The Bill Williams River Map...Planet Valley, 1953-2005

My perpetual map of the Bill Williams River, AZ is squeaking toward a state of preliminarity. The story of the BWR is a fascinating one. It is a large, sediment laden river with a fantastically skewed flood regime (i.e. flood peaks that are orders of magnitude larger than average flows) that has been bottled up by a dam with a tiny peak-release capacity since 1968. Thus, its potentially huge, but short-lived flood peaks (spikes of 50 to 150+k cfs) have been degraded to long-lived, low discharge events (bricks with prolonged peaks of no more than 7k cfs)  that have lots of time to impart change to the channel. Since the dam traps easily more than 95 percent of the river's load, lots of interesting things happen. 

The mapping that I have been working on is an attempt to document the morphological change in the river corridor over the last 60 years or so with a nice set of orthorectified aerial images from each decade. Lots of cool things can be done with the images, mapping, and GIS. So far, I have only mapped each generation and 'cookie-cut' them into each subsequent generation to illustrate the evolving mosaic of alluvial deposits. This is made quite simple with the analysis\overlay\erase and data\general\merge functions in ArcGIS. A much more elaborate scheme using the analysis\overlay\symmetrical difference tool is also in the works. Instead of the straight cookie-cutter approach, the sym difference approach essentially piles each layer on the other and then cookie-cuts it, creating a sort of virtual stratigraphy that documents what features have changed to what features (or have remained the same) over the time series. 
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In any case, the series of images above provides some visual insight into how a dynamic fluvial system evolves and creates the complex mosaic of deposits and surfaces that you see at any given time. In this case, the final map is the net result of only 5 decades of activity. Ahh...surficial geology...so simple, right? Soon the maps will have legends, etc. Just wanted to show some real progress. The image below shows how individual surfaces from each generation remain out there today in an intricate array.

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Google Earth and LiDAR overlay...Bill Williams River, AZ

Turns out it is pretty darn easy to overlay your spiffy LiDAR imagery
onto Google Earth imagery. Of course, some one had to walk me through
the few steps to take, but soon I will be proficient. Thanks, Heather!

This case is particularly cool because the LiDAR and the GE imagery
appear to show a similar point in time in an otherwise dynamically
changing river. The overlays include a hillshade and a slopeshade.
Both are made slightly transparent to let the 'natural' world shine
through. The mesh of the detailed topography and the details of the
gemorph clearly evident in the imagery is very cool.

These kmz files were created quite straightforwardly using
GlobalMapper. A very, very useful program.

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Mapping yet another tortured river...the Mighty Bill Williams River, AZ

It is tortured river season in my office. Lately, I have been tackling Nevada's mighty Walker River and its shrinking terminal lake (new term is terminus lake...but that is a bit soft); and Oregon's Owyhee River and its travails with lava and landslides; but now I am back on to the Mighty Bill Williams River of Arizona. You know, the Bill Williams River.

Included below is a snippet of the map I am working on. Shown are 6 generations of lines that document major changes in the channel, most since a dam was finished in the late 60s. One day soon, this map will actually make sense, I promise.

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The BWR is a special case. It is a roughly 35 mi stretch of river that traverses the hot desert below the confluence of two rivers that collectively drain more than 5000 square miles of western Arizona. Alamo Dam sits just below the confluence and traps essentially all of the sediment that would otherwise have gone down the BWR and to the Colorado River (well, at least to Lake Havasu). Also important to note is that the pre-dam BWR could attain peak discharges ranging up to 100,000 cfs, whereas the post-dam BWR can hardly exceed 7000 cfs owing to the outlet works of the dam. Thus, large runoff events that would have otherwise blasted through the system in a week or less (Spikes) are now converted to protracted, flat-topped hydrographs that lumber through the channel for up to several weeks to months (Bricks). Recall that these bricks are also sediment-free except for the sed picked up in the channel below the dam.

The result is an interesting experiment in channel change, sediment budgeting, and inadvertent (or otherwise) tamarisk farming. 

I won't be posting daily updates of this map, so don't worry. Be assured, however, that I will make a lot of noise when I finally finish it. This one is a long, long, long, time coming. Just ask the sponsors.

Some other BWR info: 

More LiDAR...different river

Another example of the of the standard hillshade vs. 'isotropic' hillshade (isoshade) concept previously described with reference to the Owyhee River, OR. These are from a couple of reaches of the the Bill Williams River, AZ. The BWR data set is fine until the trees get in the way. Both image variations are pleasing. The standard hillshade looks 'natural' but the isoshade image reveals more intricate details.

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