Disasterous Flood Problems In Pennsylvania
UPDATE: The river at Milton crested lower than predicted, but even at that level, some homes would have been underwater. Here is some video that our folks took over at Lock Haven this morning.
ORIGINAL POST: Even though the rain has ended and creeks are receding, there are a couple trouble spots on a major river that could cause homes to go under water in Pennsylvania. According to NOAA AHPS, two river locations will be above Major Flood Stage (which is worse than Flood Stage and Moderate Flood Stage) in the next 48 hours, shown as purple below (two creeks are also shown, but they are already receding). The worst case, according to NOAA predictions, would seem to be the West Branch Susquehanna River at Milton.
The forecast prediction (green line below) is for the river to crest over major flood stage around noon tomorrow: 26.3 feet. At 25 feet, the page notes that "Numerous homes in Milton and West Milton will flood. High water affects the American Foods Plant in Milton. Homes on South Water Street in Milton are flooded." Sadly, this would be the 10th time in history that the river has been that high, though in recent memory only 1996 and 2004.
Another local river, the West Branch Susquehanna River at Lock Haven, Pennsylvania is forecast to crest at 27 feet tonight, 17 feet above normal and 2 feet above Major Flood Stage. This would put the gauge height at #6 highest, or #2 highest since Hurricane Agnes in 1972. While this sounds terrible, (a levee was built after the '72 flood and has been tested in high waters twice since -- so tonight shouldn't be a problem.
NOTE: All charts on this page have been archived; click on each for the live, updated version.
The whole river flooding forecasting thing is kind of fascinating -- and dangerous to local residents -- because of changing geography, especially in city areas where runoffs change frequently, and interactions amongst tributaries, rivers can do strange and unexpected things.
And one river doesn't behave like another. For example, our local paper says there was flooding in Unionville and Milesburg today. I wanted to get some pictures, but there is no river gauge near Unionville, so I couldn't "gauge" what was happening out there. And I've only seen major flooding in Milesburg once, and today's gauge reading was nowhere near that. And the other local gauges' "streamflows" -- the amount of water flowing through the creeks -- at Milesburg and Spruce Creek, were much closer to the floods of 2004 than 1996 than the Milesburg gauge I normally use. So I assumed there was no flooding there, while in reality the local paper points out that a tributary flooded, where there was no gauge, before it dumped into the creek.
If you have an accurate representation of the local geography, or at least elevation, you can make a pretty good prediction of where water will flow at certain river gauge heights. The trick is the timing, and that's the part that we're not that good at forecasting yet, because it depends on how much rain falls over what time period, which can vary greatly over a short distance. If the rain was uniform across a large area, it would be easier, but it's usually not, especially with summer thunderstorms.
NEAT TIP: You can sign up for an email service that will email you or your phone when your local river gauge goes over a certain height. Select your site from the USGS site and click on "Water Alert."
