Advanced Modeling 1.2 - 2D Modeling Demonstration

so what i what this demonstration is about is to show you how easy it is to create a 2d model this demonstration is really geared towards people haven't done 2d modeling yet or just maybe tried it once or twice okay and so if you've done some 2d monitor ads this is just going to be review for you but it's really so this demo is really geared towards the new people in the class and so here i've got a erasmus only thing i've done so far is i said file new projects i already did that i got a project and i haven't created any geometry or anything so i'm going to go into raz mapper and we're going to walk through the steps so here i am raz mapper and there's nothing okay so the very first step is to go to project and set your projection so you have to have a spatial projection okay so this editor is going to come up and there's a plot for a projection file so i'm going to hit this button to go out and find a projection file and i happen to have one stored in the terrain and it's a state plane projection file now it has to be an arcgis projection file okay and then we're just going to say okay that's the first step you got to do that first do that before creating any train or anything set that projection file well the next step is we got to have a terrain model to do any 2d modeling so we're going to create a train so we're going to say create a new terrain and up comes this editor and i'm not going to go through the details of this editor because rat cam is going to go through the details that are in a whole lecture but basically i'm going to add some files that are out on my machine i'm going to add i have two two terrain files and one's just a general um terrain for the whole area but the other one is a channel model that i made from a 1d razz model that's from what was 1d survey cross sections and i want the channel part of it the channel only to trump the regular terrain so i have it on top okay and then i'm just going to go ahead and say create terrain and again cam's going to go through this editor in detail so don't worry about understanding everything that i'm doing that's not the point of this you'll get the details so there it is there's the terrain okay and if you see we're going to work in this area but this channel is a separate model terrain model that was created from 1d cross sections then this rest of this terrain was just a dem a 5 meter i think it's 5 foot cells okay okay now what i like to do before i create the 2d area you don't have to do it this way but what i'm going to do next is i'm going to create a land cover layer that i'm going to use for manning's in value so i'm going to go over to excuse me rasmapper and hit map layers right click create a new raz layer and say land cover layer and again that same type of editor comes up for a terrain where i can add files and here i'm gonna add first thing i'm going to add is actually a national land cover data set from the usgs that i have i have the 2016 national land cover data set for the whole country it's not that big okay so you can download it for the entire us okay in addition to that i'm going to add a shape file that i have that was drawn in raz in the area where we're working in but i want the shape file to be on top so it trumps the national land cover data so i'm going to click on it and i'm going to move it up okay there's the national land cover data set it has various classifications and then my shapefile that we're created just has you know six that were drawn by hand so this is the data we're going to combine together to make a land cover data set so i'm going to hit create it's done and then there it is so if i open up the map layers there's my land cover and if i move around i can see that in the outer area i have this national land cover data set and it's showing me this you know develop medium density and low intensity okay but inside i drew some polygons so here i have a park here i have a building here i have another building i wanted these larger buildings on purpose so i could define separate parameters for the buildings like really high end values okay so there's my land covered data set now the channel is going right through here and the national land cover data sets do a horrible job there is some open water but then there's also it says medium intensity urban right in the center of the channel well we know there's not medium intensity urban right inside the channel okay so the the accuracy of the national data set for channels is horrible so one of the things you're probably going to want to do in raz is create your own classifications for the land cover so here what i'm going to do is i'm going to edit and i'm going to create a polygon around what i consider to be the channel area and i'm going to call it main channel so i'm creating my own last cl classification called main channel and i'm going to give it my its own separate envelopes now in a larger study we might want to create multiple classifications in channels so we can give them each separate n values okay so as many places where you think the n values should be different in the channel you'd create a separate polygon we're just going to do one so i'm going to go ahead and zoom in on this where we're going to do this and i'm going to right click and i'm going to say edit layer now i'm going to turn off the land cover because i'm going to i'm going to draw a classification along the main channel okay now this is going to take me i'm not going to do this super accurate like i normally would and if you talk to cam he would tell you that i'm extremely anal about creating polygons along channels and it really is tough for me to do a bad job and i hate it but we're going to try to do this quickly in interest a time so this is not going to be perfectly along aligned along the bank because it would take too long and we're just trying to demonstrate here now i'm left clicking to get a value and if i right click it re-centers so i don't have to stop and click a different button or anything like that so i'm going to come out here this area is going to be all wet so i want it to be part of my channel n value recenter and we're just going to go down to about here and then i'm going to start