Hurricane Milton Operations Summary

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Soil Saturation and Drainage

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Many factors must be considered by water managers at Lake Worth Drainage District (LWDD) when managing a rain event. One factor is the varying water content in the soil which can have a significant impact on the drainage rate and flood control operations.

When dry soil is crushed in the hand, you can see how it is composed of many particles of different sizes. Most of these particles originate from the degradation of rocks; they are called mineral particles. Some originate from residues of plants or animals; these are called organic particles. The soil particles seem to touch each other, but a much closer look will show there are spaces in between the particles. These spaces are called pores. When the soil is “dry” the pores are mainly filled with air. After irrigation or rainfall, the pores are mainly filled with water.

When it rains, water is applied to the land, and it begins to seep into the soil. This process is called infiltration. The infiltration rate of soil is the velocity at which water on the surface can seep into it. The rate of infiltration is affected by the texture of the soil. For example, the infiltration of water into sandy soil is faster than into clay soil because the texture of clay is much denser than that of sandy soil. The infiltration rate of soil also depends on the existing soil moisture content. The water infiltrates faster when the soil is dry, rather than when it is wet. You can see this when it has been raining for an extended period. Puddling or pooling of water will occur.

If all soil pores are filled with water, the soil is said to be saturated and there is little to no air left between the soil particles. It is easy to determine if the soil is saturated. If a handful of saturated soil is squeezed, some muddy water will run between your fingers. The period of saturation of the topsoil usually does not last long. After the rain has stopped, part of the water present in the larger pores at the top will move downward. This process is called drainage or percolation. In coarse, textured sandy soils, drainage is completed within a period of a few hours. In fine-textured clay soils, drainage may take 2-3 days.

The type of soil and degree of saturation is a consideration when managing water. The flood control function is a balancing act. Water managers must provide adequate drainage for flood control while holding back water for

future supply needs. The LWDD has over 100 years of experience in managing flood control in southeastern Palm Beach County. For more information on water management visit our website at www.lwdd.net.

Avoid Driving on Flooded Streets

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Driving on flooded streets can pose significant risks to drivers. Keep this phrase in mind, ‘Turn around and don’t drown.’ While you may believe you can safely navigate through high water, the dangers far outweigh any potential convenience. Listed below are five compelling reasons why you should never drive on flooded roadways.

1. Unseen Hazards

· Floodwater can conceal various unseen hazards. Dangerous objects such as potholes, debris, and downed powerlines. Driving over or through this debris may cause considerable damage to your vehicle. The risk increases dramatically when drivers struggle to navigate unfamiliar terrain.

2. Vehicle Damage

· Water can wreak havoc on your car engine. Even inches of standing water can cause your engine to stall. Water can infiltrate critical components such as air intake, transmission, and electrical systems leading to costly repairs. Be proactive and park cars on higher ground. The cost of repairing a water-damaged vehicle can far exceed the inconvenience of temporarily relocating your vehicle.

3. Swept Away

· Fast-moving water can be extremely deceptive. Just six inches of rushing water can knock a person off their feet, while 12 inches can sweep away a small car. The power of floodwater is unpredictable, even a calm section of road can quickly become dangerous. It only takes a moment for a vehicle to be swept off the road, putting all occupants at grave risk.

4. Impaired Visibility

· Flooding can significantly reduce visibility due to murky water and rainfall. When combined with other hazards like malfunctioning traffic signals and washed-out roads, driving becomes even more perilous. What might appear to be a shallow ponding can conceal a canal or community lake making the end of the roadway and the beginning of the waterbody undiscernible. A driver may unknowingly steer their car into a potential drowning risk.

5. Public Safety

· Driving through flooded streets does not just endanger you, it puts others at risk as well. Drivers who attempt to navigate flooded roadways increase the chance of

creating hazardous conditions for emergency responders. By staying home and avoiding flooded streets, you will contribute to the quick recovery and safety of your community.

In the face of flooding, patience is crucial. It is always better to wait for the water to recede than to risk your safety and the safety of others. Heed warnings, stay informed, and prioritize your well-being over any immediate need to travel. Remember, when it comes to flooded roads, the best course of action is to ‘turn around, don’t drown.’ For more information on driving and flooded roadways visit the National Weather Service website at https://www.weather.gov/tsa/hydro_tadd#:~:text=What%20Is%20Turn%20Around%20Don,to%20water%20over%20the%20roads

That’s A Good Question

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Q. What is the ‘bleed down orifice’ in a discharge control structure?

A. In stormwater retention ponds/lakes, a discharge control structure is used to regulate the flow rate of stormwater leaving a site to meet state water quality requirements. The bleed down orifice is an opening in the structure which is set at a designed elevation. As the water rises in the retention pond/lake, it discharges through the bleed down orifice until the designed elevation is achieved.

 

 

Discharging Stormwater from Ponds

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In coordination with the South Florida Water Management District (SFWMD) 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 terms “Operable” and “Non-Operable” do not refer to the structures’ ability to provide flood protection but rather to their design and functionality.

Non-operable structures, also known as “passive structures,” typically feature an overflow weir or a triangular “bleed down” orifice installed at the stormwater pond’s designed water-control elevation. These overflow orifices facilitate the gravity flow of water through the structure into drainage canals, maintaining the pond water at the designed water-control elevation. Due to their passive nature, water will flow through these structures during rainfall, except in very dry conditions when pond levels fall below the water-control elevation.

Emergency Operable Structures incorporate the passive flow mechanism mentioned above, as well as a vertical slide gate with a manual operating mechanism (usually a handwheel) that allows for controlled water flow from the pond to drainage canals. This structure can be opened to manually lower pond levels after a rain event or in preparation for major weather systems, such as tropical storms or hurricanes to allow for additional storage capacity within the community’s stormwater ponds.

These structures, both operable and non-operable, are vital infrastructure for the neighborhood’s flood control. The responsibility of maintaining these structures belongs to the HOA and property manager. It is important to maintain these structures regularly during the dry season. Information pertaining to the maintenance and upkeep of the discharge control structures should be transferred to new board members and property managers.

The Emergency Operable Structure can only be operated with permission from LWDD. This permission may be granted at the request of an individual community or business, but more often, LWDD provides blanket permission to all communities and businesses based on forecasted weather conditions. In these cases, LWDD will notify registered representatives by email, specifying the times to open and close the Operable Structure. Communities and businesses can register designated representatives to receive these notifications at https://www.lwdd.net/authorization-contacts.

For more information about your stormwater management system visit  www.sfwmd.gov, to obtain a copy of your South Florida Water Management District permit.