Latest Contributions by MarkBoucher

I recently experienced this.  I was creating a DEM from LiDAR (LAS files). I found that I had the DEM grid size different in the settings of a couple of geoprocessing tools. I had one process using 1' DEM and another using 2'. Had very strange patterns. Once I discovered my error, made the correction, and the phantom lines when away. ... View more

Similar question here: https://community.esri.com/thread/110326  ... View more

I found the 10.6 versions. Are they working? ... View more

This is a common error,  the solution to which eludes many. The answer could be found in ArcHydro Problem Solvers. Go there and search the page for "hresult" and you'll find some discussion on it. One of the tips is to run your project on your local PC and not on the network. That is, put the mxd and all geodatabase the project creates on your local machine. There is something about saving the output over a network that slows things down and causes problems. Also, put your own data in a geodatabase (agree stream, inner walls, etc.). This is more stable than shape files and for some reason I stopped having errors once I did this. Best, Mark ... View more

Here are links for how to understanding (and removing if necessary to fix the trace tool problem) the spatial index. Add Spatial Index—Help | ArcGIS for Desktop  Remove Spatial Index—Help | ArcGIS for Desktop  Or maybe you can reset/rebuild it: Rebuild a spatial index—ArcGIS Help | ArcGIS Desktop  You may need more than a basic license to work with the relate tools. ESRI note:             "License: You must have ArcGIS Desktop Advanced or Desktop Standard to rebuild,             drop, or re-create the spatial index of a feature class in an enterprise geodatabase or database." Make sure you head the warnings before you rebuild your spatial index! I have had problems with the geographic extents of my project are not correct. These are related: An overview of spatial references—ArcGIS Help | ArcGIS Desktop  Mark ... View more

I think what you see happening is normal. If you click on the pixels to see the flow accumulation value, you will see those at the bottom of the watershed (along the strlnk line and the last pixel before leaving the subbasin) are related to the area of the watershed (multiply fac by pixel area).  The confluence would NEED to be inside the next downstream catchment/subbasin/watershed.   I also agree that what we are dealing with is a digitized representation of something that is analog. So we have to except a more “grainy ” result in our analysis. Hydrology is a subset of the overall Civil Engineering discipline and C.E. can also stand for "close enough".   Mark Boucher, PE Senior Hydrologist Contra Costa County Flood Control & Water Conservation District ... View more

Katie, I downloaded your data and went straight to DEM reconditioning and had now problems. I am using 10.4.1 and can't use 10.3. I ran the reconditioning and it worked fine. I also ran my typical process on the original DEM (not reconditioned) fill sinks-flow direction-flow accumulation-stream definition-stream links-catchment grid delineation-catchment poly processing-drainage lines. Everything worked fine.  As for having the flowline date in a geodatabase, I've always found geodatabases to be more stable and my practice it to put the data in a geodatabase as a matter of course. So, your finding conflicts with mine and I'll have to keep a heads up. I had problems in the past with versions of HEC-GeoHMS and ArcHydro not being based on the same version. When I "mixed" the versions, I would run into problems. One thing I do is ignore streams and rely on the DEM to define the streams except when there is a problem area like a bridge or embankment that the DEM "doesn't know about". I set lines and burn through those. I do burn in pipes especially in the flat lands. Attached you can see a version of the DEM with the streams burned in (reconditioned) with the drainage lines from the non-reconditioned (non-burned) DEM. The drainage lines do not always follow the NHDFlowlines. This tells me that the flow lines are likely manually created or are out of date (ie. based on an older DEM). Best, Mark ... View more

Make sure all of the data is in the same coordinate system and the processing extents include the work area. Mark Boucher Sent from my iPhone ... View more

Here is an example. I found this gauge by zooming in on the map at CNRFC site (see first image).  The gauge is on the San Joaquin river south of Tracy and Manteca, CA. The flow at this point at 10/4/17 05AM now is projected to be 2,425 cfs (see second image is for the same station). The data is "current" up to 10/3/17 08AM. (Not sure why the actual gauge readings are not up to date. Could be a summertime practice to only report once a day.) The same location has a flow of 2,168 cfs in the National Water Model (NWM) for 10/4/17, 05 AM (see third image).  In once sense these flows are very comparable and I think the NWM is doing pretty good to get this close. In a time of flooding, there would need to be  a correlation between the stream gage reading and the NWM.  I'm certain that the CNRFC would share the gauge data with anyone. I suspect there is already this kind of collaboration going on. ... View more

I would be curious how the NWS responds to this. Also, it would be very important to compare these results to the NWS River Forecast Centers so that there is a cross check on the accuracy of the output. They may be an important partner in developing the accurate local models that work with this. ... View more

Ammara, I think we are still on 10.3. I'd have to check once back in the office on Monday. Mark Boucher Sent from my iPhone ... View more

Another helpful tool set can be found using HEC-GeoHMS. This is a free ArcMap tool that has the basics of the Arc Hydro tool. The geoprocessing tools for Arc Hydro are in this tool but they are somewhat simplified. That is, you could use the GeoHMS tools just like the Arc Hydro tools. GeoHMS was created by ESRI for the US Army Corps of Engineers Hydraulic Engineering Center (HEC). It has additional tools to build HEC-HMS models, something I suppose you don't need. When you install HEC-GeoHMS it will also install the compatible Arc Hydro tools. ... View more

Crystal, If you can't use StreamStats, then you either can delineate the watersheds by hand (quick and easy if you just have a few) using topo maps or heads-up digitizing in ArcMap or with another tool. I assume you're going the ArcMap route and want to automate (not digitize) the watersheds. Spatial Analyst has tools you can use and Arc Hydro uses the SA license to perform all of what you need. The process for making a hydrologically correct DEM from which the watersheds are then delineated isn't hard, but it takes time to understand the concepts. I "authored" and respond to questions on thread called ArcHydro Problem Solvers. Most of what I know (and ways around problems I encountered) can be found there.  It's not a "course" on the Arc Hydro, but it is a start. Mark ... View more

Sometimes I save and close Arc Map then reboot and this fixes the problem. I've often wondered if Arc Map has trouble with the "undo" list. That is, if you've made a lot of changes with saving/reopening the .mxd, maybe it can't handle that and needs to have a "clean slate" to proceed. Only a theory... ... View more