going back camera gary as you're doing this even though you can do all of this in ras mapper do you find that there's some our gis tools that are like snapping that makes this um maybe a little bit more accurate or would you recommend any tricks i know you can do you can digitize everything in raz mapper we no longer need gis but if there's some features that uh that you find useful still using it to kind of clean things up with respect to polygons or brake lines no well i was just going to say for me i stay in raz mapper because i am just a part-time user of arcgis so i'm i'm actually way more comfortable using the tools and rather matter but cam is a big-time arcgis user so let's get his perspective on that so uh my comment is we're never we're never going to be replacing the gis there's just too many tools and and uh things about the gis um different gis software has gotten much much much more complicated every year and it makes it a lot harder to jump in and just do something simple and so we're trying to replace that that requirement we don't have snapping in raz mapper right now that's something we know we would like to have we do have clipping tools so if you're trying to marry the edges of polygons it's really easy you can create your two polygons and then clip one and it'll throw away the overlapping area so we do have that so i don't think there's anything you you need in capital letters like need in the gis but obviously if you're really great with a gis you probably can be a little bit faster over there okay so i finished the polygon i'm going to call it main channel again i would probably do lots of these for the channel and i might call it channel one channel two whatever i'm gonna put in an n value already which you can not any percent impervious because we're not going to do infiltration and say okay so now when i zoom out okay and i'm going to stop editing and i'm going to save yes so now when i go over top of it i see main channel okay the next step though is we're going to populate this thing with n values and i'm just going to put n values in here don't worry about the invalids i'm putting in they're not going to be accurate i'm going to try to make them reasonable but don't hold me to these n values you know they're just for a demonstration okay so we got open space maybe 0.35 we got a building now a building i am going to talk about i'm going to put an n value of 100 for a building and the reason is i don't want water to be able to go through a building so if i have an value of 100 even though i don't have the physical building and their water is going to come up and it's going to hit that m value 100 it's going to go around it and some is going to slowly seep in which is kind of what happens with the building as you're putting that in i've got a quick question on the channel n value so we all know that the n value changes quite a bit in channels depending on vegetation et cetera i would assume you would put in multiple polygons to define different values within that channel is that a correct statement so the the good thing is in this classification even if you don't in the classification um later on you'll see for each geometry you can actually create what are called n-value override polygons so if later on when you go to calibrate you realize you need more n values you can make additional polygons per geometry and you can override the n values for those polygons anywhere so here i'm trying to do a good job in the main classification to get a good base but when i go to calibrate i'm going to want to adjust n values everywhere so i'm going to use those override polygons so i can either make lots of channel polygons here if i want which is a great idea or i can do them later or i can just use the override polygons for adjusting multiple ones up and down percentage-wise okay so there's my n values and i'm done so now when i move over not only do i see the land classification but i see the end value so there's my building of 100 medium density 06 uh trees 06 etc okay do you guys use a specific report for your end values for the nlp delay or d like with um because i know they vary depending on like so there's some um guidelines on end values in the raz hydraulic reference manual for different types of land cover and land use but they're just starting values when you go to calibrate these are not even any guidelines you find anywhere are only going to be starting values and you're going to have to adjust them when you go to calibrate to events okay okay so that's it for the land cover now let's go ahead and create a geometry so i'm going to actually right click on geometry and you can add a new geometry right in ras mapper you don't have to go back to the geometry editor so i'm going to say new geometry and i'm just going to call it base geometry geometry data okay and then i'm going to turn on the 2d area and specifically the perimeter and i'm going to right click and say edit geometry so now i'm going to draw a 2d flow area perimeter and again i'm going to zoom in down here okay and i'm going to turn off the land cover data for a second now i'm going to there's a road here i'm going to start my 2d area right along this road is the upstream end okay and i'm just going to make it kind of big i'm i want to make sure it encapsulates all the water so i'm going to go to high ground in this area because i don't i don't want to have to redraw this two deer and i'm going to come up here i'm not going to go way up this tributary because this is just an example but we're going to come down and we're going to go over and again i'm on high ground at basically an elevation where i think well that the water's not going to now let's say i don't like that point it just drew i'm gonna hit control z and back up and go over here and i can control z as many times as i want okay now i'm gonna i'm gonna cut this off i'm not gonna go too big with this it's just a demonstration and we're going to head back now to where we started again i'm on high ground where water's not going to get too and then i'm just going to double click the last point and i'm just going to call it 2d flow area now once i name it it automatically brings up the editor to create the mesh and ras mapper and it even