Spring 2010 Flood Discussion
 

This thread is for the discussion of lakes region flood potential throughout spring 2010.

The lake is currently above-full, and there is more snow in the surrounding hills to melt. There are also signs that another heavy rain storm is on its way for early next week. The lake continues to rise.

Further adding to the problem is all of the rain and flooding we had/have in Mass (10 inches in one day). The Merrimack is more than full so I'm sure that will restrict how much can be released from the lake

As SteveO points out the Rivers are indeed full. Which does represent a problem. However I looked around this morning at watershed data, and what I see is that As they operate dams reactions are corresponding. Which means they aren't behind. Right now it doesn't appear that there is more water coming into the water sheds of NH then they can disposition. This is good.

Now As far as the snow in the mountains is concerned I see to things here, one the rate at which it melts and the current conditions of the water table. If the water table is where is should be then the melt of will make it to the streams and into the lakes. However if the water table is low, the melt will have a chance to soak in and not as much of it will make it to the lakes and streams.

This also holds true when we think of rain. The problem down here in Ma. Hasn't been the Volume of rain, it is how quickly we have been receiving it. I have watched and for the most part things are drying up very quickly. Main tributaries like the Merrimac are the last to recover. Hence more rain could mean problems if it comes quick and heavy... however as long as it doesn't down poor for 4 days we are probably ok.....

Next weeks rain (early week) could be troublesome, but it looks to be drier after that.

Flood Watch
 

Flood watch has been issued for all of New England except for the northern 2/3 of Vermont, northern Maine, and outer Cape Cod. Flood warnings remain in effect for parts of eastern Massachusetts for rivers that are still above flood stage from the last storm.

Heavy rain now appears likely from tonight through Wednesday night. A period of strong winds is also likely in that time frame, as yet another east coast storm stalls nearby.

This time around, it does not appear likely that the mountains will get snow. Snowmelt from there will add to river levels. Snowmelt will continue even after the rain stops, as summerlike weather is expected at the end of the week. Therefore, rivers will stay near or above flood stage for at least a week, perhaps longer.

Trees that have been weakened by previous strong winds are now more likely to fall. Trees whose roots have been loosened by recent heavy rains may also fall this week, even in light winds.

The lake continues slightly above full level and is likely to rise for the foreseeable future. Wind-driven waves are already eating away at the shoreline and are bringing debris into the water. Winds at Black Cat Island reached 39 mph from the southeast today. Waves were averaging about 1 foot with a few waves at 1.5 feet.

With that said, boating on this lake will be extremely hazardous until the lake level recedes and debris has been cleaned up. The normal amount of iceout debris has been compounded by flood debris this year, and flooding continues to add debris to the water. Some have observed entire sections of dock floating in the waves, and this will continue to happen.

Debris may not be easily visible. Boating at greater than headway speed is not advised until the flood situation is over. Even in calm water, a board can lie flat and its color can nearly match the color of the water, making it nearly invisible until it punctures the hull of your boat or damages your propeller.

Rescue at this time of year will not be quick, because many would-be rescue boats are not yet ready for this year's unexpectedly early boating season. Furthermore, water temperatures are very cold. Even if temperatures reach 80 later this week, you will not last long in the 40-degree lake water if a sudden mishap puts you there.

The mountains did recieve some snow as of this morning but it will turn to rain soon. Cannon had 3 inches this morning and the mountains of western Maine had recieved 5-6. That should end up downstream in a few hours I'm afraid.

The lake has risen a bit more overnight, and is now about 7 inches above full. This is 6 inches below the flood level of April 2007, and 12 inches below the 1984 flood level.

More rise is likely. Rapid rise is unlikely. Prior to this most recent rain event, there was about 2 feet of snow in the Ossipees, reported by hikers. They said it was a frozen solid snow, most likely the result of having absorbed a lot of rain and re-freezing. This, and the snow in the White Mountains, will be melting rapidly over the next few days as temperatures rise to near or above 80 on Friday and Saturday.

This will keep a steady flow of water entering the state's rivers and lakes. The rivers are likely to remain at their current levels through the weekend, or else recede very slowly. Lakes will likely rise.

I was looking at the Mount Washington web cams and there is not much of a snow pack. This should be helpful in not contributing to heavy run off into the Lake and rising the flood waters to a more dangerous level.

I am really looking forward to nice summer weather. Hopefully the worst of the heavy rains has already taken place.

With the current discharge rate of 2300cfs, how long does it take for the lake to drop an inch based on no rain? Just curious.

I have a friend in Parker that wants to launch and can get out at just above full lake, but not by much.

Looking at the DES website today, it appears that the lake has come down about .14 feet from last weekend and that is roughly about 1.6 inches... now that isn't with the dam entirely at 2300 cfs... however that should give you some ideas..... I would say we are a good 2 or 3 weeks from getting down to the full lake mark... and that is assuming no appreciable rain.....

And keep in mind that although there hasn't been much rain the past few days, water is still flowing pretty quick all over. The lake is still filling up with runoff and snowmelt.

Don't forget that tree areas have a much cooler climate than open areas. There is plenty of snow in the woods at the higher elevations.

When you hike in the higher mountains, you find forests that are much cooler than open slopes at the same elevation (you can feel the sudden temperature difference as you pass from one to the other.)

The areas shaded by dense evergreens hide deep snow from easy view, and the snow there lasts well into the warm weather if there has been a lot during the winter. This past winter brought enormous snowfall dumps to NH elevations above 1500 feet. So even while the exposed slopes may be melting off quickly, the shaded areas will continue to produce snow melt through the spring.

The amount of contribution will gradually dwindle as the rapid-melt sources go bare and only the shaded slow-melt sources remain.