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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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-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 ...
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46 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 ...
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1answer
242 views

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 ...
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1answer
90 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 ...
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145 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....
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28 views

Removing loops from geometric network?

I have geometric network of a river system and I used the SET FLOW DIRECTION tool in ArcGIS 10.5 to attribute flow direction to the network. The Problem is that almost 50% of the network comes out ...
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30 views

How to divide the flow that has multiple outstreams [duplicate]

I have an incoming drain (CO-1), that is split into multiple outgoing drains ( say, CO-2 and CO-3). It goes without saying that the incoming drain has to be higher than the outgoing drains. I'm given ...
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1answer
27 views

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 ...
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2answers
271 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....
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118 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 ...
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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 ...
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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 ...
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3answers
379 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: ...
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1answer
283 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 ...
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1answer
69 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 ...
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1answer
107 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 ...
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2answers
891 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 ...
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2answers
519 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 ...
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566 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?
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0answers
478 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, ...
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1answer
1k 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 ...