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:
- Flood protection and drainage systems
- Quality of existing underground water supply sources
- 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.
The 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.
April is Water Conservation Month
/in Drought, News, Water ConservationPalm Beach County Commission passed the Mandatory Year-Round Landscape Irrigation Conservation Ordinance. The provisions of this Ordinance apply to all users providing landscape irrigation from all water resources within the boundaries of unincorporated Palm Beach County with the following exceptions:
Link to: PBC ‘s Year-Round Irrigation Ordinance
How Flood Control Works
/in Flood Control, News, ResidentialMan-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:
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.
Potential Impacts of Sea Level Rise on Water Management
/in Flood Control, NewsExcerpt 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:
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.
The 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.
Annual Report to Landowners
/in News, ResidentialExecutive Director Tommy Strowd, PE, presented his annual report at the Landowners’ meeting on Jan 5th. Mr. Strowd reported on LWDD’s accomplishments and operations during 2021 and future goals for the new year. If you were unable to attend the meeting you can watch a recorded version at the link below.
Water Flows Downhill: But Not Always In the Desired Direction
/in Flood Control, News, Residential, Water QualityStormwater 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.
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.
Over time, property owners may also have to regrade their front, side and back yards to match their original drainage design. Settling of the soi
ls 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.