07-09-18 Drainage and Flooding Committee Meeting

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IML Texas Commission on Environmental Quality (TCEQ) Coordination The coordination with TCEQ may be necessary to determine the need for Municipal Separate Storm Sewer Systems (MS4) permit. This report did not evaluate the MS4 requirements as it is outside the defined scope. 3. Existing Conditions Drone Data Collection The use of aerial photogrammetry for data collection of the pavement condition was based on trends in the industry for increasing use of remote data collection, coupled with increased visual capability of photogrammetry due to increasing camera resolutions allowing for tighter (less than '/4 inch pixel resolution) imagery. The use of hyper -spatial resolution (sub -centimeter or sub -inch) natural color aerial photography (HSR-AP) was studied by the University of New Mexico and a document was published in May 20168 outlining the results of aerial data imagery and 3D surface modeling captured aerially and comparatively studied on the ground by conventional methods with a comparison of the two methods. A sensitivity analysis was made on the results of the two methods and the data collected for rut depth, alligator cracking, and transverse cracking of flexible pavement in various sites in New Mexico. The results of the sensitivity analysis showed that the differences in measures between the aerially derived measures and the ground measures were not statistically different, even at a 95% confidence level9. Because of this accuracy, we proposed and collected data aerially to evaluate the pavement condition and quantified pavement deterioration for rehabilitation on this project. The aerial data collected for this report was gathered by two unmanned aerial vehicles. The first (for 3D model derivation) is an Ebee fixed wing aircraft. This aircraft gathered topographic information to derive a surface model of the site to use with the drainage investigation. This platform also gathered a low -resolution (comparable with Google Earth) imagery, but of the entire project area. The second aircraft was a DJI Phantom quadcopter by Parrot. This aircraft collected much higher resolution imagery to document pavement distress for condition assessment and quantity calculations of pavement rehabilitation. Conventional Survey Collection Some data for the drainage investigation was not able to be obtained by remote means. For this, the conventional on -the -ground survey was used for measuring features like silted -in culvert flowlines and ditch and swale elevations that were below 8 Characterizing Pavement Surface Distress Conditions with Hyper -Spatial Resolution Natural Color Aerial Photography by Zhang, Leppitt, Bogus, Neville, et al (University of New Mexico) republished by Remote Sens. 2016, 8, 392. 9 Ibid, pg 14 of 23. Page 18