State of the Clark County map, March 25, 2010

This one is huge, huge. This map is the focus of the Nevada Digital Dirt Mapping Project. It has a team of as many as 10 (now) at any given time. Two of us are 'master' mappers, the others are learning fast and occupying lower levels. We are seeking another 'master', trust me.

The county map below provides some context for the density of linework...much of it compiled from published sources. However, most of those sources are quite general and particularly weak on the Q geology...which is our focus. Note, a couple of them are strong on Q, which is good news for us.

The second image shows a close-up in the NW corner of the county. The mismatch you see is dominated by our refinement of the bedrock-alluvium contact. Other mismatch related to incomplete (in progress) carving out surficial units. In other words, the polys are based on the original linework...haven't rebuilt the entire set yet.

(download)

State of the Owyhee River map, March 25, 2010

Believe it or not, this one is almost done. I have posted proof of that before. What remains is the correct attribution of all of the lines that you see in red. I am systematically going through the map and fixing all of these. I started at the east end. Don't ask why so many lines are unattributed...long story.

The first image shown here is the extent of the mapping taken to the source vents of the intracanyon lava flows. In this version, only the lava flows and landslide complexes are shown in color. The second image hones in on a small part of the area of detailed mapping (i.e., the river corridor where I have LiDAR and have logged many, many miles of reconn). It has the same color scheme but reveals that there are many other types of units...mainly fluvial deposits.

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State of the Reno / Truckee River map (a small part of it), March 25, 2010

This effort is a compilation / map improvement process. I have been tasked with correlating and refining the Quaternary units in the Truckee Meadows...the large floodplain where most of Reno sits. This process is being enhanced considerably with georectified aerial photos from 1939. And to think, many folks wondered why the airport flooded in the 1997 flood. 

(download)

A serious map...with (surprise!) a dry desert lake

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Yet another map for 2009...don't get too excited, though. I won't
subject you to my rant about how I get surprisingly little credit for
these gargantuan efforts until they are subjected to an external
review...that is for another day. Trust me, it will come. Probably in
mid January.

In any case, this new map includes a snippet of surficial mapping that
I and others did a few years ago in the entirety of Ivanpah Valley,
Nevada...'The Ivanpaviathan' with some minor changes.

The big story here is the huge amount of work that the first author
did in creating the bedrock mapping. This is a complicated area to say
the least (heard of the Keystone Thrust and its ilk?). Larry did a
fair amount of new mapping, but really went the extra mile in
compiling diverse scraps and swaths of mapping created over the years
by the other authors. No small task.

Now, about that missing cross section...

See also: http://geofroth.posterous.com/jean-dry-lake-ivanpah-valley-area-nevada

Yet another map...and another vanished desert lake.

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More on the lake in the desert theme...here is a recently completed,
yet preliminary, map of the terminus of the Carson River where it once
spewed through an amazingly complicated array of distributary channels
that fed a terminal lake in the Carson Desert. The lake was a mere
puddle relative to its ancestor, Lake Lahontan, but it was still
probably pretty cool. It certainly shrank and swelled enough to drive
the river crazy as it built a plexus of channels while chasing its
fluctuating shores.

The 24k scale of this map makes it hard to appreciate the complexity
of the varying river-lake interface. Maybe someday we will map the
whole thing in similar detail...actually, remap it, since Roger
Morrison covered most of this ground in the 50s and 60s. We are just
tackling it with better imagery and slightly improved stratigraphy.

Link to a legible pdf: http://www.nbmg.unr.edu/dox/of0912.pdf

Another new map...with a twist

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Recall when I went on ad nauseum about my struggles with the Lower
Walker River map as I was trying to document (in part) the struggles
that the lower Walker River has had in dealing with its shrinking
lake? If you missed that fun, experience it here:

http://geofroth.posterous.com/tag/walkerriver

Well, I hardly made a peep about this map...mainly because it
was finished earlier and was out of the 'buffer' at the time. But now,
it has reached a comparable state of completion.

The twist with this map (which is along the lower Colorado River
between Hoover and Davis Dams) is that the river has lost its battle
with a lake by virture of having been dammed downstream. Thus, all of
the bluish-greenish units are submerged under the lake.

I was able to map these features with reasonable confidence using
sonar data and large-scale, pre-dam topographic maps of the valley.

Interesting side note: Since getting the map to this point, I have
gotten my hot little hands on a pre-dam aerial photo mosaic of the map
area.

Revision time!

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: