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Questions tagged [flow-direction]

In hydrological modelling, flow direction shows the side the flow goes towards. Flow direction is used in spatial analysis to generate a drainage network by generating flow accumulation.

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Setting boundary condition for urban catchment flow direction operation

I am trying to delineate individual catchments for a large number of kerb inlet pits from a LiDAR DEM using open source tools (QGIS, WhiteBox). In areas where the LiDAR has sampled verge elevations to ...
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New flow direction attribute for sub-catchment layer in QGIS

I have a polygon layer in QGIS with self-created sub-catchments. I also have a DEM, a flow-direction raster and a raster with the corresponding stream network and stream order. I would like to create ...
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Channel network from DEM of a river has unusual linear lines

So I needed to obtain channel network, basins, flow direction, etc. I downloaded aster_DEM from usgs, clipped it to an extent, warped it to UTM projection, then filled the sinks using Wang and Liu ...
SHAISHAV ACHARYA's user avatar
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QGIS: determining the ice divide on a small ice cap

I have a GeoTIFF file with the surface elevation of a small ice cap. The ice cap has an ice divide, where the ice diverges. Part of it flows towards a glacier in the north, the other part flows ...
user236934's user avatar
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Running grass7:r.watershed in QGIS gives different results to running identical process in QGIS

a former colleague created a QGIS tool in Python for the Team which creates Flow Routes and TWI (Topographic Wetness Indicator) maps for a selected location. I have run through the code and copied the ...
sar_copp's user avatar
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How to set up r.watersheds if it generates too short streams on river valley sections that are too wide

Related to this question too I am delineating a very big watershed with very wide river valley. When I tried to perform with PCRaster, the directions map wasn't generated properly, as sticks upon ...
Nikolay Yasinskiy's user avatar
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129 views

Exporting ldd raster from grass to PCRaster fails

I successfully exported Float32 SCALAR data with r.out.gdal input=$file output=$file.map format=PCRaster type=Float32 createopt="PCRASTER_VALUESCALE=VS_SCALAR" but for ldd data (previously ...
Nikolay Yasinskiy's user avatar
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520 views

How to measure the distance between two points in the same layer accounting for stream meandering in ArcGIS Pro

I am trying to measure the distance (in meters) between points that are in the same layer and I would like to account for the distance of meanders in the stream if possible. I was able to calculate ...
Rnchriz's user avatar
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Flow direction outputs (ArcGIS Pro: Hydrology Tools) returning 255 values rather than 8 (D8 settings)

I am working with 10-meter resolution digital elevation models to produce flow direction raster images to be used ultimately for the watershed tool in ArcGIS Pro. When I use one DEM at a time, things ...
Kurtis_Fisher's user avatar
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Measure flowpath length from a point

I am using QGIS 3.28.2-Firenze. I have am using WBT "tracedownslopeflowpaths" to establish flowpath from a 3D scalar point (numbered points in image). How do I set a measured distance (1320 ...
Michael Leonard's user avatar
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Tool for modelling uniform groundwater flow from points and isopotential lines (elevation contours) - QGIS

I am going to investigate where a specific particle in a groundwater system will be found in 10 years. I have the following data: A vector point layer with x and y coordinates of points I want to ...
T_QGIS_ENV's user avatar
3 votes
1 answer
157 views

Adjusting flow direction of river based on DEM in QGIS

I have a huge vector layer as a line, that represents the river. The problem is that the flow direction is sometimes wrong (goes uphill). But I can't correct that manually, cause the layer is too big. ...
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Display line with color gradient (or fade effect) based on the value of the vertices it connects

I have two vertices connected by two lines (we can assume way out and way back from point A to point B). In the picture I represented the lines with two arrows curved by adding a midpoint and its ...
Michele Cordini's user avatar
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How to determine North-facing, south, east and west forest edges in QGIS

I am using QGIS. I have a shapefile with 41 polygons representing forest patches. I want to assess the effect the forest edge direction has on vegetation within the forest patches. I have defined ...
Donald 's user avatar
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318 views

Why some flow direction cell of GRASS r.watershed have no data value?

