Community pond weir

Weirs Are Weird But Needed

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In coordination with the South Florida Water Management District permit, the Lake Worth Drainage District (LWDD) allows two types of discharge control structures in residential communities and commercial properties – Operable and Non-Operable. The labels Operable and Non-Operable do not pertain to the structure’s ability to provide flood protection, but rather identify the type of structure and the way it is designed to function.

Non-Operable Structures, also known as ‘passive structures’, typically have an overflow weir or a triangular “bleed down” orifice installed at the stormwater pond’s designed water-control elevation. These overflow orifices allow the gravity flow of water through the structure and into drainage canals until the pond water rests at the designed water-control elevation. Given its passive nature, water will flow through the structure virtually any time there is rainfall except during very dry conditions when pond levels are lower than the water-control elevation.

So, why are there Operable Structures? A series of normal rain events can sometimes raise the level of the stormwater pond faster than the Non-Operable Structure can remove the water. The Operable Structure includes the passive flow described above, as well as a vertical slide-gate with an operating mechanism (usually a hand-wheel) that can be manually opened or closed to control the rate of water flow from the pond to drainage canals. The Operable Structure can be opened to manually lower the pond elevation after a rain event or before major weather systems like tropical storms or hurricanes.

It is important to note that the Operable Structure can only be opened with permission from LWDD. Sometimes that permission is granted at the request of an individual community or business. However, more often LWDD will give blanket permission to all communities and businesses based on forecasted weather conditions. In those situations, LWDD will provide notification by email and give a specific time to operate the Operable Structure. Communities and businesses can register designated representatives to receive these notification emails as well as find additional information and guidelines for the operation and maintenance of structures at https://lwddnet.wpengine.com/property-managers-hoa.

LWDD is the only drainage district in the State of Florida that allows Operable Structures.  It requires close coordination with local and regional authorities, but we believe it provides flood control benefits to the residents living within the LWDD boundaries.

1900's photo of dredge in canal

The Orrin Randolph Plan

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The Lake Worth Drainage District (LWDD) was established on June 15, 1915, with a three-member Board of Supervisors whose mission was to reclaim land within its boundaries. Prior to the creation of LWDD, a considerable amount of drainage work had already been completed by several entities such as the State of Florida, the Palm Beach Farms Land Company, the Model Land Company, and the Boston & Florida Atlantic Coast Land Company. In addition, private landowners and farmers had dredged drainage canals throughout the area. Although small drainage systems had been created, a cohesive long-term drainage plan was needed for the future expansion of what is now known as Palm Beach County.

In the spring of 1916, Orrin Randolph, Chief Engineer for the newly created LWDD, presented his first report to the Board of Supervisors. This report contained 127 pages detailing a plan of means and methods for draining the lands within the boundaries of LWDD. The report was submitted in compliance with Chapter 6458 of the 1913 Session Laws of the State of Florida. At that time, LWDD consisted of 129,317 acres of land and 3,400 acres of water. Rectangular in shape, LWDD extended 26 miles in length and 8 miles in width. Population records of 1916 showed there were approximately 6,500 owners of property within LWDD’s boundary making the average ownership equal to 20 acres per capita. Approximately 400 farmers were cultivating an estimated 5,000 acres of land, principally vegetables for distribution to northern markets.

In his report, Orrin Randolph identified the areas within LWDD that could not safely be relied upon for agricultural purposes and outlined the design parameters needed for future drainage. Randolph stated, “Provisions for artificial drainage would absolutely be necessary in order to provide a run-off rapid enough to prevent the destruction of crops as a result of accumulated excess water on the land.” Thus, Randolph’s extensive report was adopted by the Board of Supervisors as the Plan of Reclamation. The implementation of this plan would forever change the local landscape.

South Florida’s abundant agricultural resources served as the catalyst upon which prosperous and populous cities were built. This prosperity, then and now, is a result of the water management plan introduced by Orrin Randolph and adopted by LWDD over a century ago as the Plan of Reclamation. This plan created a large network of drainage canals providing flood control and water supply which remarkably still functions today for over 800,000 residents and tens of thousands of acres of farmland.