automatically puts in a cell size of 100 by 100 that doesn't mean anything that is not like the recommended cell size okay that's just a default the cell size should be you need to think about what's the appropriate default cell size for the problem and generally the way they do that the way i do this is i use as the first cell size like the largest cell size i'm going to use because then i can add refinement regions to make smaller cell sizes in different places but we're going to go ahead and keep 100 and i'm going to say generate computation points and close and there it is okay there's my 2d flow area now in addition to that i need to add boundary conditions to this thing so we're going to go back over here this is the upstream end and then i'm going to turn on the bc reference lines and i'm already editing still so i'm going to be on the new add a new feature or not edit but add a new feature and boundary conditional lines we want to draw left to right looking downstream so the flow is going this way and i just want the water to come through this roadway so i'm going to just the boundary condition lines the external ones we draw outside of the 2d area don't go inside at all if you want it as an extra boundary you have to be outside the 2d area so i'm going to just start here and go to there and i'm going to call it upstream inflow okay now i'm going to move downstream and the way i'm moving downstream is i'm holding down the shift key to get a panning icon and i'm moving down and i can use my my center wheel to zoom in and zoom out now water's going this way so i want to draw from left to right looking downstream so i'm going to make this one larger because it water can go out in this flood plain too so i'm going to say this boundary condition goes all the way up to here and i'm going to call that downstream outflow okay okay so now we're going to stop editing and we're going to save that data so that's pretty much everything i want to create for the the geometry and raz mapper but before i leave i need to associate with this geometry i need to go up and right click on the geometry and say manage geometry associations i need to associate the terrain i want to use and what i want to use for envelopes now since there's only one terrain that automatically defaulted to that train but if i had more than one i would pick the train i want to use with this geometry and then for n values i'd pick that land cover data set that i created we're not doing infiltration so i don't need an inflationary representative previous and we're not doing sediment so i don't need those to associate with the geometry just terrain and end values those are a requirement you have to have terrain and n values to do 2d modeling so we're going to do that okay so now i'm just going to close razmapper now i'm going to open the geometry editor i'm going to open that file that i just created in ras mapper because you have before you can add boundary conditions you have to have a geometry file opened okay so that lets raz know oh you want to add flow boundary conditions with the currently open geometry file so i've got this geometry file opened now i can go to the unsteady flow data editor either as edit on city flow data or i can pick this button which is the unsteady flow data editor and what i want to do next then is i want to put in the boundary conditions that i created so for the upstream inflow we're going to use a flow high draft so i click on the cell for the upstream inflow then i pick a boundary condition type notice not all the types are available because it already knows that it's a two dimensional flow rate boundary condition and there's only four types available so i'm going to pick flow hydrograph now here i'm going to enter the data into a table and i'm going to use hourly values and i'm just going to make up a flow hydrograph so i'm going to start at 5000 cfs and i'm going to go for 12 hours and i'm going to go to 20 000 cfs and then i'm going to go to 36 hours and i'm going to go back to 5000 cfs now raz has this cool feature it says interpolate missing values so i don't have to type them all in it'll interpolate the rest and then i want to look at that i can say plot and it takes a minute to load and there's my hydrograph going from 5000 to 20 and back to 5 over 36 hours now one other thing you have to do for flow hydrographs with two deer is you have to give it a slope at where along the stream you really want what's like a water surface or energy slope but the idea here is it needs a slope to use manning's equation in order to figure out a water surface of that boundary condition and then to how to figure out how to distribute the flow amongst the cells along that boundary condition so i'm you're required to enter a water surface slope in that location of where the boundary condition is okay now you can use a terrain slope if you don't know the water surface is a as a rough value but after you start making runs you might want to go up and refine that okay so that's all we need for the flow hydrograph now for downstream um we don't have a a known flow or a known stage okay so we're going to use manny's equation or what's called normal depth and it requires a slope also and i'm going to use the same slope in this case and what it's going to do here it's going to use the cross section it extracts for that boundary condition line and then manning's equation and this end value for any given flow it's going to compute a water surface and then from that water source it's going to figure out how much flow to take out of each cell along that boundary condition line now for initial conditions i'm not going to put any initial water surface in this 2d or i'm going to leave it start dry okay so i'm going to leave that blank and then i'm going to say file save on study flow and let's just call this demo flood event and so there we have it we have terrain and geometry and we have flow now we need to create a plan like we always do in raz so i'm going to come up here now you got to run the geometric preprocessor in the unsteady flow the post processor is only used for 1d so we don't need that okay um so we can not worry about that but i do need to put in a time window so i'm just going to use one that i