A recent Virginia Supreme Court case highlights a deceptively dangerous obstacle on many of Virginia’s waterways: the low head dam. A low head dam is simply a dam that goes all the way across a river and is designed so water flows over the top of the dam, rather than around it or through a hole in the dam. Generally low head dams are not very high, often just a few feet, and are designed to create a pool of water behind the dam for irrigation or to create a flow for a waterwheel. Many of these dams were constructed a century or more ago but are still in existence today.
These dams look quite innocent. Usually upstream there is a placid pool of water and over the dam flows a lovely stream of water creating some attractive boiling action near the downstream side of the dam. However, this harmless appearance is quite deceptive. Low head dams are so dangerous that they are often called drowning machines. Many of these dams have a drop or waterfall of less than 10 feet, so they don’t seem large enough to be dangerous.
The reason for the danger is the circular motion of the water near the dam. When the water flow is strong, it flows over the dam with force. The water crosses over the top of the dam and then falls to the bottom on the downstream side where it strikes the bottom and is deflected back up towards the dam. As the water nears the surface it curls back away from the dam face in a circular motion as it encounters the flow over the dam and is pulled to the bottom again. This forms a continuous circle of water, called a hydraulic, from which even the strongest swimmers often cannot escape. They are circulated up and down until they drown. One of the things that makes the hydraulic even more dangerous is that the water flowing over the dam and entering the hydraulic becomes aerated or filled with air. Surprisingly, aerated water is actually less buoyant and thus harder to float or swim in.
The danger associated with the hydraulic below a low head dam is often increased by the time of year. Hydraulics are usually stronger when the flow of water is heavier; this most often occurs in the spring. At that time of year, the water is colder than in the summer or fall. With the lower temperature, Hypothermia quickly saps the strength of even the strongest swimmer in these circumstances.
A recent Virginia Supreme Court case, Volpe contra la ciudad de Lexington, 2011 Va. Lexis 80 (April 21, 2011) cited such a tragic incident. The plaintiff was a young man and he decided to go swimming in a park in the City of Lexington on the Maury River. He had often gone swimming there and swimming was one of the recreational aspects for which the park was intended. However, about 85 feet down river from the place where swimmers were to enter the water, and where this young man entered the water, was a low head dam. There were apparently no signs warning of the dangers of a low head dam. The young man had often swum there and had even played on the dam and jumped over it when water levels were low. On this day, however, water levels were high. Unfortunately one of the deceptive problems of low head dams is that the water above the dam can appear relatively calm and placid even with a very high flow. The young man was swept over the dam into a hydraulic and drowned.
The parents filed suit alleging that the City of Lexington had a duty to warn of the dangers or otherwise make the low head dam less dangerous, and that the City was negligent for not doing so. Under Virginia law, however, a city is immune from being held responsible for most acts of negligence. In order for the city to be liable, a plaintiff normally must prove not just simple or ordinary negligence by the city, but the much higher standard of gross negligence. At the conclusion of the trial, the jury couldn’t reach a decision, so the trial court finally took the issue away from the jury and decided against the plaintiff’s estate. The Virginia Supreme Court decided that the trial court erred, reversed the trial court’s decision, and sent the case back for a new trial with a new jury.
The tragic lesson of the case remains: Be careful of low head dams. There are many such dams in Virginia. Bosher’s Dam, with which those of us who live in Richmond are well familiar, is such a low head dam and many people have drowned there despite numerous warning signs posted near the dam. Further along the James River, just in the Richmond area, are several more low head dams or structures causing hydraulics: Williams Dam, including the “Z” Dam; Grant’s Dam; the pipeline shelves, and Belle Isle Dams.
Before boating or swimming in an unfamiliar waterway, check with the locals or review charts to determine if there are any low head dams on the route and, if encountered, portage around them or stay well clear of them. One of the dangers of low head dams is that from the upstream side they can appear only as a flat line on the horizon and thus are not easily spotted from upstream. Look also for the concrete abutments on the side of the river that most low head dams have.
Generally stay away from low head dams if swimming or boating, especially in high water conditions. As discussed above, many people have drowned in the hydraulics on the downstream side of such dams and they are deceivingly dangerous.
Sobre el Autor: Chris Meyer es un car accident lawyer in Mechanicsville Virginia with Allen & Allen. Mr. Meyer helps car accident victims in Mechanicsville, Hanover and Ashland recover damages from their injuries. He has developed a reputation on the Virginia Rules of Professional Conduct and annually lectures on Virginia Legal Ethics. He also lectures regularly on recent decisions of the Virginia Supreme court.