HEC-1

The US Army Corps of Engineer's Hydrologic Engineering Center (HEC) has been involved in the development of computer simulation models for several decades.  One of their most popular models has been HEC-1, which is a deterministic model used to model runoff from rainfall.  The HEC-1 (which is now HMS) model includes several different methods for defining rainfall, losses, runoff transformation and routing.  HEC-1 is divided into separate hydrograph computational units as illustrated in the diagram below.

The most simple hydrograph analysis problems are solved with a single basin.  For a basin, runoff is computed from a defined rainfall depth and temporal distribution, a loss coefficient, and a runoff transformation method.  The way these three processes are simulated in a deterministic model will be discussed in the following pages.  For more advanced analyses a computed basin hydrograph can be routed through reaches, reservoirs, and diversions to produce the resulting downstream hydrograph based on the channel, reservoir, or diversion properties.