didn't when i originally created this pre-february 2021 starting at time zero and i'm going to go to 4 february 2021 at time 12 so that's 36 hours of simulation because i only put in 36 hours of flow i'm going to use a 15 second time step why do you think i'm choosing 15 seconds what do i know about this model already to give me some kind of judgment that i need the time step less than a minute maybe well i know the cell size right what cell size did i pick 100 underfoot so normally in a flood what's a typical velocity range in a channel three four five feet per second yeah five feet per second that's a good one so at five feet per second how fast does water go through 100 feet 20 seconds right so if the velocity is faster than that so i'm picking a time step that i know that's going to be close to like the time it takes this water is going to move through a cell and i might have to make that smaller later on if i have some problems but i might be able to get away with it bigger but it's a starting value now for mapping output i'm going to do every 30 minutes and then for my hydrograph output i want to be more detailed for hydrograph plots i'm going to say every five minutes now this detailed output interval is only for post-processing for 1d modeling since there's no 1d model i don't care about that then one other thing i'm going to do is i'm actually going to go to the computational options you're going to get a whole lecture on this so don't worry about it there's a 2d flow tab and there's this thing called initial conditions time and i'm going to set that as an hour and what that does it says run this 2d area for an hour with a the inflow at 5000 constant and i'm just going to do that to get water in through the channel okay so i'm going to run that 5000 for an hour to have water all the way through the channel before i actually start my event so that's called a 2d initial conditions time then i'm going to go ahead and save this plan i'm going to give it a name call it demo flood run for the you can give it a long title and then a short id i'm just going to use the same thing okay and that's it so now i should be able to hit compute and it should run unless i made a mistake or i forgot some data so it's going to do some data checking first but it looks like i didn't miss anything so it's doing the pre-processing of the 2d area that's done and now it's running the model okay and since we don't have a lot of cells it's going to go pretty quickly all right so that's done i'm going to close that i'm going to close these guys i'm going to go to raz mapper because that's the only place we can look at output for 2d other than the hydrograph plot and i'm going to turn on results and i have one plan which we just created and i'm going to look at the depth so this is the maximum depth that occurred during the event but i can also click on depth and then i can animate that so let's go ahead and animate that here's what happened during the event okay and i can bring that back and you know i can i can go through it more slowly so maybe i want to zoom in here and i can walk through it so what do we think about this model as it is do we think it's a detailed model no there's no brake lines there's no brake lines what about the channel the over banks are not well defined over banks aren't defined they're not defined at all right because i don't have faces lined up with the banks do i so like in here this water let's back up watch what happens this water since i don't have faces lined up with the high ground of the channel it has no knowledge of that high ground of the channel so watch what happens to the water when it gets up high enough it jumps out here and there's really some high ground right through here that i should have aligned for the channel and had faces along so it wouldn't get out of the channel until it got high enough to go over that high ground but because i don't have faces lined up with the banks of the channel it has no knowledge of it it only has knowledge of the terrain along the faces okay so here water can get into this cell right here water's getting into this cell and because water is one elevation well this part of the cell's that low also so it puts water out here well if water can get here it can cross this face and go to here it can cross that base to go to there okay it can cross this face and go to here so that's the problem with this if i don't have faces along the channel i'm not respecting the high ground of the channel and i do not have an accurate channel model at all and as far as the over banks i don't have any brake lines respecting these roads and so forth now i'm not going to go through and create a detailed model but i am going to go show you how to quickly use a refinement region for the channel because we can do that pretty quick okay so let's go ahead and go back to our geometry and go to our 2d area and turn on refinement region and before i do that i could draw this refinement region but i've already drawn a channel polygon didn't i when did i draw a channel polygon for the manning's end right so one thing i can do is i can go down to my map layers and i know that i made a classification layer so i'm going to start editing this layer and i know i have a classification layer and then i'm going to i'm going to select the channel polygon and then i'm going to right click on this and say copy selected feature so that copies that polygon into memory so now i'm going to come up to refinement region and i'm going to say edit and now i'm just going to right click and i'm going to say paste feature i'm going to turn off the map layers and lo and behold now i have a refinement region polygon already in there okay i didn't have to draw because i had already drawn it or if i had a shapefile out there i could import a shape file either way so the next step though is to define the parameters of the refinement region so i'm going to right click on it i'm going to say edit refinement region properties and you give the refinement region cell size for the interior i'm going to use 50 feet but then you also give it a cell size along the perimeter i'm going to use 50 feet along the perimeter they don't have to be the same i could use 100 along the perimeter 50 inside