This map from MLive shows roads closed due to flooding in Western Michigan. (Turn around, don't drown). Click through for the interactive version.
A similar map from NOAA shows flood gauge readings across the area.
The purple gauge in this above map is Grand Rapids at Comstock Park, which is showing flooding at almost 6 feet above flood stage.
The historical big flood in Grand Rapids is from 1904; this collection rephotographs scenes from that flood in 2004.
Hurricane Isaac brought with it high winds and a substantial amount of rain, and both of those combined has led to a lot of flooding. Here are some maps I've collected while the storm is still underway. You should know that for each of them I'll also give a link to the underlying mapping source so that you can get current information.
If you are in the affected area and need details about flooded roads or the risk of dams or levees bursting or anything else, do not trust this weblog for current information; seek out official and up to date sources.
Most of the maps are dated August 30, 2012, unless otherwise noted.
Rainfall
A good source for maps of observed precipitation is water.weather.gov, specifically the AHPS (Advanced Hydrometeorological Prediction Service). Here's a 7 day observed rainfall for Louisiana from that service, showing some areas with upwards of 20 inches of observed rainfall.
Predicted rainfall
A good source for rainfall predictions running out to the next 5 days (120 hours) is the Quantitative Precipitation Forecast (QPF). These models are updated several times a day and give rainfall estimates over the entire country. (Your rainfall will differ.) This is the run from Thursday, August 30, 2012, showing a predicted 5 day course for the remnants of Isaac to dump rain up the Mississippi and Ohio River valleys.
Predicted flooding
The National Weather Serivce Watch, Warning, Advisory Display shows this map with areas in pale green with warnings of potential floods, darker green (Arkansas) with current flood conditions, and parts of Louisiana and Mississippi with flash flood warnings. The accompanying text for some forecasts note that because of the dry and drought conditions the ground will be hard, and thus less able to absorb moisture leading to heavy runoff and flooding.
River gauges, current
Many rivers have flood gauges which measure and report current flood status. This is a map from water.weather.gov's River Observations page showing the whole nation, with flooding marked in color. You can zoom in to individual observations as well.
Here's a zoom of the New Orleans area for the same data. Please note that the gauges are only on rivers, and will not show flash flood areas, levee breaches, or other places where water is not usually found.
Satellite imagery
I'll be on the lookout for satellite photos that show flooding; those usually don't appear until after the storm has cleared, because any imagery sensitive to water will pick up the clouds first. Here's a NASA Aqua/MODIS image, pulled from their Rapid Response Imagery datasets.
The remnants of Tropical Storm Lee have made their way slowly from the Gulf of Mexico to the northeastern United States, bringing a storm with a slow-moving heavy rain. There is widespread flooding in the Susquehanna River basin and flash floods across the area. The Weather Underground's Jeff Masters has commentary on the storm from the morning of September 8, 2011, saying
An extreme rainfall event unprecedented in recorded history has hit the Binghamton, New York area, where 7.49" fell yesterday. This is the second year in a row Binghamton has recorded a 1-in-100 year rain event; their previous all-time record was set last September, when 4.68" fell on Sep 30 - Oct. 1, 2010. Records go back to 1890 in the city. The skies have now cleared in Binghamton, with this morning's rain bringing the city's total rainfall for the 40-hour event to 9.02". However, another large region of rain lies just to the south in Pennsylvania, and all of the rivers in the surrounding region are in major or record flood. The Susquehanna River at Binghamton is at 25', its highest level since records began in 1847, and is expected to overtop the flood walls protecting the city this afternoon. In Hershey, Pennsylvania, Swatara Creek is 18' over flood stage, and more than 8' above its record flood crest. Widespread flash flooding is occurring across the entire area, and over 10,000 people have been evacuated from their homes.
For current information, tune in to local news. Among the sources I have found that are broadcasting emergency flood coverage are WNEP TV-16 Scranton, the Times Leader in Wilkes-Barre, the Times Tribune, and WBNG-TV 12 Binghamton.
Emergency services channels can be tuned in via Radio Reference for Binghamton, Broome, Tioga, and Susquehanna Counties; Lycoming County Public Safety; Bradford County Fire; Schoharie County Public Safety; and other systems.
Here are some maps.
The Middle Atlantic River Forecast Center is a good first place to look for current information. This map from Wednesday, September 7, 2011 shows the flooding outlook for the area.
From the same source, point by point forecast river conditions:
This rain map, which Jeremy Denlinger pulled from the National Weather Service, shows a 72 hour rainfall total for the area.