Agriculture in our area no longer exists to only feed the local inhabitants, and the migration of people into Florida continues to increase annually. LWDD has modified its mission over the century to meet the changing water management needs of these two diverse communities. Much of the District’s emphasis today is on residential flood protection. Although meeting the needs of agriculture and settlement can bring many challenges, it is because they harmoniously co-exist that living and working in our community is so highly desirable.

golden retriever dog in rain boots holding an umbrella

How Flood Control Works

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Man-made stormwater ponds are attractive enhancements to many residential communities and businesses within the Lake Worth Drainage District (LWDD). More importantly, these waterbodies serve an important public safety purpose as they are part of the overall flood control system.

When it rains stormwater flows into the retention pond and, if needed for flood control, out through the pond’s discharge control structure into the LWDD canal. Most of the time this drainage occurs unnoticed by the average individual. However, during a severe storm, flooding in streets, sidewalks, and driveways may occur. This temporary flooding may cause concern, but it is important to note these low-lying areas are designed as secondary detention areas to protect buildings and homes from flooding.

Within LWDD’s boundary, flood control is a shared responsibility and achieved through an interconnected, 3-tiered drainage system governed by 3 unique groups of people. Through communication and coordination, these 3 groups can provide effective flood control. The groups are identified as:

  • Neighborhood drainage systems operated by property owners or residential associations
  • Secondary drainage systems operated by LWDD or municipalities
  • Primary regional system operated by the South Florida Water Management District

Water managers in charge of primary and secondary systems are continually monitoring the weather and canal levels to proactively respond to changes in canal elevations. In anticipation of a heavy rainfall event, water managers will make operational adjustments to maintain appropriate water elevations for flood control. Additionally, throughout the year routine canal maintenance is conducted to provide unobstructed flow in the canal channel and access along the canal rights-of-way. The inspection of control structures, pumps and other infrastructure is also conducted, and repairs or replacements are made.

Property owners and residential associations have a similar role regarding their neighborhood drainage system. They must maintain their drainage infrastructure to ensure that inlets, storm drains, underground pipes, and emergency discharge control structures are free of potential blockages and working as designed, thus maintaining the flow of stormwater away from their property. An annual inspection of the drainage infrastructure should be made, and repairs should be completed before the onset of storm season.

LWDD works closely with property managers and community boards to manage potential flooding. You can find more information about flood control at https://lwddnet.wpengine.com/storm-response.

Men looking a set of blueprints

Potential Impacts of Sea Level Rise on Water Management

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Excerpt From South Florida Regional Compact Implementation Guidance Series 2021

As the sea level continues to rise in response to the changing global climate, south Florida will become more and more susceptible to a wide variety of negative effects, primarily due to its very low topographic elevation. While the effects of sea level rise on coastal communities in south Florida are being reported worldwide, the more subtle impacts to the regional water resource management system, have recently come to light. The impacts fall into three general areas:

  1. Flood protection and drainage systems
  2. Quality of existing underground water supply sources
  3. Natural systems already impacted by human activity

The first, and most obvious impact is to the overall drainage system which in virtually every case ultimately releases excess stormwater into the ocean through the coastal estuaries. These systems are almost exclusively gravity driven. This means that water flows from higher elevations on the landscape to lower elevations simply by allowing gravity to pull the water from one drainage feature (swale, ditch, canal, pond, etc.) down to another until it finally flows into the ocean at the lowest level. When the ocean elevation rises, the elevation difference between upland areas and the ocean is lessened, which in turn lessens the gravitational pressure to move large volumes of rainfall runoff out to sea. This effect ultimately reduces the flow of water through the structure and slowing it down and increasing the frequency and duration of flooding resulting from heavy rains.GraphicThe path that stormwater takes from its beginning as runoff from heavy rains to its release into the ocean, is managed by a series of numerous physical structures made up of pipes, gates and sluices. These structures are operated (opened or closed) in conjunction with one another to release water from developed areas to avoid flooding or hold it back to enhance water storage and groundwater recharge.

Slow drainage problems are amplified when coastal structures are hit with a heavy rainfall event which is typical during land-falling tropical storms and hurricanes. In these cases, the elevation of the storm surge downstream of a structure (ocean side) can be pushed above the water level in canals upstream (land side). In these situations, the system operational personnel have no choice but to close the water control structure to avoid the inland rush of the coastal storm surge into the canal network, thereby further worsening flooding impacts.

Regional coastal structures maintain groundwater levels, which hold back saltwater intrusion into underground freshwater aquifers; they are also critical to minimizing flooding impacts. But numerous communities downstream of these facilities do not directly benefit from their operation yet face the same threat to their drainage infrastructure. The cities of Miami, Miami Beach and Fort Lauderdale are key examples of this situation.

