Transcript No Slide Title

A tool to delineate watersheds and river networks
for multiple sites spread over large Digital
Kiran Chinnayakanahalli , David G. Tarboton
Elevation Models
*
Civil & Environmental Engineering Department, Utah State University, Logan, UT
John Olson, Ryan Hill, and Chris Kroeber
Department of Aquatic, Watershed, and Earth Resources, Utah State University, Logan, UT
*Email:
[email protected]
Abstract
Geographic Information Systems (GIS) methods for watershed and stream network delineation are based on the derivation of flow
direction and flow accumulation from Digital Elevation Models (DEM). This method can be laborious when the number of
watersheds to be delineated is large, as one has to fill sinks in DEMs, process flow direction and flow accumulation for each site
being delineated. Further, if the site location is not exactly on the digital representation of the stream, GIS based methods will result
in the wrong watershed boundary. Additionally, when the sites are spread over relatively large geographical area, DEMs and other
raster datasets necessary for watershed delineation, because of the chosen resolution, can be large and are not handled well by
the currently available watershed delineation tools. This work will present a standalone Windows program based on the
functionalities of ArcGIS and TauDEM that is specifically designed to delineate multiple watersheds spread over large raster data
sets, and has functionalities to move the site locations to the nearest streams based on the flow direction grid, if they are not
already present on the stream. This tool uses USGS hydrologic units as regional watersheds to sample the grids and then
delineate watersheds draining to sites located within each regional watershed in a batch process. This tool also provides options to
delineate watershed based on contributing area or a curvature approach that better reflects variable geomorphology, and can
objectively choose the appropriate threshold to delineate stream networks based on the constant drop test. Additional capabilities
of this program include the computation of geomorphic variables such as hypsometric curve indices, shape factors, stream network
geomorphology attributes, and average watershed properties from input grids. This tool is useful in deriving watersheds, stream
networks and watershed attributes of importance to a variety of problems in hydrology, stream ecology and geomorphology.
The challenge
-Delineate and derive watershed
attributes for a large number of
watersheds
-Outlet points do not always
coincide with streams (Fig 1)
-DEM too big for processing
Correct position of
site on the
all watersheds at once (Fig 2) the
stream results in the
-178 sites
-at a 30x30m cell size it
has 16008 X 18594 grid
cells
Slightly offset position of the
site leads to the incorrect
watershed boundary
Sites (178)
Utah state boundary
&
correct watershed
boundary.
Sites (178)
0
Fig 1: The effect of the
site/outlet off the stream,
on watershed delineation
100
150
200
Kilometers
Utah state boundary
Fig 2: A typical data set for the use in Multiwatershed Delineation (MWD) tool
Standard watershed and stream
delineation recipe
0
25 50
100
150
200
Kilometers
Regional watersheds used in cutting grids
(8 digit HUC)
Site which is
delineated from
the sampled grids
- Vector stream (ex. NHD data) fusion into
DEM raster (burning in)
- Sink removal
- Flow direction
- Flow accumulation
- Stream identification
- Vector and attribute extraction
Sampled grids
Buffer
Original grids
Solution
•Buffer and cut grids (Fig 3) using regional
watersheds (8 digit HUC)
•Preliminary stream network mapped using
support area method
•Move outlets down slope to place on
nearest stream
•Drainage density and stream network
mapped using constant drop test.
•Delineate watershed boundary
•Compute watershed attributes
25 50
Flow accumulation
grid
Flow direction grid
Sink removed DEM
DEM
Fig 3: Grid cutting using regional
watersheds
INPUT
Shapefiles
-Regional watersheds
(polygons)
-Sites or outlets
(points)
OUTPUT
Raster/grids
-DEM
-Sink removed DEM
-Flow direction grid
-Flow accumulation grid
-Stream grid
Fig 4: Multiwatershed delineation (MWD) program
Files
-Watershed boundary
-Stream network
A standalone program that
uses TauDem and
ArcObjects functionalities
with a visual basic interface
Other features
-Options for drainage delineation
Attributes
methods
-Watershed area
a) Curvature based method
-Elevation statistics
b) Support area method
-Hypsometric curve indices
-Constant drop test for objectively
-Drainage density
choosing the threshold for
-Watershed shape factor
delineation
-Zonal statistics tool for sampling
other raster datasets (climate,
soil, geology etc) over multiple
watersheds.
Fig 5: Output from the Multiwatershed delineation program
APPLICATION
We developed this program to allow us to
efficiently derive physical properties for
thousands of watersheds and sample sites.
Hydrologic
indices
Climate
Watershed
morphology
Soils
500
=f
This tool is used to derive watershed boundaries
and attributes for sites in the Western United
States for
BFI
DAYCV
-developing statistical models to estimate
QMEAN
Q1.67
ZERODAY
stream flow regime variables at ungauged
Colwell’s index
7Qmin
basins by relating them to watershed
7Qmax
NOR
attributes (Fig 6)
Flood frequency
-for classifying streams and rivers using
different classification schemes (ex.
Response
Geomorphologic, geologic, hydrologic etc)
variables
400
300
200
100
0
1957 1958 1959 1960 1961 1962 1963 1964 1965
,
,
Mean annual
Watershed area
precipitation
Main channel length
Monthly mean
Main channel slope
temperature
Mean elevation
Monthly max and
Relief
min temperature
Drainage density
Basin shape
Hypsometric
curve indices
Outlet elevation
Soil thickness
Available water
capacity
Permeability
Bulk density
Explanatory variables
Computed using MWD program
Derived using zonal statistics tool within
MWD program
Fig 6: Example of MWD tool use in deriving watershed attributes
for building statistical models to estimate stream flow regime variables at ungauged sites