HEC-RAS Part 1: Basics

hello today we're going to learn some hack grass so let's start with downloading and installing the software once you type necros on your google it shows you the links for download and actually the official website for hikers so let's go to that one it's created by u.s army corps of engineers stands for hydrologic engineering center that's the heck part and raz is the river analysis system so that's why they call it hecras and this webpage shows you all the model capabilities this is the hacker's main window you have geometric data window you can use raz mapper to create flooding maps which we love the most and just an overview a summary of things here and here you have a link for download of course it's suggested you go over all these tabs to see what's new and all the documentation for the basically user manuals and everything but for today we're just going to do a quick introduction so get you all up to speed with using access so going to downloads you can see all the versions available so for windows uh 6.1 is the most current as of today and i'm going to download this right here if you're using other machines like linux you have that version and also you have access to all previous versions of hectares if you deliver the project maybe you deliver a project today to your client and three years later there is something they want you to rerun and modify and at that time request version 8.2 is current so you don't need to worry about that you can always come to our archive versions and install the one that you use back in the time so i have already downloaded this on my desktop it's right here uh hecras so that's the executable file over 300 megabytes and i installed it it takes less than a minute for you to install so i'm going to open the software and show you some important things so that's hector's main menu it's rather a small window everything is inside this like the geometric data window uh data for steady flow or unsteady flow sediment data water quality data and run and analyzing it so to explain things step by step let me first show you what comes with hecras what comes with hecras is basically if you go open uh in your document folder there is a subfolder called hack data once you install hacrats so here you have regress if there are other versions of hex software like hms for example you would see another folder here but so for today we're only doing a grass and then you will see example data a bunch of example data for water quality sediment 1d 2d modeling is here steady flow is the most straightforward one so if you start with that and you can model different things we can model the culvert but the manual chapter 4 has a very basic example we're going to show you that so now everything is populated once i open that file you can see the project is saved of course under the document folder and you have three more things plan geometry and steady flow so let me show you that one by one plan is basically a combination of your channel geometry and your flow data so if you want to run this you'll see your plan is called existing condition and that's also listed here existing condition run and there's a short id uh it's a combination of this geometry based geometry and a event that have a one two and ten percent chance of accuracy so of course [Music] you can you know have multiple geometry files in same project and then you can define a plan to link those so that's for the plan basically what geometry file and steady flow files should go into the model and then geometry is this window geometry data so it shows you a plan view of your river system you see there are two reaches upstream fall river butte creek uh and then they have a confluence at this point and sutter and then after that you have a downstream fall river so each uh segment you can have their cross sections cross sections you see it's uh it's a sort of a natural channel with a semi trapezoidal shape but but you can see here there are different stations so i'm going towards uh downstream i can have the other window shown so you can see how i move so i can go down so now i'm moving downstream and then you can see there is another channel cross section and for each cross section you would define what's the reach length from here to the next up downstream 500 and make sure uh you are understanding the units that you have in this model which is feet 500 feet you need to define your channel main channel which is this part main channel roughness also you have left over bank this is your leftover bank and this is right over bank in your floodplain and basically you define all these in the model i'm just giving you an overview what goes to each menu so in here you have your uh basically geometry you can add different things to it culvert bridge etc you can make this a storage area 2d modeling and all advanced stuff we don't want to do in this very first example so that's for geometry based geometry data next is the flow data so here you can have basically your return periods you have 10 year 50 year 100 year which are very typical data for running hydraulic models and as you can see you can simultaneously run the model with the three you don't need to make this change and save as a new file and run again so here the model allows you to run 32 000 simulations simultaneously that's that's really wonderful for that and you can see each um portion uh you need to define the queue for that and the unit here is cfs so for example your upper reach has a ten year of 500 cfs and the other tributary giving you hundreds so what goes to lower reach is 600 you need to define that and if you have another tributary that could increase your flow you would uh show that number here so basically that's for that and then you have uh you can run this is for run the guy is running so you explain in your plan what geometry and what steady flow you want to run you can change these have different plans without copy pasting your model so then you can compute to get some results so this is done and