land to hecras

EXPORTING LAND DESKTOP DATA INTO HEC-RAS

Geometric data can be taken from Land Desktop and exported to a text file which can be loaded
directly into the Hydrologic Engineering Center – RiverAnalysis System (HEC-RAS). You must
have a terrain model set up that the program will use to extract data. From that, it will be sent to
HEC-RAS. The terrain model can use data from detailedtopographic surveys, Digital Elevation
Models (DEM), or manually digitized contours.
1. The first step is to define the
locations of the sections that will be
exported into HEC-RAS. Sections
can be drawnusing lines or 2-D
polylines with a maximum of three
vertices (one change in direction). In
this example, the section lines are
drawn on top of a United States
Geological Survey (USGS) rasterimage to help orient where the
sections should go. The raster image
lines up with a DEM file which will be
used to obtain geometric information
which will be exported to HEC-RAS.
Keep in mind thatHEC-RAS geometric information is entered from left to right when looking
downstream. This is important when defining sections using polylines because the end on
which you start your polyline will bethe side that Land Desktop will use to begin the section.
This means that if you draw your polyline from right to left instead of left to right, your section
will import into HEC-RAS backward. Thisis less important with lines because Land Desktop
will start the section on the end of the line nearest to where you select it, without regard to
which direction the line was drawn.
If you areworking in an area where
the channel geometry does not make
it possible to line up a section
perpendicular to the stream channel,
you can place one intermediate
vertex in your section line such aswith section 110 on the left.

2. After you have drawn in the locations of the sections that you
want to export, go to HEC2 Output, HEC2 Single, under the
Hydrology drop-down menu. You may need...