Archive for category: O & M

Many factors must be considered by the water managers at Lake Worth Drainage District (LWDD) when managing a rain event. One factor not often thought of by the average person 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 all kinds of 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 a 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 a sandy soil is faster than into a clay soil because the texture of clay is much denser than the sandy soil. The infiltration rate of a 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 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 the flood control in southeastern Palm Beach County. For more information on water management visit our website at www.lwdd.net.

The Lake Worth Drainage District’s (LWDD) stormwater management system is made up of the canal channels, rights-of-way on each side of the canals, and controls structures and pumps. Consisting of a network of more than 500 miles of canals, over 1,000 miles of rights-of-way, and 20 major control structures, LWDD provides effective flood control and water supply for residents, businesses, and agriculture within its boundary.

Effective stormwater management is dependent on well-maintained canals and rights-of-way. But what defines ‘well-maintained’? A canal or right-of-way that some property owners may consider an eyesore is often considered well-maintained for flood control operations by water managers.

Some of the necessary components for effective flood control include the free flow of water in the canal channels to divert excess stormwater from properties, and unencumbered canal rights-of-way to provide access for regular maintenance and emergency response. Through the process of aquatic vegetation control, canal bank mowing, and encroachment removal, effective flood control maintenance is achieved.

There are numerous species of aquatic plants found within the LWDD’s canal system. Some aquatic vegetation has the potential to slow the flow of water within the canal channel or control structures. This vegetation growth is controlled with the application of herbicides and/or mechanical removal. Although not esthetically pleasing to some property owners, algae in canals is not a threat to flood control. Because algae are very small plants that break apart easily, they can pass through drainage pipes and control structures. This is good news since the herbicide used to treat algae can be harmful to the water body.

Canal rights-of-way and banks are mowed approximately 3 to 4 times a year. Flat-mowers mow the rights-of-way, and arm-mowers maintain the side slopes of the canals. High grass does not prevent access to canals or threaten flood control operations. It is not uncommon for grasses to grow several inches in height before mowing crews return to an area.

To enhance their property, residents adjacent to a canal sometimes place unauthorized vegetation or structures such as swing-sets, fences, and sheds on LWDD’s right-of-way. Encroachments must be removed because they may fall into the canal during high wind events causing blockages or slowing the progression of drainage. Additionally, encroachments can obscure sightlines for visual inspections, and impede LWDD’s access which is a critical component for public safety.

Flood control and the maintenance it requires comes at a cost. All property owners within LWDD’s boundary, whether adjacent to a canal or miles inland, are assessed at the same tax rate. In 2021 the assessed rate is $49.50 for a parcel equal to or less than an acre in size. By operating its stormwater management system to well-maintained flood control standards, LWDD can achieve its mission of effective flood control at a fair and affordable cost for all its residents.