This document describes how to generate a drainage line in ArcGIS using spatial analyst and ArcHydro tools. It involves calculating the aspect, flow direction, and flow accumulation from a digital elevation model, then using ArcHydro tools to define streams, segment streams into grids, and convert the stream links grid into vector drainage line features. The key steps are 1) preparing elevation and other raster data, 2) calculating hydrology rasters, and 3) using ArcHydro tools to extract and convert stream networks into vector drainage lines.

1. Drainage generation using ArcGIS
Drainage generation using ArcGIS
Ashok Peddi

3. Add Digital Elevation Model image to ArcMap

5. Open Tools Extensions and verify that the
Spatial Analyst function is available and checked
function is available and checked.

6. Calculate the Aspect using Surface Analysis tool
in Spatial Analyst tools
• Select Spatial
Analyst Surface
Analysis Aspect
Analysis Aspect
on the Spatial
Analyst toolbar. At
the dialog that
appears select
Digital Elevation
Model image as the
input surface.
input surface
• Click on ok .

8. Generating Aspect

10. Calculate Flow Direction
• Assign a flow direction to each grid cell
based on the neighboring cell with the lowest
based on the neighboring cell with the lowest
elevation
• O
Open the Toolbox . Open ArcToolbox, select
h T lb O A T lb l
Spatial Analyst Tools Hydrology Flow
Direction, double click on Fl
Di i d bl li k Flow Direction.
Di i
Give the DEM as Input

12. Flow Direction

13. Calculate Flow Accumulation
Calculate Flow Accumulation
Flow accumulation is calculated from flow
directions.
directions
It calculates the number of grid cells drain into an
individual grid cell
individual grid cell
• With ArcToolbox
With ArcToolbox
open, select
Spatial Analyst
Tools
Hydrology
Hydrology
Flow
Accumulation,
double click on
Flow
Flow
Accumulation

15. Flow Direction
Flow Direction

16. Drainage line processing
Drainage line processing
• Now we will use ArcHydro to
Now we will use ArcHydro to
generate drainage line(if you don’t
have ArcHydero tools for ArcGIS
download it
p
fromhttp://www.crwr.utexas.edu/gi g
s/archydrobook/ArcHydroTools/Tool
s.htm.
• Please close the ArcGIS before
running the Arc Hydro tools. Once
installation process is over please
verify whether the ArcHydro tool
bar is enable or not.
• To verify go to tools and customize
• Check the ArcHydro tools to enable
y
in the ArcMap main window

17. Enabled ArcHydro
E bl d A H d tools
l

18. To generate Drainage line first we need to find out
stream defination using ArcHydro t l
t d fi ti i A H d tools
• Stream Definition
Stream Definition
• This step generates stream grid
from stream accumulation grid.
from stream accumulation grid
• From ArcHydro tool bar, select
Tarrain P
T i Preprocessing – S
i Stream
Definition. Use FlowAcc as flow
accumulation grid, Str as stream
l i id S
grid to be generated.

19. Enter river threshold as per your requirement

21. Stream Segmentation
Stream Segmentation
• Stream segmentation generate a
grid of stream segments from
flow direction grid and stream
fl di ti id d t
grid created from stream
definition processing.
p g
• Input the dialog as following.
FlowDir as the flow direction
grid and Str as the Stream Grid.
grid and Str as the Stream Grid
Output link grid will be Lnk.

23. Drainage line processing
• Thi
This process converts the
t th
stream link grid into a
drainage line feature class that
g
we are familiar with (we
normally represent rivers,
streams as line features).
streams as line features)
• Select Terrain Preprocessing –
Select Terrain Preprocessing
Drainage Line Processing.
Input the dialog as following:

25. • Drainage line is ready.
• End of the document.