13
votes
Accepted
Methodology for creating accurate drainage networks (and catchments) from high resolution LiDAR DEM?
Have you consider to use GRASS GIS analysis? I have expirience that GRASS algorithms have very good accurance on hydrology analysis. For example, I want to generate something like drainage network on ...
- 1,773
11
votes
In hydrologic terrain analysis is there a difference between "pits", "depressions", and "sinks"?
There is a difference, and I recommend the typology presented by Lindsay (2015) be used.
Lindsay (2015) presents a typology which defines a pit as a single cell in a DEM whose elevation is below that ...
- 1,801
10
votes
Accepted
Calculating width of unusually shaped polygon in QGIS
Find the centerline using v.voronoi.skeleton
Create points along the centerline (Points along geometry)
Create perpendicular lines to the points with Geometry by expression:
extend( make_line( $...
- 63.8k
9
votes
Accepted
How to run a tool from Whitebox GAT in ArcGIS?
I'm afraid that when I wrote Whitebox GAT, I never really anticipated that there would be a demand to be able to run the Whitebox plugin tools from outside the user interface. I knew that there would ...
- 11k
9
votes
Accepted
Calculating average stream slope at each location along stream using ArcGIS Desktop?
As @Hornbydd pointed it is network searching problem. I suggest the following workflow:
find source points of the streams
sort them in descending order by flow length
In the picture below 139 green ...
- 22.4k
9
votes
Accepted
Lowering density of GRASS r.stream.extract result?
You need to adjust the "threshold" parameter, which is Minimum flow accumulation for streams in the Processing GUI. With this parameter you determine what is the minimum drainage area for each stream ...
- 15.3k
8
votes
Accepted
Extract river polygons from DEM
One approach that our amazing intern recently used, which turned out really well for us:
Fill the DEM
Calculate flow direction on the filled raster
Accumulate the flow of the flow direction output
Do ...
- 4,108
7
votes
Accepted
Does this ArcGIS flow accumulation example have an error?
It is an error. Your link and presumably image source is the 10.0 help. The error is still present in the 10.1 help. However in the 10.2 help, it has been corrected to show only a 1.
It's also worth ...
- 15.6k
7
votes
Flow Direction created from depressionless DEM inaccurate in flat areas
These are common problems, typically resolved by stream burning, but that relies on you having a vector network to enforce drainage. I recommend you check out the free GIS software Whitebox GAT it has ...
- 41.8k
6
votes
Ways to determine winding topographic characteristics of a river
In the world of hydrology and geomorphology, there is indeed a metric that we use to classify/quantify the "curviness" of a river......sinuosity.
Sinuosity is simply a measure of the actual path ...
- 61
6
votes
Accepted
Delineating multiple nested catchments in R whitebox; prevent primary catchment from being cut by subcatchment
This scenario is precisely what the WhiteboxTools UnnestBasins tool is used for. The tool documentation states:
In some applications it is necessary to relate a measured variable for a group of ...
- 11k
5
votes
Identifying highs on DEM using ArcGIS Spatial Analyst?
One easy way of doing this would be to inverse your DEM by multiplying it by negative one (Raster Calculator) then running the Fill tool on the inverted DEM. Finally, subtract the filled DEM from the ...
- 11k
5
votes
Accepted
Choosing parameters for SAGA Wetness Index?
After lots of calculations and experiments I think I can (at least partly) answer my own question:
Suction: according to the source code (Conrad 2014), a suction of 10 is "average", a smaller value, ...
- 173
5
votes
Accepted
Isochrone along direction map of watershed
Here how "Isochrone Variable Speed" from SAGA works:
First you need to load your filled DTM into SAGA
Then you need to run the "Slope, Aspect, Curvature" tool as shown in the two ...
- 2,002
5
votes
Hydrological Enforcement of culverts in QGIS
I am in doubt this plugins have the clear cut answer for you. but for this kind of analysis there are three plugins which can be useful if you like to tamper.