Using r.watershed inside QGIS, I am getting no data value along some streams for flow direction. I tried the r.fill.dir and for the same raster it does not give any no data value for the same cells (...
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Flow Direction flowing opposite to actual direction

I am using ArcMap 10.7.1. I am trying to delineate multiple urban watersheds in GIS for the City of Denver (sometimes called sewersheds) using Spatial Analyst. I am looking at several drainage points ...
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Working with the FlowDir in the national hydography dataset

In the National Hydrography Dataset there's a FlowDir field. According to https://www.townofnewipswich.org/sites/g/files/vyhlif4766/f/uploads/dataset_dictionary.pdf the two possible values for FlowDir ...
neubert's user avatar
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Preventing diagonal flow direction in ArcGIS Desktop

I would like to prevent diagonal flow direction/accumulation, as it leads to frequent "river shortcuts". As shown on the picture, instead of following the river in blue, because of the ...
Antoine T's user avatar
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104 views

Incorrect creation of flow direction raster from interpolated DTM in ArcGIS

I have DTM for quite small area (400x200 meters) which was interpolated from elevation points. I want to create raster which will show water stream (not arrows but basically slope and river flow map - ...
daky's user avatar
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Why does the Flow Direction tool output a raster with only one value?

I have a DEM with values that range from 0 to 1040. I'd like to create a layer with the flow directions by means of the Flow Direction tool in the Hydrology section of the ArcToolbox. However, when I ...
Max Muller's user avatar
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506 views

Create a flow vector NetCDF from X and Y velocity components

I want to create a flow vector NetCDF data from two .tif raster, one representing X-velocity and another representing Y-velocity component. Both raster groups have identical spatial extent. I have ...
Brian's user avatar
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Why am I getting a straight flow path (stream) in obviously varying terrain -QGIS

Does anyone have suggestions on why the streams are sometimes represented as longer straight lines, even though the hillshade and contours generated from the same DTM (filled) clearly indicate that ...
BruceT's user avatar
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2 answers
506 views

Flow Direction tool outputs strange raster that doesn't work with subsequent hydrology tools

My main goal here is to end up with a shapefile that simply defines the ridgeline in a given area. I followed the directions at How To: Identify ridgelines from a DEM and am having some trouble. ...
Nic Hertzler's user avatar
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1 answer
553 views

Calculating distance between points following flow direction on ArcMap?

I delineated flow directions in a watershed on ArcMap (10m DEM). Then I want to calculate distance between two points 'following' the flow direction in each raster cell, not a straight line distance. ...
Sumi's user avatar
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290 views

Howerive vector stream network from a DEM using D-Infinity Flow Direction algorithm?

I have been working with a 1m LiDAR derived DEM to create a vector stream network. Using the D8 flow direction, D8 flow accumulation, and a specified threshold, I was able to create a vector stream ...
sbhadra's user avatar
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1 answer
562 views

Understanding ArcGIS Flow Direction pixel values?

The range of values in my flow direction raster is 1-129. D8 method was used. I would expect 128 to be the largest value in accordance with the documentation what's more I show values OTHER THAN 1,...
Zipper1365's user avatar
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1 answer
86 views

-32768 in flow direction values of Grass GIS

I was checking the values of a flow direction tiff created with Grass GIS and the values were: -32768, -4, -3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8. This answer explains clearly the meaning of the values ...
Argent's user avatar
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1 vote
2 answers
137 views

Why do we need to make correction manually in flow direction files

I have created flow direction and flow accumulation files for my DEM. Using the feature to point function, Ive got all the points in point form and then I converted them to arrows. But most of the ...
lsr729's user avatar
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9 votes
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Displaying direction of water system with arrows in QGIS?

I would like to put direction arrows next to my Water system just like in OpenTopoMap (see the image under). I already watched the source code but they made it with Mapnik. However, I am working on ...
Svhooren's user avatar
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1 answer
354 views

ArcGIS - Flow directions in the 4 cardinal directions only (North, East, South and West)

I would like to know if there is a way to calculate the flow directions in the 4 cardinal directions only (North, East, South and West). Indeed, ArcGIS transfers the flows in the 8 directions, which I ...
Raphaël's user avatar
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0 answers
2k views

Displaying flow direction using arrow in ArcGIS Desktop?

