Screenshot that shows the current status of my mapping in a key area. Landslides are green and broken into three relative ages (brighter=younger). Red lines have not been attributed yet. Map is coming along nicely.
Wednesday, September 30, 2009
Geologic Map of the central Hole in the Ground area, Owyhee River, OR
Tuesday, September 29, 2009
Owyhee Mapping Project: All traverses by your pal, Kyle.
Ok, so maybe I spent enough time out there in 2007, 2008, and 2009. Yikes. As expected, the parts of the map that are the hardest to compile in the office are those areas I never hit on the ground.
My 2009 field traverses in the Owyhee River study area
Yes. I am a little late on getting my NSF annual report done...why these are due 3 months before the end of the year in question is beyond me. Most annual reports are due within 3 months of the end of the contract year. I suspect that someone made a mistake in the original paperwork and simply won't own up to it.
Anyway, getting the report together has given me a chance to organize my field data more completely. Here are the traverses from this year. This includes the group trip in late May, my field camp stint in early June, and a solo trip in August.
The utterly obvious concept of making a traverse map is made very simple with a Garmin 60csx, the DNR Garmin (free) software, and ArcGIS. But, hey, you already knew that because you record all of your field traverses that way, right?
LiDAR-derived contours are useful, too.
Sure, I have gone on and on about the amazing visualizations you can get with some tweaking of LiDAR data; however, it turns out that a pretty basic representation is also quite useful...contours. Yes, contours. Sometimes smaller scale features remain somewhat ambiguous in hillshades or slopeshades, but high-res, short interval contours from the LiDAR data can eliminate most of the ambiguity. In this case, it is a tiny area that I have struggled with on the Owyhee River. Here, a large landslide entered from the north, shoved the river channel to the south, and the river eventually worked its way back to the north to some extent. The array of surficial deposits in the void that comprises the right hand side of the image south of the river record this sequence of events as well as subsequent sedimentation by tributary fans. The contours really highlight the fans, and in conjunction with discernible drainage patterns evident in the LiDAR, it is clear what is fan and what is river, right?
2-m Contours were generated in GlobalMapper and exported as shapefile to view in Arc.
Note, Ian Madin (at DOGAMI) gave me the tip on contours especially as they relate to resolving fan features. He was right...it works!
Extent of lake caused by the Greeley Bar lava dam
I created this lake by generating a contour from the LiDAR dataset at an elevation of 1046 m. GlobalMapper does this in about 1.5 minutes. Then, exported the vector as a shapefile, cut out the parts of the line that occur downstream from the dam, stitch the remaining loose ends, build a poly from the line and there it is.
This lake has an interesting topographic correspondence with the old landslides on the south side of the Hole in the Ground as well as the ancient fan remnants that come in from the north side. Don't forget that much of the topography you can see through the lake didn't exist at the time of the lava dam. The valley floor was probably formed on the Bogus Rim lava which forms the flat-topped features that flank the left and right banks of the river near the eastern end of the lake. The top of the Bogus Rim lava is only about 25 m below the surface of this lake. Thus, the link between this lake and the landslides is dubious as there was nowhere for the landslides to slide.
Plausible extents of landslide-dammed lakes in The Hole in the Ground
I have developed polygons showing likely extents of lakes related to both lobes of the Doublespring Landslide Complex on the Owyhee River. Using a combination of LiDAR data, ArcGIS, and GlobalMapper in conjunction with the highest plausible geomorphic evidence of fluvial overtopping the following lakes result:
East Spring Landslide: 878 m lake elevation.
West Spring Landslide: 868 m lake elevation.
(it is possible that both are a few meters low...need some field data)
The correspondence / lack of correspondence of these lakes with various upstream landforms and deposits is surprising.
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