Flooding in the Wilkes-Barre, PA area lead to mandatory evacuation of low-lying areas of the Wyoming Valley, according to a story in the Times-Leader which ran this map of affected areas:
Vermont was hard hit by Irene. There are lots of photos and videos out there showing some of the devastation and flooding; here are maps that give some sense for the area involved.
Vermont Flooding 2011 on Facebook is a good community resource, as is Mad River Valley Hurricane Irene. For volunteer coordination, see the VTResponse weblog.
Detailed city maps showing flooded areas are not yet available. FEMA maps show the most vulnerable areas, and are available for Burlington, Montpelier, Waitsfield, and other cities.
A collaborative map of the incident is VTIrene, hosted on Crowdmap. Another VTIrene collection by Dan Dowling on Scoop.IT has an aggregation of news, video, and twitter accounts.
Compare with the 1927 flood; the Landscape Change Program at the University of Vermont has aerial photography of that event. See the National Weather Service's Flood of 1927 information.
River information from the Northeast River Forecast Center (RFC).
Vermont road information from VTrans. Please check current road conditions; this is not a current road map. An interactive Google map of Vermont highway conditions has more precision.
Vermont New Road Closures is a crowd-sourced map, which includes information about local roads not otherwise noted on the official map. This is a snapshot from August 31, 2011.
Google.org's Vermont Flooding 2011 map has a series of map overlays; this one depicts bridges out, roads closed, and towns that are isolated. Much of the data can be downloaded in KML formats, and the interactive version of this lets you zoom in; this snapshot is observed August 31, 2011.
One day and seven day precipitation totals, from NERFC and AHPS.
The river is high. Will it flood? That's a very good question to ask in the morning before a storm; and the answer today turned out to be yes. Roads were inundated, Lake Barracuda emerged from its stormwater geyser, Depot Street filled with water, Mullholland Creek popped a manhole cover, and S. Main Street near Michigan Stadium filled. West Park's new water features get a workout.
Basements have taken on water, and the full extent of storm damage is unknown yet until we get the May 26 predicted rains.
Media coverage: Detroit News, noting that this is the 6th worst flood to date; AnnArbor.com, collecting more flood photos, including those of Lake Fingerle.
A few photos, with photo credits:
Lake Barracuda, captured at Depot Street by photographer Chris Dzombak. Photo used with permission, all rights reserved. The lake is named after Barracuda Networks, which occupies the new stilt-built stay-dry construction at 201 Depot St. More photos from Chris in the Flickr set Flooding at Depot/4th.
The river seen from above, taken by Kai Petainen, used with permission. His set Huron River Flood has photos and some short video taken from Island Park downstream to the Arboretum. Kai writes for Forbes with the weblog Sisu Investor.
Map of total rainfall storm to date for this storm, from the Weather Underground, as of 1:05 a.m. Thursday. Pick "total precipitation" from the radar screen, or pop out the "1 hr precipitation" from the side in the Weather Underground Classic user interface and animate to watch storms come in.
If you're looking for data, you'll find the specific current and recent historical information from these sources.
The USGS Water Data Discovery page describes the National Water Information System which has reat time, predictive, and historical data for use.
USGS National Water Information System real-time water data for gauges in the area is measured every 15 minutes and reported with 60-90 minutes delay. Look at the gauges for the Huron River at Ann Arbor, and you'll see a graph showing current levels. It's also possible to go back and get the data as data going back as far as 120 days, and to retrieve prior years data on a daily basis.
There is also a gauge on Allen Creek which has collected data from some storms, but which is not in the National Water Information System and not always online. Allen Creek empties into the Huron River just downstream of Argo Dam, and at peak flow it can dump at least 1500 cubic feet per second into the river. I have seen data from one storm, and it looks like this can turn into 600 cubic feet per second at the next gauge, though that's only one data point.
You can look yourself at the tabular data for the river rating of the Huron River at Wall Street, which shows a level by level matching of flow vs water height. If the river is very low (300 cfs), then a sudden burst of 600 cfs will raise the level of the river by about a foot, and a burst of 1500 cfs will raise the level of the river by about two feet.
River forecasts come out routinely between 9:00 a.m. and 11:00 a.m. and if needed a second forecast goes out between 9:00 p.m. and 11:00 p.m., according to National Weather Service meteorologist Danny Costello.
For more media information about products provided by the NWS, here's a slide deck I found on the Grand Rapids NOAA site as a media briefing. It explains in one of the slides a key aspect of predictions: the weather service changes from "watch" to "warning" when a forecast probability goes up to 80% likelihood of the event occurring.
