USING REMOTE SENSING AND GIS TO TRACK THE MODIFICATION OF FLUVIAL GEOMORPHOLOGY OF THE RIO GRANDE WITH THE INTRODUCTION OF EROSION CONTROL STRUCTURES IN SOUTH CENTRAL COLORADO

In the last decade, erosion control structures have been placed along meanders in the Rio Grande near Alamosa, Colorado. The structures have altered the aggradation and sinuosity of the river. These human changes to the river system can propagate for long distances along the river and alter the course of natural fluvial geomorphology. This study used remote sensing and GIS technology to analyze if some of these changes could be identified, and to determine the impact these control structures have on the natural geomorphology of the Rio Grande.

Using an UAV hexcopter with an independently controlled camera, images were georeferenced, mosaiced and analyzed using ESRI GIS and ERDAS Imagine software. These images were compared with Google Earth historical images to identify any changes before and after the introduction of the erosion control structures.

Public-domain LiDAR images of the area show extensive shifts in the direction and flow of the river, suggesting the lateral flow of the river has a long and complex history in its geomorphology. Initial imagery comparisons suggest that the structures confined the river channel and have either inhibited or slowed formation of oxbow lakes in this area. Measurements of pre- and post- erosion control structures around meanders show that post-structure point bars increased in width by approximately 10-15 meters. Furthermore, inverted pixel analysis of the mosaiced images show that aggradation has increased downstream from where the structures were placed. In addition, raster contours of several images display apparent temporal patterns of sediment/bed load, suggesting that sediment loads change drastically relative to river discharge.

Although aggradation has apparently seasonal variations and responses, it is not clear whether this is a typical accumulation of sediment during spring runoff, or is an effect of the erosion control structures. Further temporal analysis of both past and future images will be needed to more thoroughly understand the processes. Remote sensing and GIS have helped determine small changes within the Rio Grande. However, further testing and research is needed to determine the full extent of the use of such technology in more regional river geomorphology studies.

Session No. 382--Booth# 318

T173. Change Detection Photogrammetry in Earth Science (Posters)

Wednesday, 25 October 2017: 9:00 AM-6:30 PM

Halls 4EF (Washington State Convention Center)

Geological Society of America Abstracts with Programs. Vol. 49, No. 6
doi: 10.1130/abs/2017AM-302142

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