Latest Contributions by MarkBoucher

Here's what I do when all else fails...  applies to any ArcGIS puzzling problems, not just Arc Hydro. http://forums.arcgis.com/threads/29202-Solving-Arc-Hydro-Problems-by-deleting-TMP-Files?p=97445#post97445 ... View more

You might check the PRISM site at Oregon State University for ready-made grids of the US. I know the PRISM methodologies are extremely complex. They use regression on several variables including distance, aspect, elevation, etc.  If there was a model in ArcGIS or if the PRISM method was explained enough to use ArcGIS tools to do something similar, that would be fantastic. The Thiessen method is well know and easy to use, but it does not take orographics into account. ... View more

Hmmm, me too. But if you click on the highlighted topic on the left, it reloads properly. Didn't think of clicking that! Works for me now. ... View more

What kind of lake data do you have? Contours? Have a look at this: http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?id=1226&pid=1221&topicname=Surface_Volume_(3D_Analyst) and this: http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?id=1283&pid=1277&topicname=Cut/Fill_(3D_Analyst) Those links give me a "Sorry, that topic cannot be found" error. ... View more

I did a quick search and the second hit I looked at looks like about what I would share with you if I had the time. Check it out. http://www.crwr.utexas.edu/gis/gishydro06/ArcHydro/UpperPearl/Exercise2/ArcHydroExercise2.htm ... View more

In moments like these, this is my first action... http://forums.arcgis.com/threads/29202-Solving-Arc-Hydro-Problems-by-deleting-TMP-Files ... View more

You could also created a field in your polygon feature class (FC) with the value you want. Then perform an intersect between the point FC and the polygon FC. The resulting point FC will have the attributes of both. If you want this value back in your original point FC, then join the intersected FC with point feature class using a unique identifier (e.g. ID) and use the field calculator to make the value in the original FC equal to the value, then unjoin the FCs. The spatial join would be simpler, but you still need to do the final step if you want to unjoin the FCs. ... View more

My first reaction is explained in my post here: http://forums.arcgis.com/threads/29202-Solving-Arc-Hydro-Problems-by-deleting-TMP-Files ... View more

I think I understand your point, Lady_Jane. Correct me if you think I'm missing it. If you put a broader range of values in the con() function, I suspect you will get a "cloud" of points that you would have to sort through thus not making the job any easier than other ways already discussed. ... View more

I tried using your idea with my project. The result was it identified only 3 points out of the more than 2 dozen that it should have. I checked one of the upstream grids cells that my method identified. That point had 11301 cells in its fac grid where I wanted to have 10890. Identifying the fac grids around it revealed that they all had less than 10890, but when they accumulated at that grid cell, the next grid cell downstream for both of them, they had 11301. So the Con() function may not locate all the points. After going through this, I almost certain that you will not be able to delineate watersheds with any specific area. You can come close, but can't do it perfectly. ... View more

pingelid, It seems like you could use the flow accumulation grid somehow to do this. I tried to look at the one I'm working on using the "unique values" symbology. I removed all the values and then tried to add values. I have a 10'x10' grid so 25 acres  = 10890 grids. I tried to add multiples of 10890, but only rarely did I see an exact multiple. It was time consuming and I could see that I wasn't going to get what I wanted early on. The USGS tool might be useful, but not if you need the results in your specific dataset on you desk top. In the Arc Hydro workflow, there is a point where, before the stream definition, you ask it to start the stream only at a certain number of cells. I set the value at 10890 (25 acres) and ran the whole Arc Hydro workflow to AdjointCatchement step. Then used the Point Delineation tool and checked. Sure enough, when I delineate a watershed at the upstream end of of the drainage lines, I get really close to 25 acres. So, this would take a while, but you could: * run the process up through stream definition and then once you have the fac grid use 25 acres, 50, 100, 125, etc. worth of grid cells to produce several str grids (str25, str50, etc) * convert the strs to lines using Conversion Tools > From Raster > Raster to Polyline. * Place (snap) batch points at the upstream ends of the stream networks (this would be much easier than stopping at the str grids and visually trying to place the points on the grid cells). * Run batch subwatershed delineation on the points. It seems it would take some patience to place the points, but you could use model builder create automate the creation of str25, str50, etc. grids and convert them to polylines.Then, after you manually place the batch points, you could do the subwatershed delineation in one operation. If there was tool to place the points a the upstream ends of the str's polylilnes automatically that would allow automation of the whole process. Maybe someone could write a script to place a point at the high value grid cells of the str grids (?). FYI - I tried this to the 25 and 50 acre level. The results were mixed. I got mostly 25 acre watersheds, did get some larger, up to 39 acres. It seems that the stream segmentation function may have some logic in it where it allows a watershed to be larger when there is a certain condition. I can see this when two small watershed branches come together and each subwatershed is smaller than the desired starting stream size, but when they come together, combined they are larger. At this point, I think it would start the stream at the confluence. Let us know what works out in the end. ... View more

For Arc Hydro errors (or any other puzzling errors) read this: http://forums.arcgis.com/threads/29202-Solving-Arc-Hydro-Problems-by-deleting-TMP-Files?p=97445#post97445 ... View more

I've had success using DSS utilities that I found via http://www.hec.usace.army.mil/software/hec-dss/hecdss-commandpromptutility-intro.htm. However, I was automating the import of rain data into DSS. For example, the DSSTS (time series) tool worked well once I understood it. I was able to create a batch and python code to do all I wanted. Maybe they have a tool like that to do what you want. You also might want to look into Geo-HMS to see if it has tools to do what you want to do. This works inside ArcMap (though I don't know if they've updated to 10 yet). ... View more