Episode 28: 2D Bridges - Best Practices/Potential Pitfalls

[Music] welcome to full momentum in HC Raz podcast I'm your host Ben KY here joining me as always Chris gadell Chris welcome to episode 28 of this podcast series we got some really exciting topics today we're going to have an opportunity to answer some some user questions from folks that follow the vodcast um a lot of cool stuff and then on top of all that we got the NCA tournament that's starting this week you just got some exciting news on your house that you're building lot of lot of good good vibes right now in the HC Raz uh full momentum world I think the best thing though is the weather has been unbelievable the last few days I mean for March mid-march here in uh Western Oregon holy cow I mean mid 70s sunny I mean it can't get any better yeah it's it's a it's it's really good weather but I was it's interesting I was talking to a cooworker today who who is doing planning on some doing some field work in Alaska in the next couple months and their timelines for getting field work done are getting moved up significantly um because a lot of the snow melt and and Glacier melt that's going to be occurring which normally happens in April May is already starting because of that same warm front so um interesting impacts in the uh Water Resources World here on the on the west coast of the United States yeah yeah definitely um it's it's nice so you mentioned my property the the weather um is drying things out up there which is really good because right now uh we're on building or getting ready to build a house up there it's too muddy to do anything but one thing that they could do and we did this last week was drill my well so you know this is it's sort of water related so I thought we could talk about it here but um yeah I had a a a well driller come out and they got this huge drill rig um it elevates a tower up it's like I don't know 40t high or something crazy like that and uh they just got a bunch of these pipes they call them sticks that they uh thread together and they just start drilling it's amazing how fast they go through even solid Basalt um talking like 20 feet would take them about 5 to seven minutes to get through and you know all the while it's just spitting out all of this sludge and and rock chips all over the place makes some really good gravel but the good news is we actually did hit water and there's always a risk you're not going to although I think the risk was pretty low on my site but always a risk you won't get it but we got 55 gallons per minute at 406 feet deep which is pretty good and I'll take that it's G to give us lots of water I got no even semblance of an idea of whether 406 feet is deep for it seems pretty deep for what but is that is that normal is that is that shallow what's what's well it it was shallower than they expected or they budgeted or um estimated for and and that's all based on all the different wells around the area and he's he's drilled most of them and so he looks at all these different Wells and well logs and goes okay well just kind of seeing what the trend looks like I'm guessing you're probably going to be 460 ft and it was just 406 so that's cool saves us a little bit of money and we actually got more water than he expected too he was thinking maybe around 40 gallons per minute so um if you're trying to kind of visualize how much discharg that is um just think of a 55 gallon drum and filling that up in one minute and that's what we got so that's pretty good yeah yeah very nice so tournament time's coming up huh Ben yeah tournament starts this Thursday um I will be taking Thursday and Friday off work uh it's my ual annual uh mini vacation that I take every March uh to watch basketball and obviously it should be should be a good time we have our our uh our company little office pool that we do we fill out brackets so it's a it's a fun time of year as a sports fan for sure what's the what's the best you've ever done in the office pool oh that's a good question um probably like third I don't I don't think I've ever won um but yeah um I was I was I think last year was my best chance to win at Klein Schmid anyway you know I've been doing these for a long time but um and I was looking like oh there's a shot I could win this thing and then I can't even remember what it was but a few very important teams lost in my bracket and I went down I think I probably got somewhere in the 10th Place range ultimately but I was right there I was thinking oh I might I might have a shot here to win this yeah well you know you just got to survive the first weekend um my father-in-law always says uh you can never win your bracket pool on the first weekend but you can definitely lose it on the first weekend so true if you follow out brackets I hope you enjoy watching basketball this week um but we got some exciting Raz content to get to so let's go ahead and jump in that um before we do I just want to give a quick shout out to our sponsor um we're thankful to be sponsored by our engineering firm that you and I both work for Chris kenman Associates who is known throughout the industry as a firm that provides practical solutions to complex problems affecting energy water and the environment you can learn more at clmg group.com um one of the things that you can learn at kmg group.com is about upcoming classes that Chris and I have um we just finished last week our 2024 spring 1D 2D HC Raz course it's a six-week course went really well I think we had almost 40 people um that attended it it was a great size uh really really good class I I enjoyed it quite a bit um our next online class if you're interested in in taking it will be um hosted again online over the course of six weeks one day a week we do lectures and then we have workshops in between um and that's going to run from October 9th to November 13th so it's going to be a fall class um so if you're interested definitely visit kinmit group.com and you should be able to find the link to to sign up for more information and eventually the actual the class itself in addition to the online class we also have finalized dates for our imperson class this year which is going to be in Atlanta Georgia uh from September 10th to the 12th um so that's a 3-day course it's a little bit more intensive so instead of spreading it out over six weeks we do three days of eight hours a day all at one location it's in person so it's a it's a fun way to interact um we get usually a lot more questions and things like that Atlanta is a great location we're really excited to go down there and um it's been a while since I don't think I've ever taught down there you have but it's been a few years right Chris