The Castle Rock levee system
Additional images of the levee at Castle Rock from the US Army Corps of Engineers
Sources
http://www.nwp.usace.army.mil/docs/d_msh/Final_Cowlitz_LOP_02-04-10.pdf
http://www.nwp.usace.army.mil/docs/d_msh/Cowlitz_levees_safe_water_level2010.pdf
http://www.nwp.usace.army.mil/docs/d_msh/Toutle-Cowlitz_sediment_budget.pdf
http://www.nwp.usace.army.mil/docs/d_msh/Jun23_2010_mtg_slides.pdf
Some additional resources:
Flood frequency data for the Cowlitz at Castle Rock (xlsx)
Geotechnical data for the Castle Rock levee system
Grain-size analysis for Cowlitz River bottom sediment