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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 ...
Richard's user avatar
  • 1,831
10 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 ...
Micha's user avatar
  • 15.7k
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( $...
Bera's user avatar
  • 74.8k
9 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 ...
Tom's user avatar
  • 4,138
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 ...
Hornbydd's user avatar
  • 43.8k
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 ...
WhiteboxDev's user avatar
  • 11.1k
5 votes
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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, ...
Soalpa's user avatar
  • 193
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 ...
wanderzen's user avatar
  • 2,140
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 ...
Uditha Herath's user avatar
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 ...
Phophos's user avatar
  • 56
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 ...
Marco's user avatar
  • 3,240
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"...
Keagan Allan's user avatar
  • 3,756
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): ...
gisnside's user avatar
  • 7,858
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 ...
FelixIP's user avatar
  • 23.2k
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 ...
Abdullah Nagy's user avatar
3 votes

How to Create a Catchment Area of a Polygon (Wetland) using DEM in QGIS or Whitebox GAT

If you have a vector polygon representing a wetland, then in Whitebox GAT, you just need to convert that polygon to a raster using the Vector Polygons to Raster tool. Use the DEM as the 'Base Raster ...
WhiteboxDev's user avatar
  • 11.1k
3 votes
Accepted

Calculating flowaccumulation in specific areas

Using a weight grid in the flow accumulation procedure should get you there. Use the raster calculator (or the Con or reclassify tools) to create a weight raster where the yellow zone equals 1 and ...
Jae's user avatar
  • 1,302
3 votes

Negative values in r.watershed flow accumulation

It was solved long ago in the comments, but better as an answer. Quoting the manual of r.watershed: Negative numbers indicate that those cells possibly have surface runoff from outside of the ...
Marco's user avatar
  • 3,240
3 votes

HEC GeoHMS generates wrong catchment area

I beleive the problem is with ArcGIS "HEC-GeoHMS uses ArcGIS and the Spatial Analyst extension to develop a number of hydrologic modeling inputs for the Hydrologic Engineering Center's Hydrologic ...
Jakub Sisak GeoGraphics's user avatar
3 votes

Creating water surface from vector line in QGIS

I think @TimCouwelier’s comments are on the right track. I used GRASS GIS r.plane to create a raster plane with a given dip (inclination), aspect (azimuth) and one point. You need to provide a list of ...
MarcM's user avatar
  • 1,156
3 votes

Incorrect length from Flow Length tool

You already figured out your problem. The unit of measure is in degrees, therefore your raster is a measure of flow length in degrees. Before doing your analysis, you need to use the Project tool ...
mmoore's user avatar
  • 1,011
3 votes
Accepted

How to display Flow Direction arrows + Burn Stream Netwok in QGIS?

Regarding your first question (it's usually better to focus on one question per post): In GRASS you can display vectors with direction arrows. In the gui there's a checkbox "Display direction of ...
Micha's user avatar
  • 15.7k
3 votes
Accepted

Obtaining length of river upstream of points up to next point using ArcGIS Desktop?

RivEX does much if not all of what you are asking. For computing upstream length you would run the appropriate RivEX attribution tool to encode that into the network then transfer the lengths to your ...
Hornbydd's user avatar
  • 43.8k
3 votes
Accepted

Selecting contour lines with higher elevations on either side

To find depressions and peaks on a surface, assuming you have the DEM that created the contours: The first step is to fill (see Are there any open source tools to detect and fill sinks on a DEM?) the ...
Michael Stimson's user avatar
3 votes
Accepted

Generate Height Above the Nearest Drainage (HAND) using QGIS

Actually, I did not generate HAND from DEM before, but based on High Resolution Hydrography and Hydrologic Modeling PDF reference file, they use TauDEM tool accessed from ArcGIS, as you can see in ...
ahmadhanb's user avatar
  • 41.1k
3 votes
Accepted

QGIS: Saga Channel network: how to prepare SRTM data

You might want to try running Fill Sinks. This is available using SAGA via Processing. There may be GRASS versions too. I didn't see any mention of it in the tutorial you linked to, so it's worth a ...
Steven Kay's user avatar
  • 20.5k
3 votes

Longest Flow Path in QGis

After a long and painful process, I found a way to do it combining GRASS GIS and QGIS with GRASS. Here is how I did it: In QGIS load the DEM raster. Using GRASS for QGIS run the r.watershed command (...
rsuarez1's user avatar
3 votes

Limiting flow direction to D4 instead of using D8 in ArcMap?

Let me know if this is what you expecting to see: I'll post workflow.
FelixIP's user avatar
  • 23.2k
3 votes

Hydrological conditioning using stream vector in GRASS?

Please check r.carve which generates stream channels by taking a vector stream map, transforms it to raster model and subtracts depth from a DEM writing out a new, modified DEM.
markusN's user avatar
  • 13k
3 votes
Accepted

Calculate Polygon Centerline with a LeastCostPath approach

I have spent many hours working on similar problems. I published a paper about it, even. In the Matlab toolbox presented there, I use the shortest path just like you're doing. In my experience, there ...
Jon's user avatar
  • 2,894

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