Prerequisites
To open these plugins you ...
- 694
4
votes
Accepted
How to calculate the impact and extent of damage of a potential tailings dam breach with ArcGIS?
There are quite a number of steps and additional data that you'd require before you can answer this question with a level of detail that is appropriate for such an important question. This is not just ...
- 56
4
votes
Watershed Tool Straight Edge Problem
Watershed straight edge is usually clear indication of processing extent being not large enough. I guess that dams extent affected result shown.
Output of watershed tool http://resources.arcgis.com/...
- 22.4k
4
votes
Accepted
Identifying highs on DEM using ArcGIS Spatial Analyst?
What I found worked best incorporated all of the answers so I thought I'd add it here rather than accept just one of them.
I used the 'peak' tool suggested by Hornbydd to create points at each peak, ...
- 1,876
4
votes
Accepted
Calculating Flooded area / Inundation in ArcGIS for Desktop?
Your workflow should get you what you need.
I'd recommend to use Con for the first two steps (then you can aggregate them into only one step).
I don't know of any existing tool that does these ...
- 4,920
4
votes
Calculating average stream slope at each location along stream using ArcGIS Desktop?
I would say your problem is a network searching problem. You need to identify the source for every point on the network, it's distance and the elevations at the source and at point on network. Once ...
- 41.8k
4
votes
Accepted
Issue with r.watershed run by QGIS-Python-processing.runalg
Using the following code worked for me:
from PyQt4.QtCore import *
import processing
# "mydem" is the loaded dem layer
dem=QgsMapLayerRegistry.instance().mapLayersByName("mydem")[0]
fileName = dem....
- 74.6k
4
votes
Locate wet patches using DEM
The subject has a lot of atention among specialists and the number of tools available depends on the amount of work you wnat to put on it. The paradox is that you want to avoid wet areas while ...
- 3,160
4
votes
Accepted
Assigning land cover type (in shapefile) to hydrologic soil shapefile in QGIS?
I think I understand what you are looking for. You are needing to assign the Soil Type to a Specific Landcover, within a larger watershed.
This is a pretty straight forward task using the "Intersect"...
- 3,637
4
votes
Watersheds in SAGA Fill Sinks Wang & Liu tool
If you look closely at the tool documentation, there's some references info . The problem is that the text needs to be bought or to have some student account access.
Wang, L. & H. Liu (2006): ...
- 7,728
4
votes
Accepted
Forming continuous network out of discontinuous lines in ArcMap
You were on a right path with collapsing lines. Almost, because it won't handle complex polygons. So, merge streams and polygon outlines into single feature class and dissolve (no multipart) to get ...
- 22.4k
4
votes
Drainage divide
So I solved my problem,
I classified the flow direction raster into 2 directions(EAST and WEST) then using the basin shapefile did majority analysis for the flow direction raster.
I end up with a East ...
3
votes
Identifying highs on DEM using ArcGIS Spatial Analyst?
You should always search Arcscripts website as there are many user community tools already written.
A quick search of the word "peak" threw up the Spatial Analyst Supplemental Tools.
- 41.8k
3
votes
How do I find out the sea levels?
Your main question title indicates you're looking at sea level and coastal areas. But we'll start at the bottom of your question and work backward.
Consider lakes and rivers. Many of them may be ...
- 15.6k
3
votes
Evapotranspiration in Modis
The first document that you should read is MOD16_global_evapotranspiration_description.pdf where is pointed out that the MOD16 global evapotranspiration (ET)/ latent heat flux (LE)/ potential ET (PET)/...
- 28.6k
3
votes
Mapping UK river gauges / stations
Depending on what you need the data for, the following links may or may not be helpful.
You may find useful data from the National River Flow Archive (NRFA), part of the Centre for Ecology & ...
- 1,203
Only top scored, non community-wiki answers of a minimum length are eligible