WATERSHED ANALYSIS:
GENERATING A WATERSHED MODEL
Gen 314: Geographic information systems
Watershed
•
•
•
A watershed is an area of land that drains all the
streams and rainfall to a common outlet such as the
outflow of a reservoir, mouth of a bay, or any point
along a stream channel (USGS).
Also called as drainage basin or catchment.
Ridges and hills that separate two watersheds are called
the drainage divide.
Animation of water draining from neighboring watersheds.
This pool cover is analogous to a watershed. All of the rain that falls into this area flows
inside of the cover, in this case towards the center. Credit: Howard Perlman, USGS
Fill
Use Flow
Accumulation
Raster
Flow Direction
Flow Accumulation
Raster Calculator
Reclassify Flow
Accumulation
Raster into 2
classes
(“Flow_Acc>= x)
Stream Order
Input stream raster
(raster_calc) and
flow direction
raster
Stream to Feature
and categorize
stream order using
the grid code
Process flow to generate stream networks using DEM (IFSAR)
Create “pour points” on the
flow accumulation raster
Define the Pour Point IDs
and save your edits
Start editing and digitize the
lowest point along flow
accumulation zones
Stop Editing
Start Editing
Add a new attribute
column in the pour points
layer and have it renamed
as Pour_Point_ID
Environments>processing
extent> same as the flow
direction raster
Raster to Polygon
Watershed
> Input flow direction raster
> Input pour point data
>Select the pour point ID
field
Process flow to generate a watershed model using DEM
Aja!