Hydrologic Modeling Using HEC-HMS (5/9) - Assigning CN to sub-basins

[@AbdulhamidAlkali]

Good day. Thank you for the video. I have tried assigning the CN numbers to my sub-basins and clicked on the "Apply" button. However, when i click on the "Characteristics" under the "Parameters" toolbar, it does not show me the basin characteristics that will help me in obtaining the "Lag Time". My study area is 38,000Km2. Please I need your advice. Thank you.

[@raziehizanloo574]

Thanks again for good teaching. I wanted to know if it is possibke to run the model in 1 Day step (for examle having precipitation in one week) how we should set the cn number.because in the second and third day of having rainfall in the watershed, the cn will be changed?

[@nehemiahstewart]

I'm curious of the quality of the bathometry of the channel that HEC-HMS rastered from the .dem. A quick cross section could tell the story. Great video! Thanks!

[@andyharvielmawblei2671]

Can you make a tutorial on how to make the CN grid tif of the study area

[@hydrologyvideos8253]

sure. it will be posted in the near future! if you know qgis, try following this tutorial: web.ics.purdue.edu/~vmerwade/education/qcngrid.pdf

[@siragree2630]

Hello sir, can i use ArcGIS instead of QGIS in making the CN grid tif. Thank you

[@hertabuss289]

I do not get the basin characteristics computed. Any guess what could be wrong? I do get the subbasin area and lengths of the reaches, but no concentration times.... Any help much appreciated! Thanks for your videos!!

[@hydrologyvideos8253]

make sure you have CN value for each sub-basin.

[@AbdulhamidAlkali]

Yes also experiencing thesame issue. Will it run regardless of the CN value? @@hydrologyvideos8253

[@arvinlaxamana6115]

Where did you get the cngrid.shp?

[@hydrologyvideos8253]

Good question! There is a process to create this. That video(s) will be uploaded in the coming weeks. There is also a link for the tutorial in the comments section.

[@arvinlaxamana6115]

I tried following the steps in the tutorial using QGIS. However, I don't know where to get a land-use raster file of our country. Do you know a website where I can get one? Thanks!

[@hydrologyvideos8253]

@@arvinlaxamana6115 which country? I know where to get it for the US. I am not familiar with data availability in other countries, but I do know that there are global datasets available.

[@arvinlaxamana6115]

Philippines

[@hydrologyvideos8253]

@@arvinlaxamana6115 I do not know how to get landuse or soil for Philippines.

[@KamranKhan-gx6sk]

Hello Sir., When i export subasins to ArcMap, it on shows data of on subbasin, the rest is missing. While in HEC-HMS all basin are showing lat/long, and other information., please guide...

[@basitbaloch4947]

i Have multiple outlets. How can I know the discharge of Multiple outlets, as an outlet can have many sub-basins? As I am doing a project with multiple outlets but I am not getting the discharge of multiple outlets separately. in which there are many sub-basins.

[@hydrologyvideos8253]

HEC-HMS is mostly used for dendritic river systems with one outlet

[@maf4421]

Hi, how to setup a model for more than tow outlets. Thanks

[@maiya_angel]

Hello, how to calculate cn without using gis in hec-hms 4.10 version?

[@hydrologyvideos8253]

I do not think 4.10 is out yet. I do not know a way to compute CN grid in hec-hms.

[@maiya_angel]

@@hydrologyvideos8253 there is beta version of 4.10 in internet.

[@maiya_angel]

@@hydrologyvideos8253 anyway is there any direct method to calculate CN in hec-hms higher versions?

[@rohitnayak9952]

The quick and approximate method to create CN map raster would be assigning CN values to specific Landuse vector table by making assumptions of fixed soil type for all the soil group.It requires basic GIS skills🤞 Note:this can be done for concept design/preliminary Storm design for urban catchments

[@basitbaloch4947]

Sir can anyone guide me where I can easily get raster file or soil data.. as I facing issue uploading file at Input value raste at zonal statistics table

[@hydrologyvideos8253]

web.ics.purdue.edu/~vmerwade/data/hms_data.zip

[@SakshiThakurFood]

From where that cngrid.tif file came, please tell me

[@hydrologyvideos8253]

it is provided with the input data. there is also a separate playlist on how to create cngrid

[@Tobby4063]

Very good videos. Thank you.

[@riverpx6175]

how to get cngrid file？

[@hydrologyvideos8253]

check out this video: kzbin.info/www/bejne/hZaZeIykm9KUhq8

[@lalkhan162]

Thank you for this great video series. I have one question, in this video, you have shown how to calculate the mean value of a curve number for a sub basin. Can you tell us how to calculate weighted mean value of curve number for a sub basin. Thank You

[@hydrologyvideos8253]

ince the values are based on a raster for each sub-basin, area weighted mean will be same as arithmetic mean. You can calculate the area weighted mean for the watershed. CN = CN(i) x A(i)/sum of A(i). s

[@lalkhan162]

@@hydrologyvideos8253 Okay. Thank you for clarification.