Latest Contributions by MarkBoucher

If you are working with the data over the network, you will get much less performance than if you work with the data on you local drive. ... View more

Add the Arc Hydro Tool Bar. ApUtilities is near the right end of the bar. ... View more

Within the district scale site there is a large, flat area where water collects (this urban district is surrounded by levees, so water flows and collects in this specific area). This is my specific area of study. Flat areas don't model well. Hilly areas do. If I were you I would determine where the water will "leave" the leveed areas (where a pump or gate will be or currently exist). I would then create a an agreestream layer and "breach" the levee at this location with a short line. This is likely the low point behind the levee. Then, I would copy the storm drain or channel system into the agreestream layer. You wouldn't need to delineate well defined drainages in the DEM, but may need to "breach" bridges or culverts at road crossings. Then, make sure the DEM is well defined to its edge and add lines in the agreestream layers where the DEM poorly represents reality. To make the resulting fil raster "hydrologically correct" you may need to put in an "innerwalls" layer. Use this to input polylines where you know there are subwatershed boundaries in the DEM. These could be RR tracks, property lines that you know overland flow would not pass. If you do the above, when you process the DEM by burning the streams, building walls, and filling the sinks, you will get a hydrologically correct fil raster that will result in a flow direction (fdr) grid that is meaningful for the rest of your analysis. You will want to use the levee "breach" locations as hydrology points. PS - I've found that if the agreestream and innnerwalls layers are in a gdb, the number of errors are reduced. ... View more

Spatial Analyst>Hydrology tools are able to create a stream order. They start with a stream raster AND you need a flow direction grid. So, if all you have is polylines of streams, you will need to make a raster with them. This should be an easy polyline to raster function. Once you have the stream raster, run stream order tool to get another raster that depicts the stream order. Then you need to convert the stream to a feature to get back in to vector data where you can symbolize the streams based on the stream order (grid code in resulting polyline feature class). If you don't have a flow direction grid, or need to make sure you have one that exactly matches your stream polylines, you can burn the flow direction of the streams into a raster using Arc Hydro Toolbar>Terrain Processing>Flow Direction with Streams. I believe the direction of the polyline is key to making this work right. To check the direction of the polylines, change the symbology to show arrows on the lines. The arrows will point in a direction based on the direction the polylines are drawn. There is a tool to called Flip Line under Editing tools that allows you to flip the lines that don't point in the right direction. Also, see this recent thread: http://forums.arcgis.com/threads/75629-Redrawing-rivers-in-proportion-to-their-discharge?highlight=stream+order ... View more

Here's a good article: http://blogs.esri.com/esri/arcgis/2008/05/03/u-s-hydro-flow-lines/ Also related this tool in Spatial Analyst:  Spatial Analyst Tools.tbx\Hydrology\Stream Order http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z00000057000000.htm Use the tool to create the stream order and then use Quantities/proportional symbology. Good Luck! PS - This results in a raster. You then have to convert the stream raster to a feature to get the polylines that have a grid code based on the stream order. Use proportional symbology based on the grid code. ... View more

Sounds like you want to treat the center of each grid like a point and compare it to the surrounding grids. I looked around and found the Data Management Tools.tbx\Projections and Transformations\Raster\Shift tool. With this you can shift your dem over in the x and y directions to get four shifted dems. For example, you create a dem that is shifted one grid size "down" (south 10 feet in my case). Then you can do "minus" raster math between each of them. The resulting raster is the vertical elevation between the dem cell and one cell north. Repeat this logic for the other directions to make a total of four difference rasters. Then perform "divide" using raster math to get the slope in each direction. Some trig raster math will give you the angle of the slope (inverse tangent?). Does that make sense? I threw together a model that calculates the four slopes based on my logic. [ATTACH=CONFIG]20978[/ATTACH] ... View more

It could be I don't quite understand what you're trying to achieve. I think what you are wanting is the slope of each grid in the E/W direction and the N/S direction. When you create the aspect from the dem, you get at grid of the direction of the slope. The value in that grid is the aspect in degrees (North being 0 and 360 I believe). The slope tool creates a grid with the slope for each cell. I assume the down slope is in the same direction as the aspect direction. Using the sin(aspect)*slope I think will give you component in the East/West direction. The cos(aspect)*slope should give you the component int he N/S direction. Steps I'd try: Run Spatial Analyst Tools.tbx\Surface\Aspect tool: Output = "aspect" grid Run Spatial Analyst Tools.tbx\Surface\Slope tool: Output = "slope" grid (choose degrees or % slope options for output). Using either Spatial Analyst Tools.tbx\Math tools and Spatial Analyst Tools.tbx\Math\Trigonometric tools to perform the trig and math functions: EWslope grid = sin(aspect)*slope  and then separately NSslope grid = cos(aspect)*slope You would end up with two grids. Simply using the tools you would have several steps. These could be set up in Model Builder to run. In the Raster Calculator, you  you could get by with two runs. Maybe I'm misunderstanding your goal and someone else can better explain. Cheers. ... View more

The slope would be downhill in the direction of the aspect, I'd think. So, how about trying sin(aspect)*slope for one direction and cos(aspect)*slope for the other? I'm not sure what to do if the cell is perfectly flat like the top of the hill of bottom of a sink. Should be a rare occurrence. ... View more

There is a the slope command in Spatial Analyst and you get the vertical angle with the horizontal plain using that. The aspect command gives you the 360 deg horizontal direction of the slope. The default symbology is the N, NE, E, SE, S, SW, W, NW directions, but the raster values are down to the sub degree precision. Maybe a combination of these two would work. In Spatial Analyst hydrology the flow direction command gives you a number representing one of the 8 directions (N, NE, E, SE, S, SW, W, NW) that is unique to the four corners. This is slope is towards the lowest of the of the surrounding cells and may not be the same as aspect. Hillshade produces a value based on horizontal direction, but I'm sure if it can be correlated to cardinal directions. Just some ideas... ... View more

I would look at the fil raster and see if the creek is discernible in it. Apply the same color ramp to the fil raster as you do to the rawdem raster. The fil raster is what is fed into the flow direction tool and that in turn defines the stream raster and eventually the stream network. If the streams are not discernible in the fil raster, then there is likely a need to change the rawdem prior to filling by burning in the streams in some locations. For example, a bridge crossing (or slight anomaly in the raster) may cause the creek in rawdem to fill and then the flow direction will not follow the creek, but will go around the bridge. In this case, you need to "burn" a line across the bridge to cause the eventual flow direction to follow the creek through the bridge. Also, there are also times with the rawdem is so flat that it is not well defined. In these cases and the flow direction will cross what is actually a watershed boundary. To deal with this once can build a "wall" in the dem so the flow direction will come out "hydrologically correct". I use the ArcHydro tools for my hydrology analysis. This has tools for burning in streams and building walls. ... View more

Other's also having problems posted elsewhere. http://forums.arcgis.com/forums/120-Hydro ... View more

Could one do this by interpolating first and then clipping the results? or would the lack of a barrier skew the results? ... View more

If you have Spatial Analyst (SA), there is a tool called raster calculator. You can add it to the SA toolbar and then use it to perform basic raster math such as multiplying a raster by a constant, adding rasters together, preforming if/then functionality on rasters. Model Builder is included in ArcMap and can be used to put together visual "macro". That is, you can drag and drop data from your mxd and tools from the toolbox into a model. Then, like a flow chart, you can connect them, change settings in the tools, define where you want the output to be saved, and run the model. In multi-step processes it works to both document the process and revise the process if at first you don't succeed. Hope this helps. ... View more