Examination of Hydrologic Computer Programs DHM and EDHM

Abstract

The Diffusion Hydrodynamic Model or DHM is a coupled one- and two-dimensional (2-D) surface flow model based upon a diffusion formulation of the well-known Navier–Stokes equations, developed by research hydrologists of the USGS (United States Geological Survey) for use in modeling floodplains and dam-break situations. The Fortran 77 source code and various applications were published in 1987 by the USGS as a Technical Report authored by Hromadka and Yen. The DHM program led to the development of several subsequent computational programs such as the FLO-2D computational model and other similar programs. The original DHM program had a limit of applications to problems with no more than 250 nodes and modeling grids. That limitation was recently removed by a program version named EDHM (Extended DHM), which provides for 9999 nodes and grids. However, the computational code is preserved in order that the baseline code algorithmic procedures are untouched. In this paper, the DHM and EDHM are rigorously compared and examined to identify any variations between the two Fortran codes. It is concluded from this investigation that the two sets of algorithm codes are identical, and outcomes from either program are similar for appropriately sized applications.