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lebronkahn

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About lebronkahn

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  1. HEC HMS extremely insensitive to changes in input.

    Hi Chris. I am using the version 4.2 >>> Send an email to or call Aquaveo Tech support I sure will but before I do: do they help with HMS? Thanks for the style sheet, I will definitely read into them. BTW, what is Snyder transform exactly? Is it just the Snyder Unit Hydrograph for the Transform Method. I will hang in there and keep cracking this thing lol. Appreciate your time and effort.
  2. HEC HMS extremely insensitive to changes in input.

    Thank you so much for your reply. >> I am certainly not an expert on the Kinematic wave method implemented in HMS. Me neither. First time doing this and apparently need more knowledge and digging up in the User Guide. But I have gone through it several times and still couldn't find out where I could have done wrong. >> increase the number of subreaches on your kinematic wave channels and/or on the overland flow plane. I changed the Subreaches # of Reaches from 5 to 50. The warning messages persist and the results didn't change too much. Couldn't seem to find Subreaches on flow plane tho. There is routing step option with default value as 5. I changed it to 50 as well and ran it again (with both value set as 50). Same deal. Couldn't believe it. >> Increasing your channel length by an order of magnitude and decreasing your slope by an order of magnitude As I posted in original post, I changed these two factors pretty dramatically without inducing too much change in the corresponding results. Plus, the lengths and slopes are acquired from the ArcHydro, not sure if I shall change them. >> show the Snyder method when you print the results. Sorry. I have to stand corrected on this one. It was not show on the result printout. Instead, it's the parameters printout. Parameters> Transform> Kinematic Wave. And it shows like this. Very confounded by it. >> Are you using the HMS reporting tools in the Tools | Reports menu? Somehow I couldn't do it. It asks for style sheet, which I have no knowledge of. Seems like I need to select a file. Please help if you know how to proceed. I use the same approach as you do. I will definitely consider sending the HEC an email for some advice.
  3. Hi, First I want to thank you for your time in advance. Any advice on this will be appreciated as I have been stuck on this problem for weeks now. Here is the situation: I created this basin model with 101 sub-basins and 100 reaches. Pic attached: "Basin Model" (there is something wrong with the upload, I changed it to URL) I am using one plane approach. No collector and subcollector channel information. For the sub-basins, I use "SCS Curve Number" as Loss Method and "Kinematic Wave" as Transform Method; for the reaches, I use "Muskingum" Routing Method. As show in the attached: SubBasin and Reach. In Meteorology Model: Precipitation is Specified Hyetograph I followed every step of the example in the HEC guide, and the model runs and can generate results. However, I found out that, no matter how much I changed the parameters, the corresponding changes in the results were minimal. For instance, the default value I used for Length and Slope for subbasin main channels are 100ft and 0.01. After I acquired the real value through ArcGIS (much longer length and much smaller slope) and put them into the model, the results were almost the same(1855.5 CFS to 1855 CFS). I also tried change the Route Upstream for some sub-basins i.e. from No to Yes. Still minimal change. Two things noteworthy and suspicious :every time I run the model, although the process can still go through, there will be warnings: Error in computing kinematic wave for subbasin SA 064; Estimation procedure for time step size failed to converge. And this will persist for a lot of SAs (sub-basins). Couldn't find anything Google associated with this warning message. Any idea? When I print out the results, the header will show: Method: Snyder Transform. I know for a fact that I didn't use anything called Snyder. Where does this come from. Please lemme know if I need to provide more details in order for this problem to be solved. Thanks
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