02-26-2005, 06:47 PM
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Flooding problems could be pending
[url "http://www.spinalcolumnonline.com/1editorialtablebody.lasso?-token.searchtype=authorroutine&-token.lpsearchstring=Kevin%20Elliott&-nothing"]Kevin Elliott[/url]
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Last May's rainstorms drenched the lakes area in a manner that hasn't been seen in nearly 100 years. In fact, that's exactly how the storm was classified — a 100-year storm, or one that only occurs every 100 years, with 5.5 inches of rain falling during the peak of the storm on May 22 and 23. According to County officials, approximately 220 homes experienced sewer system backups and flooding in their homes due to the rains, including some in Milford, Oakland Township, Rochester Hills and Royal Oak. Waterford Township was the hardest hit within the county, with a total of 102 homes that experienced flooding.
The total precipitation in White Lake was 37.04 inches in 2004, compared to 35.7 inches in 2002. However, much of the moisture came in excessive rains, rather than spread out through the year, according to Bill Deedler, a climatologist for the National Weather Service in White Lake.
According to the National Weather Service, 2004 was a roller coaster of temperature and precipitation fluctuations. While the beginning of Jan. 2004 was deceivingly warm, the end of the month became very cold and stormy. The weather held and led to the seventh warmest spring with extremely dry conditions in April with only .69 inches of precipitation. But excessive rain in May resulted in all Metro Detroit stations reporting over 8 inches of rainfall.
As a result of the flooding, Waterford Township Supervisor Carl Solden declared a state of emergency on May 25, 2004.
Oakland County Drain Commissioners John McCulloch has said in the past that part of the reason for the flooding was that many of the drains in the township, which were built as agricultural farming drains, have become obsolete. Therefore, the drains are not equipped to handle the influx of water which they received last May.
However, the biggest factor in where rainfall and snowmelt will go this year may ultimately be up to mother nature. That's because one of the biggest factors of flooding conditions may depend on the amount of water present in the ground and how high the water table is.
Ground water is simply water that is in the ground that comes from rain, snow, sleet and hail, which soaks, or percolates, into the ground. The water moves into the ground, passing between particles of soil, sand, gravel and rock until it reaches the point where the ground is filled, or saturated. That point is called the water table.
Another way to picture ground water and the water table is to think of digging a hole on a beach. Once a hole is deep enough, water is eventually found. That water is ground water and the point at which it is reached is considered the water table. When the ground water reaches a point above land, such as areas of low elevation, it is then considered surface water.
According to Dr. Lawrence D. Lemke, at Wayne State University's Geology Department, a flooding event typically occurs when the water table reaches the surface of the earth.
"When we have a flooding event, it can take many days, and in some cases, weeks, for the water to subside," Lemke said. "After the water table rises to its highest point over a period of time, new water input is cutoff and we don't have more melt water percolating into the ground. Then the water that is already there will tend to flow very slowly away from any high areas toward low areas and re-equilibrate. It can take anywhere from weeks or months in some cases."
When the ground becomes saturated, the water typically flows to local rivers and lakes. However, flooding problems may be more likely when the ground becomes so saturated that there is little room for more water to be added, thus raising the water table. In addition, excess water can also affect lake levels, which may be problematic to lakefront property owners.
To help alleviate excess water, the Oakland County Drain Commissioner's Office often draws down lake levels below their legal levels in the fall to create a cushion for spring rains and snowmelts. However, according to drain officials, lake levels are already rising above their legal levels.
"It's under control now; it's not a problem. It's just that we don't have that customary cushion throughout the lake and river systems that we would have liked to have had, had we had the opportunity to generate that in the fall," Oakland County Lake Technician John Benedict said. "We had rains, and the groundwater table was already high at that time. We just can't get it down very rapidly."
While Benedict said there is no problems with excess water at the moment, he said heavy rains similar to last May could easily result in flooding.
"If the rest of the winter turns relatively dry and good and cold, we could probably generate some kind of safety margin in these lakes, but right now we are doing everything we can draining off water, and we just don't get very far."
In order for draw downs to be conducted, a lake must either have a legal level established by the courts or Michigan Department of Environmental Quality (DEQ) approval.
Legal inland lake levels are established after two-thirds of the lakefront property owners sign a petition to establish the levels and submit it to the County Board of Commissioners. The board then initiates the action to determine the normal level of the lake, which is usually done through a study by a licensed professional engineer. The levels is then set by the Circuit Court in accordance with the DEQ. Lakes may have both winter and summer levels established.
Lakes with legal lake levels typically use a lake control structure to maintain the lake levels. A control structure is an artificial barrier used to regulate the level and may be in the form of a dam, a weir, pipe or any other type of barrier. Lake levels may also be controlled by using an augmentation well or pump to put additional water into a lake, or reduce water levels.
According to Steve Korth, assistant chief engineer for the county drain office, lakes with legal levels are usually drawn down by about 6 inches in early November and brought back up around April 15.
"We use our draw downs more for a protection measure against the ice damage and for the extra cushion for heavy spring rains," Korth said. "We found that to be very useful in regulating the chain of lakes that we have, and for protecting against flooding and things of that nature."