then there's this thing called near repeats if you want to repeat the cell size along the perimeter if i want to use 50 and then another 50 i'm gonna go ahead and do one bar spacing if i leave it blank it goes back to the nominal cell size of the two dairy which is 100 so i'm going to leave it blank and then this one cell protection radius says if i have other refinement regions or break lines near this don't screw up the cells along this refinement region make sure they stay intact so that's all a good thing so i'm going to say okay now i'm going to right click on it and say enforce the region and it actually makes the mesh now there's a couple of red dots and what it's saying is there's an error it says maximum of eight freezes per cell so i have three locations where i have cells that have more than eight faces the easiest way to fix that is to add computation points so i'm going to click on computation points i'm going to zoom in and sure enough if i look this cell has one two three four five six seven eight nine faces so i'm simply gonna add some new points one here maybe one there now that cell's fixed so now i'm going to zoom back out and i'm going to go over to the other two cells that have the same problem and i'm going to add a computation point here in here and then i'm going to come up to this cell and this one's got like 10 faces so i'm going to maybe have to add more than just a couple okay it looks like i got it and now if i zoom back out there's no cells no red dots okay and so i'm going to stop editing and i'm going to save the edits okay so that i've just added a refinement region to that to the area i'm not going to go ahead and the next step would be to add break lines in the interior i'm going to skip that step so let's close this i do want to open the raz geometry so you can see there's the refinement region in the geometry now i'm going to go ahead and just run it now it's going to take a little longer to run because we added a lot more cells inside that channel we're using 50 foot cells instead of 100 foot cells do you ever notice those red mapper like uh wet spots that are outside the channel is that ever just from like a bug because i've had that before where it has like enforced the channel and they still give me like random spots that seem wet that shouldn't be wet well again it depends on how you align those faces and if water can cross a face and go to a cell okay that that so the what's gonna if in some case you you might because the train is sloping so much the only way to get away with that would be to have really small cells so it could go to one cell the next to the next the next so there's gonna be on some level you don't you're to have to live with some of that you know what i'm saying is that like when water's just first leaving yeah it might be a little spotty right there and you know that it really traveled over land continuously but because the cells are larger it only has one water source per cell it can't show you that because there's not enough cells okay but if that's not really germane to the final problem so what right once you get to a higher flow and if that's covered then you've got your right answer anyway now it's still accounting for the travel time through the cell so don't worry about that part of it okay okay so now we've got this more detailed model and when i animate back in that area i'm going to see water coming out a little bit more nice now here's where it did jump a little bit here right and again it went into this cell but because this is really steep sloping and it can only get one water surface for this cell the water can come into this cell but the lowest point in the cell is here and so it doesn't show it flowing down the cell because it can only have one water surface per cell does that make sense so if i really wanted to see water water flowing down the steep terrain i'd have to use really small cells so there's going to be some limit where you're just going to have to live with some of that because the fact is only one water surface per cell now razmapper is doing a sloping water service through here let me make sure i have that turned on correctly yeah i do but there's only much that can so much it can do if the cells are too large okay now is that going to affect this answer in here though okay let's let's get this going further now i got some water in there is that going to really affect my final answer of where the water went to and how high it got inside of here not really okay that that little you know jump across that one cell it's still accounting for water coming into the cell filling and going out so still accounting for travel time it's just not mapping it as nicely for that overland flow across that steep terrain as you might like as what really occurs in real life but the only way to get that would be to use really small cells and if you start going at that level you're going to have models with just tremendously large number of cells and take forever to run you're not going to get that much more benefit out of the final answer so it's a plus and minus type of thing you've got to weigh the benefits to the you know how much extra computational time is going to take for that benefit okay we can also look at velocities i'm not going to look at a lot of output there's going to be a whole lecture on output but here's velocities in 2d i'm going to turn off the the geometry okay and we can see we can look at velocities and i'm going to turn on water surface and we can get water surfaces i can turn on the particle tracing uh wait you can't turn on particle tracing with max values so you got to have like a that and then i can speed up the particle tracing i like turning on the particle tracing with velocity and again you can't turn on particle tracing at max because max is kind of the max velocity that occurred everywhere regardless of time it's not an actual instant in time so you can't do particle tracing it's less it's an actual instant in time otherwise the tracing won't be correct that's why we don't allow it for we're plotting maximums

Channel: HEC RAS

Views: 29,659

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Id: EYsNHXjPmMk

Length: 31min 7sec (1867 seconds)

Published: Tue Nov 02 2021