Surface erosion from a forest road, Polk Inlet, Prince of Wales Island, Alaska

• Main Author: Kahklen, Keith F.
• Other Authors: Adams, Paul W., Forest Engineering, Oregon State University. Graduate School
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Soil erosion > Alaska > Prince of Wales Island; Forest roads > Alaska > Prince of Wales Island; Prince of Wales Island; Alaska
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3b591d08d

Rainfall, discharge, traffic, and suspended sediment were monitored for a period of 4.5 months at three locations on a secondary haul road at Polk Inlet, Alaska to determine the important processes and variables involved in surface road erosion for this area. Three sites all less than 500m² and within 5 kilometers of each other on the same road were chosen to be instrumented for monitoring. The proximity of the sites to each other resulted in the sections all being nearly identical in age, topographical location, aspect, elevation, and construction materials. Also, the sites were subjected to the same traffic amounts of approximately 3 to 4 loaded logging trucks per day plus other light vehicles. Maps were developed of the sites which helped determine the source areas for each one. The gradients of sites 2 and 3 were approximately 7%, and the gradient of site 1 was 10%. Each study site was equipped with a flume, pressure transducer, datalogger, and pumping sampler to collect data on discharge and suspended sediment. Sites 1 and 3, had rain gages connected to the dataloggers which recorded 5 minute rainfall intensities. Hourly suspended sediment samples were collected at each site. An infrared traffic counter was used to count the daily traffic amount. An infiltration rate for the road was determined to be 0.9mm/hr using a simple water balance method and also by determining the minimum amount of rainfall to initiate runoff. The infiltration rate was used in development of representative hydrographs for the three sites. The runoff response of the sites were very similar when normalized to an area of 280 m². The precipitation catches for the two gages were very similar with precipitation amounts of 893 mm for site 1 and 975 mm for site 3 during 89 days of record. Several regression analyses were completed for both hourly and storm data to determine which variables and technique would be best for estimating total sediment production. The method that proved to be the best for determining hourly production was to ...