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Title: Using Cesium-137 to study soil redistribution in Guam and Hawaii

Author
item Ritchie, Jerry
item PEDONE, PAUL - USDA, NRCS, PORTLAND, OR

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2008
Publication Date: 12/12/2008
Citation: Ritchie, J.C., Pedone, P. 2008. Using Cesium-137 to study soil redistribution in Guam and Hawaii [abstract]. South Pacific Environmental Radioactivity Association Conference. 2008 CDROM.

Interpretive Summary:

Technical Abstract: Understanding soil redistribution and sediment sources on the landscape are keys for the development of management strategies for reducing soil erosion and the delivery sediments to floodplains, streams and water bodies. Fallout Cs-137 has been used extensively to measure soil redistribution, to determine floodplain deposition patterns and rates, and as a tracer or fingerprint to identify sediment sources within a watershed. The objective of this study was to use Cs-137 to study soil redistribution patterns on the landscape and to determine the source of sediments in Guam and Hawaii watersheds. Soil samples were collected from the various geomorphic surfaces and floodplain deposits within the Hanalei River Watershed in Kaua’i, Hawaii and in Guam and analyzed for Cesium-137 concentration. Recently deposited sediments on floodplains in both regions showed significant deposition in the last 50 years. In the Hanalei Bay watershed, Cs-137 concentration varied with upland soils > colluvial slopes > floodplain deposits > stream banks > Bay sediments. Preliminary results using a simple mixing model to determine sediment sources indicate that stream banks and mass wasting are probably the most significant sources of sediments deposited on the floodplains and in the Hanalei Bay.