1)Open HEC-HMS.
2)Create a new project.
3)Go to Components→Terrain Data Manager and load the digital elevation model (DEM).
4)Go to Components→Basin Model Manager→Create New Basin→Add Terrain to the basin
(Skipping causes the program to adopt the projection of terrain data set.)
[Sometimes, the terrain might not be displayed properly on the screen although the data is there. This might have happened due to large file size of the terrain.]
5)Go to GIS:
i)Preprocess sinks
ii)Preprocess drainage
iii)Identify stream
The area that we give as an input determines the stream network.
iv)Break point manager (Use it to insert gage point.)
v)Delineate elements:
These prefixes are for naming the subbasins, reaches, junctions, etc.
vi)Merge elements if necessary or you can split as well.
To select two sub-basins, use Ctrl and then, click on it