Latest Contributions by MarkBoucher

You could use raster calculator to multiply each raster by a value and then mosaic the resulting rasters together. If this was a repeatable task, you can set up a Model Builder model to do this. ... View more

Are the rasters to be overlaid (all cover same area) or pieced together side by side? ... View more

Check http://forums.esri.com/Thread.asp?c=93&f=995&t=98735. Might be some answers there. ... View more

Try this:  Go to Customize/ArcMap Options/Raster and change the maximum number of unique values to render from the default 65536 to (for example) 10000000. In my work with Arc Hydro, this seemed to eliminate errors due to grid size. I'm not sure if there is a maximum number and I'm not sure if making the number high reduces speed for smaller projects. I hope this may help. ... View more

If your DEM grids are small/fine enough to distinguish the flatter bottom and floodplain from the banks, and you have a polyline defining the stream/river, it seems you would be able to create a slope raster from the DEM, buffer the stream and use the buffer to extract the slope around the stream/river and determine a slope that would distinguish the banks from the stream/river bed. Then you could use the Con() function to ID the grids with slopes w/in a certain range or above a certain value and this would ID the banks. ... View more

Stuart, You are right that the HEC download does not provide for 10.1 version. I'm a 10.0 user for now so hadn't noticed that. For the other versions, at least for 10.0, Arc Hydro, APFramework, etc. are all part of the installation package. Mark ... View more

If you are looking for a version of Arc Hydro, you don't have to get it from the ESRI ftp. You can go to the Corps of Engineer's software download pages and download HEC-GeoHMS or HEC-GeoRAS and get the version of Arc Hydro that works with your version of Arc Map. http://www.hec.usace.army.mil/software/ ... View more

I think there is a problem with their server. btw: Password is river.1114 ... View more

Arnauld, I assume you want the flows to follow a drainage network because you say, "I just want to join the input points to the outlet by the shortest drainage network." There are tools in Arc Hydro for doing this. You need Spatial Analyst to use Arc Hydro. If you install the correct version of HEC-GeoHMS for your version of Arc Map, you will also install the correct version of Arc Hydro. Both are free. If you haven't used Arc Hydro, it can take some time to understand it. I've written a post here (http://forums.arcgis.com/threads/53316-Why-can-t-I-define-a-stream-network) that summarizes the steps I use. There are other posts in the forums that could also help you become familiar with Arc Hydro. One is a thread I started to post solutions in one place : http://forums.arcgis.com/threads/48100-ArcHydro-Problem-Solvers. As for a drainage network, if you have a polyline dataset of the existing pipe network and also polylines at bridges (where the DEM might rise higher than the creek), Arc Hydro can "burn" these into to the DEM (lower it where these polylines are). You can use a stream (creeks/rivers/streams) polyline dataset, but I usually don't use all the lines in the stream layer because they don't always follow the terrain as well as the DEM. An intersect of the stream layer and roads can help me find bridge/culvert crossings. In flat areas, however, you may need to do a lot of "training" for the flow paths to be defined correctly and in those cases the stream layer might be best to use. In the process you will create a flow direction grid (fdr). The fdr is the basis for the rest of the processing in Arc Hydro. You may not need to go any further in the Arc Hydro processing steps for what you want. Using the fdr and the Arc Hydro flow path tracing tool in the Arc Hydro toolbar you can get traces of the flow paths from points you click in the watershed to the outlet.  If the fdr is correct, the traces will be the lines that join the "input points to the outlet by the shortest drainage network".  You could then convert those lines to features using a menu command in the Draw tool bar. Hope this helps. Mark ... View more

Are you doing this regardless of the topography? ... View more

Caterina, You need to make a hydrologically correct DEM and then create a flow direction grid. After that there are tools for finding what you want. You will need Spatial Analyst. Arc Hydro (loads with installation of HEC-GeoRAS) has the tools for this, but there are some tools under the Spatial Analyst Tools.tbx\Hydrology.  Maybe the Spatial Analyst Tools.tbx\Hydrology\Flow Length tool would give you what you want. If you need the trace or length to stop a the drainage network, and you have the drainage network in a polyline format, you can use those polylines to set the direction of the flow direction grid to 255. I believe this will "stop" the distances at the drainage network. I think 255 is  the number for a "sink". I created this post to "collect" comments on Arc Hydro. http://forums.arcgis.com/threads/48100-ArcHydro-Problem-Solvers This post can be found there and has details for the Arc Hydro process. You probably don't need to go past the flow direction step. http://forums.arcgis.com/threads/53316-Why-can-t-I-define-a-stream-network Mark ... View more

Joe, What do you mean by, "the maximum value in each basin"? Do you mean the max value for the flow accumulation grid (fac)? The max value fac for each basin will be at the coast. Not all of the grids will flow to a stream that flows to the coast. I would think that you will have many very small watersheds, possibly several that are one grid in size, that drain to the ocean. So, in theory, every grid that boarders the ocean will be a point of interest for you. If you can isolate the grid cells in the fac that boarder the ocean, you can convert them to points using tools. Then you could filter them based on some minimum fac value. Then you can add lat & long fields to them and calculate geometry for the lat & long. ... View more

I assume you've seen http://forums.arcgis.com/threads/72067-ArcHydro-1.4-HEC-GeoHMS-HEC-GeoRAS-compatibility. ... View more

My understanding from my GeoHMS training via ESRI is that ESRI is the developer of both. The Corps (HEC - Hydraulic Engineering Center http://www.hec.usace.army.mil/) hired ESRI to develop HEC-GeoHMS and HEC-GeoRAS. At times, I understand (and I could be off here) there can be a lag between the latest ArcHydro (ESRI controlled release) and HEC-GeoHMS (Corps controlled release). This is because HEC staff does a thorough review of the product before they release it internally. This could explain why it takes a while for a versions of the HEC products to catch up with a new version of ArcMap. My understanding (and I could be off here too) is the the Corp uses and supports the HEC products in-house. They do not provide software support to general public (their documentation is usually darned good and suffices for my purposes). That is why there are companies/consultants that provide training on the HEC products instead of HEC itself. The HEC products are posted on-line because they are government funded and therefore public domain. Again. This is just my understanding of the situation. ... View more

There is a way to increase the size of a raster ArcMap will deal with. This post describes the "AdvancedArcMapSettings.exe" registry editor to use to do that. http://forums.arcgis.com/threads/48666-ArcHydro-doesn-t-output-to-shapefile?p=203314#poststop Also, I found under the menu "Customize>ArcMap Options>Raster Tab>Raster Dataset subtab - Max Number of Unique Values to Render" has the same number I put into the "AdvancedArcMapSettings.exe" interface. As a matter of fact, it appears to be the same variable and either interface changes the same value. Maybe increasing this value will allow you to process a larger raster. ... View more