Landslide Susceptibility and Soil Loss Estimates for Drift Creek Watershed, Lincoln County, Oregon

ABSTRACT Drift Creek watershed, Lincoln County, Oregon, is a source of drinking water as well as a reproductive habitat for endangered salmon and trout species. Landslides, exacerbated by logging, are suspected as a cause of water quality deterioration in the watershed. To investigate the impact of landslides on water quality, we mapped landslide distribution and susceptibility, determined engineering properties of landslide-prone soil and rock, and estimated soil loss resulting from landslide-derived sediment within 30 m of Strahler third-order-or-higher streams in the watershed. We mapped 570 landslides using LiDAR imaging, orthophotographs, and field observations. We used logistic regression to determine the most significant variables contributing to landslide occurrence and to create a watershed-scale landslide susceptibility map. Siletz River Volcanics and the sedimentary Tyee Formation make up 85 percent of the watershed, with the sedimentary Yamhill and Nestucca formations making up the majority of the rest. Sedimentary rocks dominate in the Upper Drift Creek watershed, and volcanic dominate in the lower portion. The largest landslide deposits and the highest susceptibility occur in the sedimentary rock formations. The Siletz River Volcanics has a larger abundance of landslides than the sedimentary rock formations, but they are smaller in size with lower susceptibility of occurrence. The soil loss model indicates that the average annual soil loss from landslide deposits in the Upper Drift Creek watershed is 65 tons/acre/yr compared to 29 tons/acre/yr in the Lower Drift Creek watershed. The model also indicates that soil loss from areas along roads in the watershed is high.

Improved Change Detection with Trajectory-Based Approach: Application to Quantify Cropland Expansion in South Dakota

The growing demand for biofuel production increased agricultural activities in South Dakota, leading to the conversion of grassland to cropland. Although a few land change studies have been conducted in this area, they lacked spatial details and were based on the traditional bi-temporal change detection that may return incorrect rates of conversion. This study aimed to provide a more complete view of land conversion in South Dakota using a trajectory-based analysis that considers the entire satellite-based land cover/land use time series to improve change detection. We estimated cropland expansion of 5447 km2 (equivalent to 14% of the existing cropland area) between 2007 and 2015, which matches much more closely the reports from the National Agriculture Statistics Service—NASS (5921 km2)—and the National Resources Inventory—NRI (5034 km2)—than an estimation from the bi-temporal approach (8018 km2). Cropland gains were mostly concentrated in 10 counties in northern and central South Dakota. Urbanizing Lincoln County, part of the Sioux Falls metropolitan area, is the only county with a net loss in cropland area over the study period. An evaluation of land suitability for crops using the Soil Survey Geographic Database (SSURGO) indicated a scarcity in high-quality arable land available for cropland expansion.

An opalized oak from Clover Creek, Lincoln County, Idaho c.1895

According to mineralogical literature, some of the finest opalized wood in the world was discovered in Idaho c.1895, originating in a unique deposit along Clover Creek in Lincoln County (now Gooding County). The American mineral dealer Dr A. E. Foote acquired and processed the bulk of the discovery into specimens that were advertised between 1896 and 1904. Over a period of four years, we have identified sixteen natural history museums in Europe, North America, and Australia in possession of Clover Creek opalized oak today. Many museum acquisitions and the fossil’s taxonomic affinity, Quercinium pliocaenicum, resulted from collective networking between mineral dealers, private collectors and scientists – evidence of a common interest among a diversity of people – contributing the best specimens for museums of natural history.