Sea level has risen about eight inches over the past 100 years, and there are clear indications from recent tidal data that the rate of rise is accelerating. This forces immediate attention on the regions, like coastal south Miami-Dade County, where the current water control elevations are already very close to the current range of tidal fluctuations.

Most of the major water control structures along the coastline in Miami-­‐ Dade County already maintain canal elevations very close to the upper end of the normal tidal elevation range. In some cases, spring tides already exceed the normal canal elevation, which forces gate closures at least twice a day during those periods.

Similar situations exist in Broward County, where numerous communities and their local drainage systems are situated downstream of the regional water control system. These communities find themselves in the position of facing a double threat associated with flooding. They are threatened by both direct impacts of rising seas on their local drainage systems, and storm discharges from the western regional systems flowing through the canal systems in their communities. A simple solution would be to stop or reduce the releases from the western communities. However, this action would most certainly worsen flooding in those towns and cities.

Adaption strategies can be complicated and expensive but must be considered for future implementation Statewide. For more information on the response to sea level rise, visit  https://southeastfloridaclimatecompact.org.

Water Flows Downhill: But Not Always In the Desired Direction

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Stormwater management systems within the Lake Worth Drainage District (LWDD) area are required to provide both flood control and water quality mediation. There are two general types of stormwater systems that perform these functions – retention and detention. Both systems depend on proper grading of the land to successfully keep homes from flooding and ensure water quality. The relationship between land and stormwater management is inseparable.

swale area filled with water arrows are indicating the direction water will enter the swaleA retention stormwater system is designed so the grading or slope of the land helps to collect water in low lying areas. This helps to prevent flooding in undesirable areas and allows the water to slowly seep into the shallow groundwater aquifer. As the stormwater seeps into the ground, the grasses, sand, soils and rocks help filter out contaminants thus providing water quality treatment. The retention stormwater system can be man-made or a naturally occurring depression. There is no discharge to another water body such as a pond, lake or canal. This type of drainage system is often found in rural areas or large undeveloped areas.

Community lake with arrow indicating where the water will flow into a drain and then outflow to the lakeA detention stormwater system is used by most modern-day residential communities. The design directs and contains stormwater onsite in a pond. It is designed to allow pollutants in the water to settle to the bottom of the pond leaving cleaner water on top. Again, the grading of the landscape is vital to the success of the system as the water must flow toward and into the detention system. The detention system consists of pipes and catch basins to collect and direct the stormwater. Water moves away from homes via an overland drainage flow. Front, side, and back yards typically utilize overland drainage. Stormwater flows through the front or back yards and may cross four to five lots until it reaches a catch basin. The catch basin is connected to underground pipes that discharge the water to the community pond for storage and cleaning.

After a rainstorm, the water in the pond will rise and if the elevation is high enough, the cleaner water at the top will drain from the pond through an outflow structure and eventually into a LWDD canal. The overland flow of stormwater over a LWDD canal bank and into the channel is not allowed. The untreated stormwater can impact water quality and dangerous washouts in the bank can occur.

The LWDD designs its canal banks and rights-of-way to prevent stormwater runoff from directly entering the canal system. A typical LWDD canal right-of-way is graded so the canal berm is higher than the surrounding land and stormwater will flow away from the canal. Due to the regular maintenance activities of the LWDD like mowing, as well as the natural settling of the soils, regrading of the right-of-way is one of the important flood control operations performed by the LWDD.diagram of LWDD typical canal right-of-way

Over time, property owners may also have to regrade their front, side and back yards to match their original drainage design. Settling of the soiarrow depicting how the flow of water can be slowed by vegetation and fencingls or enhancements such as landscaping materials or installation of fences may impede the overland drainage flow. This disruption can cause soggy areas in yards and standing water during heavy rain events. In severe cases, patios, garages and homes can be adversely affected. Property owners should be aware that it is their responsibility to ensure the overland drainage flow is maintained to the design condition.

Development activities that effect how much rain can soak into the ground, how much water leaves a property, and where it will go are regulated by the South Florida Water Management District. Community drainage system permits and plans may be obtained through this agency at www.sfwmd.gov. Additionally, permits for the crossing and use of the LWDD canal right-of-way for the installation of drainage infrastructure such as culverts and outlets can be obtained by visiting LWDD’s online permit system at www.lwdd.net/right-of-way/permitting.