of course you can see the result in terms of cross-sections so now you can see how much water exists this is your 10-year you can have different plans showing so i'm going downstream you can see how things change uh this is the fall river lower reach you can of course run it for the upper reach if you would like and see how this might not be the best way to see it of course for flooding you can understand but if you want to have a idea of the whole model the profile view is a better fit so profile view now i'm showing uh upper reach let me change it to lower now you can see at each cross section what is the depth of water and how it is changing so let me have upper reach and lower which showing together for 10 years you can see how your water surface changes the green dash line is your energy grade line so you're basically adding velocity head to the water depth and then you can see how your slope is basically getting more flat as you move forward to downstream direction that's profile view and you can have also a 3d view of things so this is actually uh in some situations the most helpful one because at the same time you can rotate you can see how your channel and then you can play around with the view so now i'm getting a top view [Music] from most upstream towards downstream uh you can see if flooding happens in any locations and basically play around with that and of course you can get a bunch of tables and data table for data in form of tables always helpful in each reach you can see what's your fruit number what's your top width all the hydraulic characteristics that you're interested in so that's your comprehensive table right here and then you can also get a concise version of the table so that is for that and then always you have your documentation so let me go over to the documentation part uh documentation these are also saved on the same folder that is installed on your computer um user's manual is always a good thing to start an application guide and everything so for the user's manual this is where basically showing you all the good stuff for the system that you're using you know basically how to use each screen each window how to run how to play around with the table that i showed you so that's basically for user manual is a very advanced version of you can see it's over 700 pages 700 pages of what to how to use each button and each window in hecras and another important tool here for you is basically the application guide could be helpful and then also each specific uh document for like mod and debris flow uh hydraulic reference manual is the one that you would use for the equations so this is basically an advanced version of just what i just showed you and these are all helpful so for this one for example we are working with all the equations that goes into this so let's see all these equations uh transitions and everything in the channel all you know everything that goes to the grass for energy for loss and things like that so this is your reference emanuel uh how the model is solving things that you want so that's basically the one that you should be aware if you're using for a project for a thesis for a consulting project and everything all right uh before taking you to all the details of how to create a new file i would like to first show you a professionally created a grass model so you can understand uh what is expected for each buttons and menus in the model so this is what has been done for somewhere in san diego some warnings these are mostly because of different versions but basically you can see of course you have a project folder it shows you the direction you have a plan a plan is basically a combination of a geometry and a steady flow so you don't have to copy paste your model several times if you want to test different alternatives you can basically make a change in your geometry and create another plan like a plan seven zero here and just run the model inside the same project folder that you have so that's a very good thing for model management for uh geometry is this button so here i'm showing you an example of geometry being fed by arcgis data by gis data you can see the dm so each line here is a cross section line you can edit this cross section you can plot it you can do different things with it and there is a blue line with this arrow is your main reader line so just your main river line has a direction like this it actually goes upstream a little bit and goes downstream uh you can see different cross sections so if i start with this one then you can see that's a detailed model it also includes sediment this is your sediment field and you can see the gray line is the terrain data but then the model is being fed by actual trapezoidal channel information these are edited manually and you can see so you have a list of cross sections your most upstream uh cross-section usually the system that they use the largest number is all based on a downstream reference so your most downstream point is the lowest number and here you have 415 you can go towards the downstream you can see this number is being decreased the reverse station and um basically you have a culvert here you want to see if this culvert is flooded or not and then the model is able to simultaneously run different scenarios so that's why you see this blue line this blue line each blue line is this is for 10-year flood this is for a hundred year flood so you can see uh if i go back to the profile view of this river line you can see that in this scenario which is my two year even in two years the culvert is flooded so that's because you have lots of sediment in this example so basically just some definitions here uh you can press shift so you can pan this now if you press ctrl this changes to a ruler so you can measure things i can measure the length it also shows you d y over dx or your basically ground slope and basically key definitions here is that you have a main river line you sh it should show this arrow in the right direction and you have a set of cross-section