It’s the middle of summer with hard – dry baked ground surface flash floods and runoff are a likely threat to commercial and public properties. How do you best control and protect your property from heavy rains? In more susceptible flood areas of your property, creating retention and detention ponds can be very effective. These depressions in your property are designed to help minimize the effects and possible damage by heavy rainfall, snow melt and sudden downpours that cause flooding. They help capture runoff that could otherwise damage your well-maintained landscape.

The Definitions

Retention ponds are wet ponds. Typical characteristics include water in the depressed area and steep side banks. Detention ponds are traditionally dry except during flooding weather to help control and manage the movement and settling of water. In some instances, detention ponds are used as a park during dry weather.

Maintenance

Both areas require much of the same maintenance to assure they properly function as they were designed. Both ponds need to be mowed regularly – keeping grass to a height of four to six inches to ensure healthy growth and minimize weeds. Dumping of grass clippings and other items should be discouraged. Herbicides should be used sparingly or not at all, as they could be washed downstream and create toxic conditions. Special care needs to be given to pipes or channels leading in or out of the ponds. Removal of trash and debris are crucial steps to make sure the proper drainage flow is maintained. Plugged channels can create erosion in other areas of the pond causing the integrity of the structure to fail, resulting in greater damage.

Detention ponds often have sediment that settles at the bottom of a pond that needs to be removed once the pond has dried.

Retention ponds tend to need more monitoring because of their purpose – holding water. Slopes of retention ponds need to be checked for erosion at least once per year, and more frequently if the season has been unusually wet. In retention ponds, floating litter, algae and shoreline erosion are common, as well as stagnant water producing odors and breeding grounds for mosquitoes. Sediment build up needs to be documented as the removal process is much more difficult. These conditions require ongoing monitoring and maintenance plans.

Checklist

We compiled a quick checklist to monitor and properly maintain retention and detention ponds and we can offer this service as part of our base maintenance contract if needed:

• Routine inspections to evaluate damage to slopes, channels, and outfall structures performed annually and after major precipitation – heavy rainfall, flooding, and snow melt.
• Vegetation management to maintain native plant growth at a healthy height (four to six inches) and limited or no use of herbicides.
• Trash, litter and debris removal – paying particular attention to inflow and outflow points and devices.
• Check equipment of all mechanical devices including fence gates, pumps or valves.

Retention and detention structures were built for the purpose to protect from flooding and to aid in the capture of water runoff from heavy rain or snow falls. When maintained properly, retention and detention ponds minimize the effects and help maintain a protected and beautiful landscape.