Data flow
Workflow
(download the workflow diagram for better resolution)
Profile extraction
Sink filling
1. Fill sinks in original DEM (ArcToolbox > Spatial Analylst > Hydrology > Fill)
2. Create Flow raster using D8 algorithm of Hydrology toolset (ArcToolbox > Spatial Analylst >
Hydrology > Flow Direction)
3. Create Flow Accumulation raster (ArcToolbox > Spatial Analylst > Hydrology > Flow
Accumulation)
4. Delineate watershed (ArcToolbox > Spatial Analylst > Hydrology > Watershed)
5. Convert watershed to a VECTOR from a RASTER using (ArcToolbox > Conversion > From Raster >
Raster to polygon )
6. Convert to shapefile and remove fill color by clicking on layer’s color bar in legend
Maximum Flow path
To calculate Flow length (ArcToolbox > Spatial Analyst > Hydrology > Flow Length)
To calculate the Maximum value (ArcToolbox > Spatial Analyst > Zonal > Zonal Statistics as table)
Pick (hopefully, since float and not integer raster) one
Don’t forget to change output raster path to the same folder.
(ArcToolbox > Spatial Analyst > Map Algebra > Single Output Map Algebra)
I don’t see that cell ! (Optional)
(ArcToolbox > Conversion > from Raster > Raster to Point
Longest flow path
(ArcTool box > Spatial Analyst > Distance > Cost path)
Either
or
I prefer former.
Profile extraction
To extract profile, we will add Z coordinate from DEM and distance along the line to our flow path.
However, beforehand let’s convert our longest flow path to polyline and limit it by watershed
boundaries.
(ArcTool box > Conversion > from Raster > Raster to Polyline)
(ArcTool box > Analysis > Extract > Clip)
At this point we have polyline within watershed boundaries.
(go to bottom of ArcTool Box > Search > Interpolate shape – it should be in 3D)
Create Routes
(go to bottom of ArcTool Box > Search > Create Routes – it should be in Linear Referencing Tools)
(go to bottom of ArcTool Box > Search > Write Features to Text)
Import profile.txt into Excel
Delete first line, rename columns and add scatter plot for Problem 2.
Forward difference will give you a good slope approximation for Problem 4
The last value in the distance column is an answer for Problem 1.
Use Filter to extract 10% to 85% slopes into separate sheet. Use average function for Problem 4.
Problem 5c - Streams Network
Flow accumulation
If you didn’t do it yet it is time.
Flow accumulation threshold
Define flow accumulation threshold (the easiest way) for stream formation. We can clip our streams the
same time. Watershed == 0 will also work.
Enumerate all streams
Now you can optionally use unique values for each stream
Rank streams
Convert to poly lines
Change symbology to see different colors for different stream orders
Problem 5d
Total network length to watershed ratio
Add field for length
Right click on new column and click on calculate geometry
Right click on that new column again and select “Statistics…”. You should be able to see sum of all
stream lengths.
I got 42041 meters total streams length for 10,000*8.6*8.6 flow accumulation threshold.
Now you can calculate ratio using total watershed area that you calculated earlier.
Hypsometric curve
Clip your DEM
Export attributes table from dem_int
Open in Excel, rename columns, calculate cumulative area