Remotely Sensed Migration Maps of the Algodones Dunes Southeastern California
Dillon Murphy
MS Candidate
Advisor: Dr. Allen Gontz
Monday Dec. 17th, 2018
CSL 422 – 11:30 am
watch Dillon’s defense
Abstract
Dune migration rates can be extremely variable based on seasonal, decadal, and multi-decadal climate variations. In order to fully understand the migration rates, dune fields must be examined on multiple time scales ranging from hours (individual events), to years (seasonal cycles), to decades (multi-decadal cycles), and longer. Multi-decadal assessments rely primarily on historical aerial photos acquired at infrequent intervals and longer investigations apply techniques of sedimentology and stratigraphy supported by radiometric dating. Newly available remote sensing techniques for assessing environmental change have allowed the use of satellite imagery from Landsat to examine migration rates over the past ~30 years.
California’s Algodones Dune Field is located in the south eastern section of the Salton Trough. Research conducted in the 1980s and 1990s have indicated that the dunes are composed of beach sands derived from former Lake Cahuilla (modern-day Salton Sea) shoreline deposits.
We analyzed daily averaged wind velocities between 1948 and 2017 to establish migration thresholds to determine when the field may have been active. The results of the wind analysis were used to examine periods of time between 1987 and 2018 using Landsat imagery. The imagery was analyzed for change using Cosi-Corr. Analysis of migrations rates are spatially limited due to the 15-meter spatial resolution of the Cosi-Corr and Landsat technique as well as temporally limited based on availability of Landsat data.
Previous researchers have reported a migration rate of 1.0 foot per year using a fifteen-year monitoring period between 1973 and 1987. Wind velocity analysis indicates that this time interval was during a period of enhanced windiness. The Cosi-Corr analysis suggests a higher average of 0.5 meters per year over the 1987-2017 period. The results of this study, when compared with previous research, indicate the importance of variability of driving processes (wind velocity and climate) at short temporal scales. As new satellite data products become available with longer time series and higher resolution (e.g. Planet Labs, 3 m resolution), applications of remote sensing will be able to measure migration rates on shorter time scales and develop a better relationship between event, seasonal, and multi-decadal variation in climate conditions.