A recent New York Times article about deferred maintenance on dams reminded me of the story of the Johnstown, PA flood in 1889.
Lake Conemaugh (originally called the South Fork Reservoir) was an abandoned reservoir retained by a 72-foot dam on the Conemaugh River about 14 miles upstream from Johnstown, Pennsylvania. The elevation drop between the dam and Johnstown was about 450 feet. The reservoir and surrounding land were purchased for recreational use by a group of wealthy sportsmen who failed to maintain the dam's spillways and discharge pipes. Following a heavy (4-6" in 24 hours) rainfall, the dam collapsed. The flood that virtually wiped out Johnstown was one of the worst man-made disasters in US history, killing 2,209 people.
The Wikipedia narrative describing the event and its consequences is worth reading.
The National Park Service manages a memorial exhibit about the flood near the dam breach, and helps maintain sections of walking trail along the Conemaugh River where the flood occurred. Johnstown has a museum about the flood.
The Pennsylvania Environmental Council's "Path of the Flood Trail" brochure includes a map of the area and some photos of the devastation.
The purpose of this lab is to model the Johnstown flood with digital elevation model (DEM) data using Arc's Spatial Analyst and 3D Analyst utilities.
Johnstown is located about 40.32N, -78.93W at the confluence of
the Conemaugh River from the east with and Stony Creek from the
Go to the USGS's National Map Viewer, search for Johnstown, PA, and set the viewer to frame a rectangle area that encompasses the town and the area eastward including South Fork. Click "Download Data," check the the "Elevation" box, and select "National Elevation Dataset (1/3 arc second) Pre-packaged ArcGrid format." Add this to your "cart" and "check out." The server will email you the zipped datafile. Once you unzip it, you can add it to your Arc map.
Note that this raster is in lat-long coordinates. You should resample it to PA State Plane South (NAD 1983 HARN meters) coordinates. (1/3-arc-second rasters are conventionally resampled to 30M cellsize.)
Go to the US Census Bureau's TIGER/Line shapefile distribution website and download the shapefiles for Cambria County, PA. You can extract the roads, rail features and streams as separate layers from the composite file if you like. These layers will help you get visually oriented.
Let's see what you can accomplish!
I used Spatial Analyst to create a simple narrative map with a few image-mapped links to pictures from the disaster. With a little creativity and effort you can do better.