"Hydrologic Engineering Centers River Analysis System (HEC-RAS)" means a hydraulic modeling program developed by the US Army Corps of Engineers to perform one-dimensional hydraulic calculations for natural and constructed channels, which can be downloaded for free at http://www.hec.usace.army.mil/software/hec%2Dras/.
N.H. Admin. Code § Env-Wq 1502.31
(See Revision Note #1 at chapter heading for Env-Wq 1500) #9343, eff 1-1-09