Hurricanes and tropical weather systems have potentially enormous impacts on lakes, ponds and stormwater devices. Since managing these water bodies has been our business for 40 years, we wanted to give you some guidance that can help you make the most of a bad situation. In addition to this guidance, we wanted to explain our position on lowering water levels in lakes and ponds in preparing for a storm and the possible resulting flooding. We will list possible tasks to consider before, during and after a storm.
Unfortunately, our ability to predict the path, speed and intensity of tropical systems is not exact. We may have several days to anticipate and prepare, but often only hours, or less, are available before we know specific details about:
- Wind speed
- Wind direction
- Rainfall expected
- Duration of rainfall
- Runoff intensity and duration
- Power outages
- Transportation interruptions
- Erosion potential
- Dam or embankment failure potential
Therefore, some things can be done to improve general conditions in advance regardless of if/when a storm hits:
- Keep drains, inlets and outlets clean and open
- Keep spillways, embankments and dams well maintained to limit erosion
- Install trash racks or debris guards on drain risers and standpipes
- Keep aquatic vegetation maintained and control floating weeds/filamentous algae
- Keep the watershed reasonably clean of trash, yard waste, sticks and debris
- Secure loose items that may be blown or wash into the water body
Preparing for the storm when forecast:
- Turn off and secure fish feeders, feed barrels, fountains, diffused aeration systems, pumps and any electric devices
- Secure boats, fishing equipment, potted plants and any loose equipment
- Try to minimize entry of any grass clippings, leaves, brush, other vegetation, or sediment into the pond
- Depending upon your situation and willingness to encounter the obstacles listed below, consider lowering your water level (see article following this guidance)
During the storm:
- Be safe and stay inside if you haven’t evacuated
- Stay away from inlets, drains, and spillways while water is flowing since the current can be extremely dangerous
- Observe the water level if possible and practical frequently to detect significant erosion or overtopping of the dam
- Avoid downed power lines and other sources of electricity
- Monitor forecasts, road conditions and communicate with your neighbors if practical
After the storm:
- If practical clean off as much trash, debris, leaves, pine straw and other organic matter off the surface of the pond
- Anticipate declining dissolved oxygen in the water as a result of decaying organic matter
- Get fountains and aeration systems working as soon as possible
- Do not feed the fish for at least several days
- Circulating water with pumps, outboard motors or spraying water can provide critical dissolved oxygen
- Divert runoff full of sediment, nutrients, pesticides, debris or organic matter if possible
- Protect yourself from mosquitoes and other harmful insects or animals
- Keep drains, outlets and spillways clean so excess water can drain
- Repair any structures or equipment that may have been damaged
Our Position on Opening Lake Drain Valves for Flood Control
Some local and state agencies recommend lowering the water level for several days before an expected storm. However, they are usually dealing with large publicly owned lakes with sophisticated drain and valve systems. We usually advise against opening drain valves on private lakes, ponds and stormwater devices. In our experience over 40 years of lake management, we have learned that opening the valve for flood control is quite often a bad idea.
- Lakes and ponds we manage were not designed or intended to have the valve opened for flood control. If flooding around the lake is a problem, either the primary drain needs to be larger, or an emergency spillway needs to be added (or enlarged).
- The valve is usually the most fragile component of any lake. Damage repair can be very expensive and probably requires complete lake draining.
- If a stick or piece of debris gets lodged in the valve while it is open, it may not close. The lake could drain completely.
- An open drain valve can be very dangerous. If a person or animal gets sucked into or on an open drain, death is possible.
- The lake may take an extended time to refill. The drained lake will not be attractive. Weeds may cover the bare side slopes of the partially drained lake.
- We may not be able to drain the lake sufficiently to have enough flood water storage by the time the flood water arrives. Most lakes we manage must have at least 3 to 5 days with the valve open to lower the lake enough to help. We rarely have a reliable forecast that far in advance.
- Rainfall predictions are not accurate enough and too variable from location to location. If heavy rain is predicted and doesn’t occur the lake water level may remain low (and ugly) a long time.
- Water drained through a lake valve is usually deep water late in the summer (hurricane season). It has a bad odor that offends property owners below the dam.
- Downstream property owners perceive the open valve makes their flooding worse.
- Manipulating the drain valve for lake water level control requires considerable time. We are very busy investigating possible damage to dams and drains after any flood event. We must take the time and interrupt that very important service to close a valve before the lake water drops too low. Many drain valves are only assessable by boat. If another storm is forecast, we may have to start all over. Valves must often be unlocked, and we have to have a key. Many valve stems require special wheels or handles to be opened.
For these reasons, we have adopted a general policy of discouraging the practice of opening a lake valve for storm related flood control. In fact, if a client insists, we require a client signature on this agreement that identifies our reasons for discouraging the procedure, limits our responsibility or liability for damage and explains why our significantly higher fee for the activity is justified. Please sign below.