I created a flow direction raster out of a DEM using ArcGIS Spatial Analyst Tools/ Hydrology, so the directions are coded in raster values as displayed below. [http://desktop.arcgis.com/de/arcmap/10....
Maja Ott's user avatar
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1 answer
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Are there any continental-scale flow accumulation products besides Hydrosheds?

I am trying to compute branching angles of drainage networks for roughly the western half of the U.S. Because many of these streams are non-perennial (don't have water all year), some of the standard ...
Jon's user avatar
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7 votes
2 answers
2k views

Compute flow accumulation only from flow direction?

I am looking to calculate flow accumulation from a flow direction raster. In ArcGIS there is Flow Accumulation (http://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-analyst-toolbox/flow-accumulation....
Guido A. Herrera's user avatar
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629 views

Understanding Slope Line and Flow Direction in ArcGIS Desktop?

I would like to create a Flow Direction (Polyline - not raster) which needs to follow slope direction (as arrow in picture I attached) I'm working in mike urban (SWMM Model) and the software assign ...
Tiziana Venditto's user avatar
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1 answer
219 views

Verifying an answer in a GIS book (D8 flow direction)

I am currently reading this book and I found the answer a bit confusing. Would be nice if someone could elaborate on the accuracy of the following sentence: The values 64 and 16 have the highest ...
Tsarevna O.'s user avatar
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0 answers
457 views

Getting errors after about 30 mins of processing Flow Direction using ArcGIS Desktop?

I'm trying to process the flow direction from a filled DEM using ArcGIS 10.2.2 and I get these errors after about 30 mins of processing, every time, no matter what I try. I tried changing the raster's ...
Nahas's user avatar
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1 vote
3 answers
2k views

Doing watershed delineation properly using ArcGIS Desktop?

I am using ArcGIS Desktop 10.2. I have the contours and the stream in AutoCAD Civil, after converting to a shapefile, I exported them in GIS, after I created the TIN from the contours below: ...
Anida's user avatar
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4 votes
1 answer
1k views

What is the difference between Aspect and Flow Direction tools?

There are two seemingly identical Spatial Analysis tools: (1) Surface -> Aspect: Derives aspect from a raster surface. The aspect identifies the downslope direction of the maximum rate of change ...
Sparkler's user avatar
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1 answer
118 views

Flow direction without DEM / raster

I am trying to figure out flow direction for a stream network and I do not have a high resolution DEM data for the same. I only have information about the stream orders and the network itself. Is ...
Sidhha's user avatar
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1 vote
1 answer
233 views

Create a flow network from a flow direction ARC GIS

First, I created a flow_direction from a DEM, then I applied corrections to this flow direction. Now my question, how to create a flow network (order flow) from a flow direction, that I already ...
tazrart's user avatar
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5 votes
2 answers
2k views

Flow Direction Raster Value Range

I am interested to know why ‘Flow Direction Raster’, derived from ‘Filled DEM’, generates values ranges from 1-128, with pixel depth of 8 bit unsigned integer which is readily capable to store values ...
Dave's user avatar
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1 vote
2 answers
706 views

flow direction and flow length in arcmap

I am trying to replicate a flow length calculation in arcmap 10.2. I have an elevation raster with a pixel range from 0 to 3038.96m (32 bit). When I run the flow direction calculation, the pixel range ...
nso921's user avatar
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3 votes
0 answers
1k views

Problem with Flow Direction in DEM [closed]

I have the following problem with Flow Direction Tool in my DEM and with such wrong calculated flow direction in the centre of DEM I am unable to delineate any watershed. What can I do?
Iffi's user avatar
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3 votes
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575 views

ArcGIS - Flow Direction (Algorithm) [closed]

I am curious about the algorithm of Flow Direction in ArcGIS. Recently I am studying about Hidrology, and I have some questions regard to Flow Direction in GIS. The size of this cell is 100m x 100m, ...
Jihyun Kim's user avatar
5 votes
1 answer
2k views

Flow direction generated for river is incorrect

I am trying to generate a hydrologic model and I can not really proceed on the next processes. I have this problem on generating flow direction. I have already executed fill sinks and the next is flow ...
vklopt's user avatar
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