A Simple Drainage Enforcement Procedure for Estimating

Catchment Area Using DEM Data

David Nagel, John M. Buffington, and Charles Luce

U.S. Forest Service, Rocky Mountain Research StationBoise Aquatic Sciences Lab

Boise, ID

October 20, 2011

Study Area

10,000 km of rivers and

streams

~ 1,000 km used by salmon

Middle Fork Salmon River

Our Purpose Estimate catchment area

Discharge

Grain size

Salmon spawning habitat

Data

10 m NED DEM dataset

NHD stream lines

http://ned.usgs.gov/

http://nhd.usgs.gov/

Problem

Flow accumulation lines from DEMs do not match vector stream lines

NHD stream

DEM flow line

Drainage Enforcement Objective

Recondition the DEM so all cells drain toward the stream and downstream

Non-enforced Enforced

Foundation of Watershed Analysis1) Fill

2) Flow direction

3) Flow accumulation

Fill Direction Accumulation

Flow Accumulation

Counting up the number of cells that contribute to a location on the stream = catchment area

1,00012,000

Raster Accumulation to Vector

Raster accumulation

12,000 cells

Attribute corresponding vector

Mismatch Between Raster and Vector Without Enforcement

EnforcedNon-enforced

Can’t attribute vector if data are mismatched

Why the DEMs and Stream Lines Do Not Match in Flat Valleys

DEM Production Process

1) Aircraft 2) Aerial photo 3) Stereo plotter

4) Map production 5) Scan and tag 6) LT4XLT4X, Infotec Development, Inc.

Original Contours and 10 m DEM Model

Original 40’ contours 2 m contours derived from 10 m DEM

LT4X

Blue box = 100 m x 100 m

500 m

Original Contours and 10 m DEM Model With Streams

Original 40’ contours 2 m contours derived from 10 m DEM

LT4X

LT4X made the DEMs from the original contours

There were no contours in flat valleys, so there wasn’t information for generating

the DEM data

Cartographers drew stream lines where they saw them,

independent of the LT4X model

Why Not Use LiDAR?

Site scale vs. landscape scale

Drainage Enforcement Algorithms1) ANUDEM - ArcGIS

2) AGREE – Arc Hydro Tools

3) IDDEA – Forest Service

ANUDEMImplemented by ArcGIS

(Topo to Raster)• Not designed for reconditioning DEMs directly -

requires contour lines or point input• Contour file sets may become too large• Avoids “trenching”

Hutchinson, M.F., 1989. A New Procedure for Gridding Elevation and Stream Line Data with Automatic Removal of Spurious Pits. Journal of Hydrology, 106:211-232.

AGREE Algorithm Implemented by Arc Hydro Tools

Dewald, T., NHDPlus User Guide, U.S. EPA and USGS, April 29, 2008

Hellweger, F., 1997. AGREE — DEM surface reconditioning system. Center for Research in Water Resources

Drainage Enforcement with AGREE

Original Reconditioned• Arcs must point downstream• Sharp drop may modify watershed boundaries• Uses “trenching”

IDDEA MethodInverse Distance Drainage Enforcement

Algorithm1) Grid stream lines2) Generate Euclidean distance from all stream lines3) Drop stream by constant value (e.g. 200 m) and4) Invert distance, multiply by constant: (1/d) * 1000 5) Subtract result from original DEM

Where cij, 200, else eij – ((1 / dij) * 1000)

cij is a stream channel cell at raster location ijeij is the elevation at ijdij is the Euclidean distance at ij

1) Grid Stream Lines

Vector to raster conversion

2) Euclidean Distance from Streams

3) Inverse Euclidean Distance

• Force constant drop (200 m) at stream channel• Enforcement decreases away from the

channel

(1/d) * 1000

200

0.02

200100

5010

0.1

Value decreases(unitless)

DEM Minus Inverse Distance

minus =

Profile Results

Preserves relative topography and

watershed boundaries

Run Flow Accumulation

Enforced

Non-enforced

Attributing Vectors

EnforcedNon-enforced

Higher probability of accurately attributing vectors with the correct contributing area

Results Comparison

0 100 200 300 400 500 600 700 800 900 10000

100

200

300

400

500

600

700

800

900

1000f(x) = 0.998441428124002 x + 7.68333422256683R² = 0.999863789909996

Catchment Area Comparison

IDDEA Catchment Area (HA)

Non

-enf

orce

d C

atch

men

t Are

a (H

A)

Disadvantages of the IDDEA Method

1) “Trenches” the DEM2) Meander bends smaller than cell size get

cut off and reroute flow

“Trenching” Cut-offs

Advantages of the IDDEA Method

1) Works relatively quickly at landscape scales

2) Preprocessing of raster or vector data is not required

3) Preserves relative topography and watershed boundaries

Thank you