Questions tagged [topographic-wetness-index]

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Generate topographical index from a digital surface model (DSM) to generate a flood susceptibility map [closed]

I'm performing a random forest model to generate a flood susceptibility map, I have LiDAR data from the study area where I generated Digital Surface Model (DSM) and Digital Terrain Model (DTM) raster ...
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1 vote
0 answers
134 views

QGIS Flow accumulation tool frozen at 100%

My goal is to apply a topographic wetness index to a DEM using QGIS Version 3.20.2-Odense, running on a macOS laptop. I have clipped my DEM layer for the appropriate study area, and calculated slope ...
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1 vote
1 answer
116 views

Reproducing terrain ruggedness index from the original paper example [closed]

I am not able to reproduce the terrain ruggedness index for the example used in the original Riley et. al paper. The example is as follows: When I try to reproduce the numbers in MS Excel I get ...
2 votes
1 answer
104 views

Unexpected error while RSAGA raster calculations

I want to use RSAGA package in R to calculate the topographical wetness index. However, while applying the rsaga.wetness.index() function, R gives me an error message (see below). My question is, ...
0 votes
0 answers
141 views

Topographic Wetness Index difference between SAGA and TauDEM

I calculated Topographic Wetness Index (TWI) using SAGA and TauDEM. Overall trend is similar but SAGA returned larger values compared with TauDEM. Sometimes the deviations are as large as 7 or 8. I am ...
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1 vote
0 answers
55 views

NoData values in soil wetness index

I would like to know why I am getting no data pixels in my soil wetness raster, since none of the source rasters used to calculate the SWI have no data values. method I used: soil data from HWSD FAO ...
  • 33
0 votes
2 answers
60 views

Getting error 000539 when calculating TWI?

I'm trying to calculate the twi from my area using LN((flowaccu+1)*900/Tan(sloperadian). My first result was wrong because my area is an endhoreic basin. So I made a flow accumulation raster based on ...
  • 33
6 votes
1 answer
388 views

Choosing Topographic Wetness Index or Flow Accumulation raster?

What is the better raster to use qualitatively - Topographic Wetness Index or Flow Accumulation - to clearly see potential areas of surface flow/wetness across a landscape? As an example, what's "...
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6 votes
1 answer
1k views

Choosing parameters for SAGA Wetness Index?

I've been working with SAGA GIS to calculate the Topographic Wetness Index of an alpine catchment. I am using the tool Terrain analysis > Hydrology > SAGA Wetness Index because, compared to ...
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2 votes
0 answers
419 views

Using SAGA-GIS topographic wetness index in R?

I want to create a topographic wetness index (TWI) in R and I am trying to set an environment according to the help of RSAGA-package but I am always facing with an error appears in a different term. ...
  • 303
6 votes
1 answer
913 views

Strange output from RSAGA topographic wetness index? [duplicate]

I am trying to generate a topographic wetness index raster with the RSAGA package in R. The output I am able to generate does not make sense to me, as it has a large number of NA cells and I wonder if ...
  • 309
1 vote
0 answers
111 views

Hydrology Analysis via SAGA - what is the unit? [closed]

I did a couple of analysis via SAGA about an area in Iceland...I've never worked with SAGA before, could anyone tell me what Units the numbers in the legends for "Catchment Area Recursive" and "...
  • 19
11 votes
2 answers
562 views

Cleaning blocks pattern from urban LIDAR (blocks uplifted from streets)

We have a 1-meter LIDAR DEM from a city. A small subset can be downloaded from this link: This screenshot shows raw DEM with gray palette (darker belts are streets, and greyish and whitish ...
  • 123
10 votes
1 answer
17k views

Calculating Topographic Wetness Index (choosing from different algorithms)

Topographic Wetness Index can be expressed as Ln(a/tanB) based on the idea of Beven and Kirkby (1979) where a is the specific catchment area (a=A/L, catchment area (A)divided by contour length(...
  • 618
7 votes
1 answer
8k views

Calculate Topographic wetness index in SAGA

i am currently working on a project which involves the quantification of the wetness in certain areas. However it produces quite different results from what i expected. I'll describe the steps i have ...
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