Mike,

It sounds to me like you are looking for the procedures implemented in the USGS National Flood Frequency software. The software and associated documentation are available from the following site:
http://water.usgs.gov/software/nff.html

Make sure you get the documentation for the West Virginia equations from the link on that page.

The NFF methods may or may not be applicable to your watersheds depending on their parameters (such as size, etc.), and depending on the purposes of your study. Pay attention to the standard errors of the results - they can be quite large.

The NFF software does not compute water surface elevations, but the flows can be used in hydraulic computations using HEC-RAS or other software tools.

To my knowledge a method applying a multiplying factor to area as the only variable in a linear equation for predicting streamflow has never been in accepted use, but perhaps others on this list have longer memories than I do. The West Virginia equations implemented in NFF use area with a variable exponent so that:

Q(n) = C*A^e

where

Q(n) is the flow for return period n
C is a variable factor, and
e is a variable exponent

The values of C and e vary depending on return frequency and hydrologic
region.

Paul Bijhouwer, PE
Paul.Bijhouwer@parsons.com