1. Watershed and Stream Network Delineation Including Geomorphology
David G. Tarboton

2. Overview
Review of flow direction, accumulation and watershed delineation
Topographic texture and drainage density
Channel network geomorphology and Hortons Laws
Stream drop test to objectively oelect channel delineation threshold
Curvature and slope based methods to represent variable drainage density
The D approach
TOPMODEL
Specialized grid accumulation functions
TauDEM software

3. Elevation Surface — the ground surface elevation at each point
Digital Elevation Grid — a grid of cells (square or rectangular) in some coordinate system having land surface elevation as the value stored in each cell.

4. Direction of Steepest Descent30 30 67 56 49 52 48 37 58 55 22 67 56 49 52 48 37 58 55 22
Slope:

5. Eight Direction Pour Point Model32 16 8 64 4
128 1 2

6. Grid Network

7. Contributing Area Grid1 1 1 1 1 1 1 1 1 1 4 3 1 1 4 3 3 1 1 3 1 1 1 12 1 1 1 1 2 12 1 1 1 2 16 1 1 2 1 16 3 6 1 3 6 25 2 1 2 25
TauDEM convention includes the area of the grid cell itself.

8. Contributing Area > 10 Cell Threshold4 3 12 2 16 25 6

9. Watershed Draining to This Outlet

10. 100 grid cell constant support area threshold stream delineation

11. 200 grid cell constant support area based stream delineation

12. How to decide on support area threshold ?3 12
Why is it important?

13. Hydrologic processes are different on hillslopes and in channels
Hydrologic processes are different on hillslopes and in channels. It is important to recognize this and account for this in models.
Drainage area can be concentrated or dispersed (specific catchment area) representing concentrated or dispersed flow.

14. Delineation of Channel Networks and Subwatersheds
500 cell theshold
1000 cell theshold

15. Examples of differently textured topography
Badlands in Death Valley. from Easterbrook, 1993, p 140.
Coos Bay, Oregon Coast Range.
from W. E. Dietrich

16. Logged Pacific Redwood Forest near Humboldt, California

17. Canyon Creek, Trinity Alps, Northern California.
Photo D K Hagans

18. Gently Sloping Convex Landscape
From W. E. Dietrich

19. Mancos Shale badlands, Utah. From Howard, 1994.

20. Topographic Texture and Drainage Density
Driftwood, PA
Same scale, 20 m contour interval
Sunland, CA

21. Lets look at some geomorphology.
“landscape dissection into distinct valleys is limited by a threshold of channelization that sets a finite scale to the landscape.” (Montgomery and Dietrich, 1992, Science, vol. 255 p. 826.)
Suggestion: One contributing area threshold does not fit all watersheds.
Lets look at some geomorphology.
Drainage Density
Horton’s Laws
Slope – Area scaling
Stream Drops

22. Drainage Density Dd = L/A Hillslope length  1/2Dd B B
Hillslope length = B
A = 2B L
Dd = L/A = 1/2B
 B= 1/2Dd L

23. Drainage Density for Different Support Area Thresholds
EPA Reach Files
100 grid cell threshold
1000 grid cell threshold

24. Drainage Density Versus Contributing Area Threshold

25. Hortons Laws: Strahler system for stream ordering1 3 1 2 1 2 1 1 1 1 1 2 2 1 1 1 1 1 1

26. Bifurcation Ratio

27. Area Ratio

28. Length Ratio

29. Slope Ratio

30. Slope-Area scaling
Data from Reynolds Creek 30 m DEM, 50 grid cell threshold, points, individual links, big dots, bins of size 100

31. Constant Stream Drops Law
Broscoe, A. J., (1959), "Quantitative analysis of longitudinal stream profiles of small watersheds," Office of Naval Research, Project NR , Technical Report No. 18, Department of Geology, Columbia University, New York.

