P. D. P. O. Peramuna The HEC-RAS algorithms are restricted to culverts with constant geometry, flow rate, and bottom slope.
HEC-RAS can back-calculate the stage from Manning's Equation given the friction slope, flow, n-value, and cross-section shape. Because it takes relatively little data, normal depth is a frequent boundary condition in both steady and unsteady flow.
HECRAS doesn't provide the depth as direct output. However you can calculate it from 'Profile Output Table (standard table 1) by substracting the Min channel elevation from Water surface elevation. use excel for multiple RS.