lines these green lines these are your cross sections so this is a pond and when i get to the pond you can see that's now it's looking more of a pond now and there is a high heel here and everything like that so that's the stuff goes to your uh [Music] geometry window river reach you can draw it with this cross section window is the one that i have here here you also need to put your management coefficients and everything and it works with the set of station elevation information so you have this station zero so at zero your elevation is 12 it goes down you can see when i'm here uh it's a station 11 so somewhere here and then it gets this elevation 6.9 and it increases again so that's basically a you know very big data set of station elevation for each cross section and another thing goes to each model base next to geometry is your flow data you can simultaneously run your model for two year five year all the way to 100 year the model does require to have some boundary conditions so in this example because there is a measurement in the field we do know the water surface elevation at downstream to use it as a boundary condition and uh you know if you can of course run the model in unsteady with sediment with water quality but here is your run window and you can run the different combination of geometry file which i showed you and the steady flow file of course you might want to have different scenarios if you have the rehabilitation so what happens if you take all the vegetation out and run that and there is no need to copy paste this model you can have all this like for example if i show that geometry uh now that the rehab version uh basically now i'm dealing with cross sections that don't have sediment anymore and because the sediment is removed in this rehab version then when i plug the profile then uh the water surface uh is showing a little bit lower i need to rerun this to update this uh result but just giving you some ideas uh basically i'm editing the geometry file and running it again inside the same model so just going over what you expect to have now for for uh elementary use of regress you basically work with geometry flow data and you run your model all in steady condition everything else is advanced application and of course you can have a profile view of your water surface and your cross sections what's happening in each cross section so let's do all these in a very basic model and go step by step lastly before i start that i wanted to show you these two tables they can be very helpful uh instead of graphs that show depth you can get the actual number it gives you all the things that you learn in this course velocity top the fruit number everything and yeah let's so let's do that so i'm going to start a new file a very very basic file just to learn hey grass new project do you want to say no and desktop i have another test folder here i want to call this test 2 2 so then i do okay again us customer is good and now the next thing to work with is the geometry so geometry let me maximize this uh of course you need to have a river reach it needs to show in the right direction so one click and double click i want to have only two stations and i call this my river and this is my reach so river one reach one and okay so yes this is the direction i'm expecting i need to add uh cross section so this is not tied to any gis data to just keep it simple so things that you show it shows you here it's not really geo reference it's not into the escape but you're going to import the actual dimensions manually so now that you have that uh you can just have a cross section and it's showing you the risk you're dealing with uh you want to call i'm going to add new one add a new cross section uh big numbers are upstream numbers always so you have station 100 and station 100 uh let me draw something like this some over bank rectangular in the middle another over bank so station 0 i want to have let's say elevation 13 then i have five feet for over bank and then now one foot drop in the elevation at this same station i have now a vertical line because i'm in the rectangular channel board so nine then i want to go to the right a little bit for let's say 5 feet so my bottom width is 10 and the same elevation now i want to turn up for same height that they had and that's going to be 10 and 12. and lastly i want to have some overbank so 15 for a station and then let's rise it to 13 again so you can see some over bank main channel another over bank and then reach length let's say we have 100 feet of length for all sides and the reason that the model asks you different numbers is because if there is a band right over bank might be smaller than left but that's not the case here and of course for leftover bank you might have a rough number maybe 0.1 but for the main channel let's keep it as the famous number of 0.015 so i'm applying it it's going to show everything at point one because i haven't yet defined the boundary of over bank and main channel main channel bank station left bank is my five right bank is my 10 and apply so now you can see these red but red dots red dot shows the boundary you can leave the contraction expansion coefficients as default so that's one of your cross section at upstream you want to replicate this figure at downstream and now basically we want to create another one add a new cross section and let's call this one number one because that's very close to my downstream and uh just one foot we don't really care beyond that you can leave these and then you need to draw a shape again to to do that at zero i need to go back to my up let me apply this i need to go back up i have uh 0 13 so let's reduce everything by two feet maybe zero eleven and now five feet ten 5 feet 7 now let's add another 5 to the station so go to the other side then 7 then [Music] at this location i want to rise up 10 10 and lastly i wanna go five feet away five feet away and increase it to 11 apply it so this shape appears again but i need to define the boundary lines so you have