32. Stream Drop Elevation difference between ends of stream
Note that a “Strahler stream” comprises a sequence of links (reaches or segments) of the same order
Nodes
Links
Single Stream

33. Break in slope versus contributing area relationship
Suggestion: Map channel networks from the DEM at the finest resolution consistent with observed channel network geomorphology ‘laws’.
Look for statistically significant break in constant stream drop property
Break in slope versus contributing area relationship
Physical basis in the form instability theory of Smith and Bretherton (1972), see Tarboton et al. 1992

34. Statistical Analysis of Stream Drops

35. T-Test for Difference in Mean Values72
130
T-test checks whether difference in means is large (> 2)
when compared to the spread of the data around the mean values

36. Constant Support Area Threshold

37. 200 grid cell constant support area based stream delineation

38. Local Curvature Computation (Peuker and Douglas, 1975, Comput
Local Curvature Computation (Peuker and Douglas, 1975, Comput. Graphics Image Proc. 4:375) 43 48 48 51 51 56 41 47 47 54 54 58

39. Contributing area of upwards curved grid cells only

40. Upward Curved Contributing Area Threshold

41. Curvature based stream delineation

42. Channel network delineation, other options4 5 6 3 7 2 1 8
Contributing Area 1 2 3
Grid Order 1 4 3 12 2 16 25 6

43. Grid network pruned to order 4 stream delineation

44. Slope area threshold (Montgomery and Dietrich, 1992).

45. Topographic Slope ? Topographic Definition Drop/Distance
Limitation imposed by 8 grid directions.

46. The D Algorithm
Tarboton, D. G., (1997), "A New Method for the Determination of Flow Directions and Contributing Areas in Grid Digital Elevation Models," Water Resources Research, 33(2): ) (

47. Specific catchment area a is the upslope area per unit contour length [m2/m  m]
Upslope contributing area a
Stream line
Contour line

48. Contributing Area using D

49. TOPMODEL
Beven, K., R. Lamb, P. Quinn, R. Romanowicz and J. Freer, (1995), "TOPMODEL," Chapter 18 in Computer Models of Watershed Hydrology, Edited by V. P. Singh, Water Resources Publications, Highlands Ranch, Colorado, p
“TOPMODEL is not a hydrological modeling package. It is rather a set of conceptual tools that can be used to reproduce the hydrological behaviour of catchments in a distributed or semi-distributed way, in particular the dynamics of surface or subsurface contributing areas.”

50. Saturation in zones of convergent topography
TOPMODEL and GIS
Surface saturation and soil moisture deficits based on topography
Slope
Specific Catchment Area
Topographic Convergence
Partial contributing area concept
Saturation from below (Dunne) runoff generation mechanism
Saturation in zones of convergent topography

51. Slope
Specific Catchment Area
ln(a/S) or ln(a/tan) [tan=S] is a wetness index that determines the locations of saturation from below and soil moisture deficit.

52. TOPMODEL soil moisture deficit example
Given
Ko=10 m/hr
f=5 m-1
Qb = 0.8 m3/s
A (from GIS)
ne = 0.2
Compute
R= m/h
l=6.90
T=2 m2/hr
Raster calculator -( [ln(sca/S)] )/5+0.46

53. Contributing Area using D

55. Useful for example to track where sediment or contaminant moves

56. Useful for example to track where a contaminant may come from

57. Useful for a tracking contaminant or compound subject to decay or attenuation

58. Useful for a tracking a contaminant released or partitioned to flow at a fixed threshold concentration

59. Transport limited accumulation
Useful for modeling erosion and sediment delivery, the spatial dependence of sediment delivery ratio and contaminant that adheres to sediment

60. Useful for destabilization sensitivity in landslide hazard assessment
Reverse Accumulation
Useful for destabilization sensitivity in landslide hazard assessment
with Bob Pack

61. TauDEM in ArcGIS Visual Basic ESRI ArcGIS 8.x Toolbar Visual Basic GUI
application
Standalone
command line
applications
C++ COM DLL interface
Available from
TauDEM C++ library
Fortran (legacy)
components
USU TMDLtoolkit modules
(grid, shape, image, dbf, map, mapwin)
ESRI gridio API
(Spatial analyst)
Data
formats
Vector shape
files
ASCII text
grid
Binary direct
access grid
ESRI binary
grid

62. Are there any questions ?
AREA 1
AREA 2 3 12