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AEG, SWES, HWRSA and NRGSO students will be teaming up to conduct LiDAR scanning of the upper Rincon Creek watershed for research related to wildfire management issues. According to park biologist Don Swann the watersheds below Rincon Peak have not seen fire in possibly over 100 years due to fire suppression management of the forest. With the increases in recent forest fires throughout the southwest US and post-fire debris flows associated with them, Saguaro National Park needs to know what the hazards are before it burns and it is too late to do anything. Recently other regional mountains have burned and have had post-fire debris flow assessment and modeling done to predict probabilities of failure and volumes of debris. It is hoped that the overly forested watersheds of Rincon Creek can be assessed pre-fire in order to facilitate proactive management of the forest if the hazards are too great to people, infrastructure and natural and cultural resources.
Long-range terrestrial LiDAR will be used to extract 3D point cloud images of the main upper watersheds on Rincon Peak. The group will hike up to Happy Valley Saddle, camp out and then hike to optimal vantage points within 1.5 kilometers (the range of the Optec scanner) of the watersheds to conduct scanning. Scans will be primarily horizontal or looking slightly up at the slopes to try to see under some of the forest canopy and under overhanging rock surfaces. Since Saguaro National Park East already has airborne LiDAR data, the terrestrial LiDAR point clouds will be merged with them to produce 3D images with good data coverage from above and below. This merged point cloud should be optimal in conducting debris flow analysis, and hopefully other natural resource and environmental research related to the watershed.
Below is the informal proposal I gave to Saguaro National Park regrading this project.
- What does the sampling equipment look like?
Our equipment is shown below in Figure 1, which includes scanner, tripod, camera and batteries. Also shown in image are some LiDAR results from our last research project.
Figure 1. a) Google map showing sequence of scans performed, b) our Optec LiDAR scanner with high resolution digital camera mounted on top, c) greyscale 3D scan image, d) color 3D scan image due to draping the high resolution photo onto the LiDAR point cloud.
2. How long do you sample for?
We usually scan for about 4 to 6 hours depending on the area we’re trying to cover.
3. How do you relate the data from this instrument to our Lidar data from
the air (which we have for the whole park now)?
We can stitch the terrestrial point cloud to the airborne and create a more detailed, multi-perspective model of the slopes and watershed we are trying to assess. Merging the terrestrial image with the airborne image gives more complete data for places shadowed from the air like under trees and under cliff ledges, so that the ground surface can be better assessed. Below in Figure 2 and 3 are examples of this in Yosemite National Park.
Figure 2. Merged Airborne and Terrestrial LiDAR point cloud images (Stock et al., 2011)
Figure 3. Surface model produced from LiDAR image and draped high resolution photograph (Stock et al., 2011)
4. What would the resulting product look like (e.g., what could you send
to us as a product?)
Figures 1, 2 and 3 are examples of products we could deliver for this project by this summer if we scan this spring. In addition to these products, other possible products we could deliver would be: geologic stereonets of the structure and jointing, DEMs, slope stability and rockfall modeling results, debris flow hazard analysis. These last products would take much more time and expertise than the basic scan images, which already take some time and skill to produce, so they would probably be either based on graduate student research projects or over long periods through club volunteers. We could also enlist our other collaborating clubs to work on this with us, which include SWES (Soil, Water and Environmental Science), HWRSA (Hydrology and Water Resources Student Association) and NRGSO (Natural Resources Graduate Student Organization). They could use the scanning results to conduct studies on the soils, vegetation and hydrology of the area. Scans can be done over consecutive time periods and merged together to conduct a change detection map, where topography that has changed (including plants and other structures) is colored red where for removal or loss and blue for deposition or growth. These are just some ideas I have for how it could help.