10

You can achieve this result with styling. Take the water line layer style and add a new symbol layer, select marker line and display it on central point Select the marker layer, select the arrow symbol (at this point you can also import another svg symbol if the default arrow doesn't suit your needs), set its color. Beside the rotation setting, click the ...


7

The following is a step-by-step process for how to take an ArcGIS D8 flow direction raster and use it to perform a D8 flow accumulation operation in Whitebox Geospatial Analysis Tools. I will preface this by saying that it would obviously be much easier if you had the original DEM from which the flow direction raster was derived. Also, I'm making the ...


6

There are eight valid output directions relating to the eight adjacent cells into which flow could travel. This approach is commonly referred to as an eight-direction (D8) flow model, the direction coding is shown: If the water will flow to the cell immediately to the right, it will be assigned a code of 1, if it flows to the top right cell then the code ...


4

The flow direction is indeed an 8 bit image, irrespective of your input (32 or 64 bit float), from the Esri help page: From the centre pixel (blue) the value indicates which way the flow will go from 1 (East) to 128 (Northeast).. From flow direction you need to proceed to Flow Accumulation or Flow Length which uses this direction raster to calculate the ...


3

It looks like your issues may in large part be caused by the large flat in the NE portion of your basin. Different pit filling and flow direction algorithms will handle this area differently, and it looks like the one you are using is forcing the flow out of your basin instead of into your expected network. First, Bill Chappell's answer provides some good ...


3

Watershed delineation is tricky, I usually include a larger area then my study area so I don't have anything weird at the edges. i.e. like the edges are cliffs or walls. With that being said, I also include a background stream layer to check that my calculated stream fits the background stream. This stream layer could be a topo map, just to confirm my data ...


2

From what I see in your tests and data results, i would say the same as you : "the only difference is that "Flow Direction" returns unique values (powers of 2) while aspect returns a continuous range of floats" I would add Flow Direction is a sort of subtool (maybe somewhere based on the aspect tool and doing exactly what you did) used to precisely ...


2

The NHD distributes all of the elevation processing products along with the stream lines and catchments (Example for PNW). Note that these products are the "hydro corrected" products that are used to build the catchments, so they should essentially match flow boundaries and flow lines that are present in the NHD+v2 catchments. It is at the native 30m ...


2

A new GRASS addon r.accumulate is available. This module only requires a flow direction map to calculate weighted flow accumulation. If you have a drainage map from r.watershed, r.accumulate direction=drain_directions accumulation=flow_accum or using its GUI, In this example, the yellow arrows and color-coded numbers show flow directions and accumulation,...


2

According to the ArcGIS Help file: If a cell has the same change in z-value in multiple directions and that cell is part of a sink, the flow direction is referred to as undefined. In such cases, the value for that cell in the output flow direction raster will be the sum of those directions. For example, if the change in z-value is the same both ...


2

My hypothesis is that you have some local minima that attract the flows (called sink). This is frequent when you start with a raw DEM. I therefore suggest that you run the fill sink function first. This should solve your problem. A sink is a cell with an undefined drainage direction; no cells surrounding it are lower. The pour point is the boundary cell ...


2

There are a number of possible reasons for this. Preparing the DEM for hydrological processing first is the key, rather than editting the results afterwards. ESRI provide a lot of information on the Hydro Tools. For instance, make sure you run the sink process to fill sinks before you do your analysis. Optionally, you can then use the fill tool to ...


1

What @Hornbydd mention is most often the case for seeing an empty (0) value raster. When you are running the tool, go to Environments -> Processing Extent. 'Default' should work in this instance or you can test out other extent options. You could also try in a fresh MXD were no settings have been set. Also confirm that there is a coordinate reference ...


1

If you follow exact steps from ESRI, it works and will produce something like that: I don't like that they are disconnected. Perhaps create sub-catchments from stream network and assume that divides between them ARE ridges: Note smaller flow accumulation threshold you'll use to derive streams will result in more detailed ridges network. Consider erasing ...


1

If you have the Spatial Analyst extension, you could use the Flow Length tool to create a flow length raster. Then calculate the difference between the flow lengths of each pair of points based on which cell of the flow length raster they coincide with. (Of course you would need to be sure that both points in the pair are on the same stream).


1

Rotate your cost raster (DEM) by 45 degrees using any point in the middle. Set env. extent and cell size to ROTATED. Derive rows and columns rasters using technique described here. Call rasters accordingly and find diagonal cells: arcpy.gp.RasterCalculator_sa('("ROWS"*1261+"COLUMNS")%2', "C:/SCRATCH/chessboard") I used 1261 ...


1

The D8 flow direction is based of work by Jenson and Domingue (1988). Based on this model any one cell has 8 possible directions of flow out of the cell. The direction of flow is determined by the elevation raster and the direction coding just indicates which of the 8 cells it will move (64 and 16). I believe that ArcGIS encoding is as follows: 1 = East 2 =...


1

I'm not sure of ways to do that without a DEM, however depending on the size of the project extent I would consider downloading a DEM from the SRTM site and running your analysis on that. The resolution will be approximately 30 meters but its better than not having a DEM


1

There are a few more steps steps you must take. Use the Flow Accumulation (Spatial Analyst > Hydrology tools) tool to create a flow accumulation grid. Create a stream network using the raster calculator tool (Spatial Analyst > Map Algebra). You should enter a funtion like: SetNull("[Flow Accumulation Grid]<[flow accumulation threshold],1) [brackets] ...


1

The very first step is Fill. It fills sinks in elevation model. Next - flow direction on filled DEM. After that you can do all other things, like flow length, using flow direction.


1

Have you considered "burning in" the main drainage channel? This is a process which is explained well in another thread here: Burning stream network into DEM layer using ArcGIS Desktop? It can help to account for common errors in elevation data (like bridges or roads crossing the river). It should force the flow in that area and produce a more accurate ...


Only top voted, non community-wiki answers of a minimum length are eligible