting culverts, and capacity of the pumps.
  • The levels of the receiving waters (C-11 Canal and C-9 Canal) also play a role. The higher these canals stage, the less capacity SBDD has to discharge and lower its waters.
  • Typically, major rain events tend to be “regional” events whereby, the entire South Florida region is experiencing the same intensity and volume of rainfall. And since all these communities are sharing and draining into the same receiving waters, those canals will also begin to rise as the storm continues to drop more and more rain.
  • SBDD coordinates with water managers from SFWMD during the storm to share information and verify SFWMD’s systems are operating at full capacity as well.
  • Once the storm passes, the overall system will begin to “recover” and the water levels will begin to recede. It may appear that the lakes are receding at a very slow rate; however, the system is actually draining a large volume of water out of the system; typically between 50,000 gallons per minute (GPM) and 140,000 GPM.
  • The goal is always to recover and lower the water levels back down to the CWE before the next major storm event.

There are several factors that affect the rate in which the lake levels recede, including, but not limited to, the following:

  • The total amount of rainfall, which dictates the total volume of water that needs to be moved through the system.
  • The overall size of the drainage basin that needs to be drained. SBDD’s drainage basins typically cover over 5,000 acres of land; and SBDD’s system is working to lower all of the lake levels within the entire basin. For a major storm event this will equate to a tremendous volume of water.
  • All of the lakes within a drainage basin are inter-connected with pipes; and so during and after the storm, the lakes are “equalizing”, which means that the lakes with higher elevations are flowing into lakes with lower elevations in an effort to achieve equilibrium. This may give the appearance that certain lake levels are not receding in the initial time period after the storm ends, but in reality, the system is moving as much water out as the system can handle, and the internal lakes are “equalizing” during that same time period.
  • The capacity of the overall system to discharge water (canals and inter-connecting pipes).
  • The total length of the canals and culvert systems (Pines Blvd to Griffin Rd; or Pines Blvd to the County Line).
  • The water levels in the C-11 Canal and C-9 Canal, which are SBDD’s receiving bodies of water. The lower the water level in the C-11 and C-9 Canals, the more water SBDD can discharge into them.
  • The weather. Additional rainfall will increase the total volume needed to discharge.

In summary, the overwhelming majority of the communities in SBDD have an excellent drainage and water management system with a tremendous capacity to store stormwater for flood protection. In addition, most of SBDD’s drainage basins have stormwater pump stations, which allows SBDD to pump water out of the system, even when the tail water is elevated. This has proven to be a tremendous benefit to SBDD’s residents over the years.