Although draw downs can be a useful a tool in providing a buffer for spring rains and snowmelt, unexpected weather during the late fall or early winter can sometimes negate lake level draw downs, which may have been the situation last fall.
"This year we began our draw downs toward the end of October and the beginning of November, then we had our late November and December rains," Korth said. "Looking at the charts, it reversed a lot of the water we lost. If you look at the levels now, many of the lakes appear to be higher than the winter (legal) level. It's just the nature of the weather we received."
While each lake fluctuates every week, the majority of Oakland County's lakes are already over the legal level for the winter, according to the drain department's weekly legal lake level measurements.
Union Lake, in Commerce and West Bloomfield Township, rose from .28 inches above the legal level on Feb. 4, to .33 inches on Feb. 11. However Long Lake, in Commerce Township, went from .75 inches above the legal level on Feb. 4 to .35 inches below the legal level on Feb. 11.
"All the dams are being used," Benedict said. "Some of the structures, one at Long Lake in Commerce, has an 18-inch pipe, and that's been open and running for months. The amount of water that is discharging is highly unusual, even during the winter when there is a normal amount of water. That's a good indicator that there is a lot of groundwater just feeding into that Long Lake-Cooley Lake area.
"There are a host of indicators that I'm familiar with, that all seem to have the same message attached to them: that we could be in trouble come spring. Then again, it could be dry and we could have normal rains, and I think we would be able to handle it at that time."
Other indicators of a high water table may be soggy ground or standing puddles that appear for longer than normal. Water seeping into basements may also be an indicator that the ground around a home is saturated.
"It's pretty much the same in all the areas that we are responsible for, the 55 lakes that we directly or indirectly control," Benedict said. "In one manner or another, they all show that same kind of high water and large volume of discharge that is continually flowing, and it just goes and goes and doesn't really taper off at all.
"The snow pack isn't feeding it. These rains that we are getting aren't feeding it. No matter what the weather conditions are, it just continues. That's why I conclude that there must be a very high water table."
While there is a good chance for flooding, he said the problem is that there are only limited actions that the department can take to limit the effects of excess groundwater.
"It's like trying to bring a freight train or a battleship to a stop," Benedict said. "One you turn the brakes on, it's a long way until it stops."
One way to alleviate flooding is by opening dams and weirs to allow for more water to leave an area before it reaches its maximum load. However, a problem arises when one structure is not able to keep up with the amount of water it's receiving from another.
Benedict used the Van Norman control structure as an example, which has a extremely large capacity to release water. Benedict said that if the dam were to be open to 100 percent capacity, it would flood out all of the area directly downstream, which would be Woodhall Lake.
"Consequently, you have greater and lesser abilities to handle the waters," he said. "When you do that, you are backing it up. Last year it got very tense, where we had to hold back water purposely or else flood everybody else downstream... once you discharge from the top of the upper end of the Clinton River, around Clarkston, you dump everything into it and let it run on down... then you get to the flatter part of Waterford and everything seems to spill out over the banks."
Whether or not the lakes area will see substantial flooding this year will also be largely dependent upon the weather.
Deedler said a long-term precipitation forecast for the year is not yet available, however, he expects the recent conditions to prevail this year.
"The wetter trend continues," Deedler said. "We've been in the storm track for the last couple years, particularly last winter and this winter, in this area. Looking at 2002-03, that really started it. I've noticed around here, the lower and swampy areas are all water now.
"I looked into early spring and we tended to keep in the storm track like we are. I would say precipitation, when I went with the normal to above, and I think with the fluctuating temperatures, which were really pretty extraordinary through the winter and into the spring, our chances of snow into March and April are still pretty good. Then, we are right back in the 60's or 70's. I don't see much change in the overall pattern into early spring, other than we will finally finish up on the snow, which is always the case."
But while the weather and water table may be problematic for floods this spring, excess water will likely be good news for those concerned with adequate lake levels this summer.
"I've seen so many summers when it has been dry and very difficult to enjoy the lakes that (residents) pay so much to live on, when I see the prospects for a normal water level and people being able to boat and fish and recreate on the lakes, it's a nice return for their investment," Benedict said.
The relationship between lake levels and water tables are a typically directly correlated, as explained by Lemke.
The uppermost aquifer in any system is considered an unconfined aquifer, meaning the water table is free to move up and down if we have more or less water, he said. In some places that water table is controlled by the presence of surface water, like a lake or river. If you are close to one of those, if the lake level goes up, then typically the water table will go up along with it.
"There is always an interaction between surface water and ground water," Lemke said. "Typically, in very wet seasons like we are in right now, when the rivers are running high, water tends to flow out of the rivers and into the groundwater system and recharge it. In the summer months, the system can work the other way, groundwater can discharge into the rivers and feed them and keep them running."
According to Deedler, White Lake has already received over 51.8 inches of snow this winter, while the normal for the year is between 55 and 60 inches. With about two months of possible snow left, Deedler said he expects a total snowfall that could reach as high as 70 inches this year
"We've got the low 60's and we've got a good month and a half," he said. "March is a pretty volatile month for storms and weather, the addition of either snow or rain is only going to help the lakes."
Kevin Elliott is a staff writer for the Spinal Column Newsweekly
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