3.7 | 3 ratings Rate this file 122 downloads (last 30 days) File Size: 107.89 KB File ID: #14504

Flow Accumulation (upslope area)

02 Apr 2007 (Updated 07 Jan 2009)

Flow accumulation algorithm that routes through flats

File Information
Description	How much water flows where? Use this algorithm to calculate the upslope area of each cell in a digital elevation model. Algorithm specifications: - multiple flow direction - single flow direction - routes across flats - calculates deterministic, randomized and random flow - allows you to specify a weighting exponent that governs the relation flow direction - slope - handles edge effects
Acknowledgements	This submission has inspired the following: Strahler Stream Order
MATLAB release	MATLAB 7.0.1 (R14SP1)
Zip File Content
Other Files	example_dem.mat, flowaccumulation.jpg, ixneighbors.m, wflowacc.m

Tags for This File
Everyone's Tags	algorithms, earth sciences(2), elevation, geomorphology(2), hydrology, model
Tags I've Applied
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Comments and Ratings (7)
28 Jun 2007	looks good	looks good
29 Jun 2007	Salvatore Manfreda	Good, but do not have a fill sinks option that would be very useful.
02 Jul 2007	Wolfgang Schwanghart	I did not include a fill sinks option as it requires the image processing toolbox. If you have this toolbox use demfs = imfill(dem,'holes') Best regards, Wolfgang
16 Apr 2008	Jorge Santos Santos	Does not work for large rivers
18 Apr 2008	Wolfgang Schwanghart	Hi Jorge, you are right. The algorithm is quite memory demanding and grids exceeding 600x600 cells may cause problems. I am currently working on an improved version that allows for huge grids. Please be a bit patient... Best regards, Wolfgang
06 Nov 2008	Liam Reinhardt	A good user friendly piece of code. Unfortunately it does not seem to generate single thread 'rivers' 1 cell wide. Instead cells of high accumulation are often adjacent to each other (i.e. perpendicular to the primary flow direction) producing messy flow paths.
10 Nov 2008	Wolfgang Schwanghart	Hi Liam, thanks for your feedback. The code is it stands right now is a multiple flow direction algorithm, and yes, it can be very "dissipative". There is a way to avoid this behavior by element-wise exponentiate the flow direction matrix (M), so that steep gradients gain a larger weight than smaller ones. I'll work on an update of this version and include it as an additional option. Thanks a lot again for the feedback. Wolfgang

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Updates
10 Nov 2008	included single flowdirection and the exponent for flow direction weighting to address the problems encountered by Liam.
07 Jan 2009	an option was added to control flow behavior at grid edges

Tag Activity for this File
Tag	Applied By	Date/Time
hydrology	Wolfgang Schwanghart	22 Oct 2008 09:06:58
geomorphology	Wolfgang Schwanghart	22 Oct 2008 09:06:58
elevation	Wolfgang Schwanghart	22 Oct 2008 09:06:58
earth sciences	Wolfgang Schwanghart	22 Oct 2008 09:06:58
algorithms	Cristina McIntire	10 Nov 2008 11:50:10
geomorphology	Cristina McIntire	10 Nov 2008 11:50:19
earth sciences	Cristina McIntire	10 Nov 2008 11:50:26
model	Cristina McIntire	10 Nov 2008 11:50:44

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