over bank and main channel so again 5 and here is 10. for the boundary of main channel and over x i apply it and then it shows in the right way so basically it appears for you the bottom and top cross section so you have everything needed for this part so you can close this of course you want to save the work you did save geometry gm test okay close it now import your queue data qradar you can see at the same time you can have different numbers of cfs run let's leave it as one and 10 cfs is good so i'm applying data so 10 cfs is what i want to run you see the unit here is shown as cfs but you need to define your boundary condition the upstream um we can leave it but for downstream you need to have one so let's say i want to run for a normal depth with the slope of one percent and apply and save so that's my flow test and now i want to save this no i don't i have everything i don't have a plan so the plan when you click on run run steady so around on city and everything is advanced but run steady so basically you can have an id just t t and then that's good you have a geometry just one version of it you have flow one version of it you just want to run it in a sub critical mode to see what happens and run boom so congrats on your first successful hagris run so you want to see your results now your results cross sections so basically it's showing you you have half a foot your bottom elevation is seven so 0.49 you have half a foot of water in your downstream cross section let me move to upstream one again you have uh half a foot which is 0.49 foot of water in your upstream so basically this is a uniform flow i am showing you the cross section so let me now show you the profile so that makes sense to you why i'm saying this is a uniform flow this is a very uniform flow and the profile view can show you basically you are a normal depth which is also your critical depth this red dashed line is the critical depth which is happening exact same elevation as the water and in green line is your energy grade line so water surface plus the velocity head are very helpful information so far you can make this uh a 3d here and the 3d there is a 3d view so just say yes and now you can see this is your channel very uniform and of course you can make all useful tables energy great elevation energy a slope everything with vetted parameter everything you have learned in this course basically cfs is 10 and uh also this big table showing you numbers for each cross section root numbers is around one is exactly one actually that's meaning uh your flow is running as a critical flow but is that the case always no in this particular condition because i have a rather steep slope it's happening to be a critical depth so now i want to change it to show you that's not always the case if you make the slope milder i want to make this slope very mild at the boundary condition and save and run so let's see when i make it mild then my cross section now in the downstream one i have around two feet of water but at upstream it's half a foot so this is not critical anymore the profile view shows me it's not critical at all towards the end you can see whether surface is touching the energy grade line basically that means you have a very very slow velocity here because the slope is super mild it makes the water to slow down almost steel and you can see your critical depth is going to be half a foot of depth but your water flow is not following that that's a very very interesting thing to show with hecras you can test all things you don't need actual physical form you can test many things uh you can run many numbers for cfs at the same time in the model and of course if you want to see it in the 3d mode then you can see again it's not uniform it's increasing depth towards downstream and to tables of course your velocity is dropping a lot you start with something or near the critical uh flow but that works downstream is very subcritical that's the change you can do and you can study with hecras you can make other changes you can have now maybe two different values for q running at the same time so i'm changing this to two and then that gives me that gives me uh another column so now i want to run it with 50 cfs at the same time and apply it and then of course you run and it runs both for 10 and cfs combined so your figure is going to be busier if i show this plot so of course you need to bring in the profile so i click both and uh so let me get rid of one okay so for number two uh it's gonna be basically uh first kind of flat water surface and i want to show it in this mode again it's basically lots and lots of water so we're not showing it in and so the water is basically in the upstream situation it's okay makes sense uh leaving the main channel going a little bit towards the over banks but at the downstream is fully flooded you can see it's even higher than the depth that i had for my over bank so that's basically lots of water you have in this tiny channel uh so if you're designing something for this then your button width of 5 foot is not helping you you need to make it 10 you need to make changes that's how you design things with headgrass and uh that's that's it for basically how to do your first uh hecras model uh basically save and geometry and uh flow for steady if you want to do unsteady quasi-these are your options if you're on or sediment or water quality that's your options and of course this is run for steady of course you have run for unsteady sediment water quality and everything this is uh the window that takes you to the gis work so you can incorporate gis data in your model so that makes uh the process of creating cross-sections a lot easier and there everything else is for understanding the results so i hope you enjoyed this elementary first step video to heckras and we will have you for more videos on this topic

Channel: Hassan Davani

Views: 2,638

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Id: T0BpWRxeOhM

Length: 34min 54sec (2094 seconds)

Published: Tue Nov 09 2021