wait so when is this again what month September 10th to the 12th September okay so we're not like Midsummer but it's probably still G to be pretty hot there but uh I I promise you we'll be in an air conditioned location we won't do we won't do outdoor classrooms for that for that class yeah yeah but Atlanta's great uh Atlanta's awesome it's got a really cool downtown area and a lot of good restaurant options and it's just a good walking around place so I love I probably taught I don't know uh I don't think this is an exaggeration but probably six or seven classes in Atlanta yeah um so yeah okay and um for those that are interested uh we don't have the exact location where the class will be held picked out yet we'll have that information soon and we'll certainly share that with you all once we have that um it probably is going to be in the G enal vicinity of where Georgia Tech is at um again not necessarily on the campus of Georgia Tech but in that area of Atlanta I know Atlanta is obviously a very large city so if you're kind of picking out generally trying to understand where that might be that's that's probably where we're going to end up so again more information will will come out and we'll definitely share that with you all as soon as we have it there's also an outside chance knock on wood that we will be hosting uh our annual HC Raz Pub and Grub following that class that has not been finalized yet I do want to tease that out though um because if we get enough people that sign up for the Atlanta class that might open up our opportunity to to host that event which we've really enjoyed that the last couple years yeah sample some Atlanta crap Brew huh yeah exactly that'd be fun yeah cool cool and then just a couple other notes here um a reminder of some conferences that Chris and I will be at uh in the next couple months so Chris is going to be at ussd from April 22nd to the 2 6th so if you're in Seattle um during that time definitely go by the clment booth and find Chris he'd love to chat with you about Raz or or anything else um and then I will also be at asfpm uh which is the uh American Society of flood plane managers um and that conference is held in Salt Lake City this year from June 23rd to the 27th um so come find me there I'll be giving a presentation um on some lowf flow modeling in an aid climate in eastern Oregon so Raz related it'll be it'll be a cool topic um any other news and notes Chris around upcoming events or things to know I think you got it covered although I'm looking forward to our trip to Boston we Ben and I are going to Boston next month and uh that ought to be a really good time um you I mean we we both went to Boston a few years ago right but it was just like a quick drive-thru kind of thing so we'll have some opportunity to explore a little bit and uh I've got family back there too so it's always good to get back to Massachusetts and see that very historic City really cool downtown area and um yeah so it'll be fun very cool awesome well to start off the technical discussion today I want to go back in time and uh engage with some of the listeners that provided some questions for us um we appreciate everybody that submitted their questions on LinkedIn and on YouTube um we are going to try to do a better job of monitoring the questions that come in from that and picking out ones that we think make sense to try to answer on this on this podcast there are some great questions that were on there that were probably a little bit more intensive in terms of what it require to answer that on a on a podcast um but still we we saw those keep them coming and we'll we'll try to pick out ones to to answer next month um on that podcast episode so this week's question that we're going to answer is from Ayan from Romania and they ask is it possible to use the raster calculator function in Ras mapper to calculate at what time the maximum flow reaches a specific location in a 2d model uh this is a great question Chris and I had a chance to kind of talk about it a little bit before the podcast and we think we have some some good insight to share with you all um for many folks that listened to that question or heard that question you might might be thinking right off the bat well there's an arrival time map in Ras mapper why don't we just use the arrival time map and Chris I'm going to go ahead and pull up Ras mapper on my screen to share some things but while I'm doing that if you want to talk a little bit about why the arrival time map wouldn't be able to answer the question that iy had here yeah so specifically Yana talked about maximum flow right and the arrival time map tracks water surface elevation or depth is another way to look at it and so you set up an arrival time map very easily Ben's going to show how to do this and uh you can even specify not just when water first arrives but when it gets to a certain depth at a certain location um but that's again based on water surface elevation or depth not flow um so there is no direct way to get a arrival time map based on flow or even maximum flow which was the specific question here however you can get an arrival time very quickly uh arrival time map very quickly for depth and including a maximum depth which is the one right below rival time so you have a rival time and a Ral time Max now that's not going to technically be the same as your arrival time for maximum flow although as long as there's no significant Backwater through the system it might be or probably is going to be very close close to the same yeah so let me go ahead this this simulation that I have pulled up here is a it's actually a dam breach analysis so it's a good one to use um if I scroll back to the start of the simulation you're going to see that we actually start with with water um in our main Channel at the beginning of our simulation uh and then during the course of this simulation we have the dam breach actually occurs the flood wave moves from left to right so from Upstream to Downstream on the screen and you can see that that that flood W pass through so I a qu I's question was hey if there's a location for instance where we have maybe these cross-sections drawn in here is there a way for me to tell what my ma at what point my maximum flow occurs at this at this location there's a couple different ways to do this so let's start with the simplest way if you're only interested in the peak flow at a specific crosssection in your 2D area you can extract that using a profile line which is which can be added here under features profile lines allow you to Monitor and observe um information either terrain or output information across a line you draw inside of a 2d area if you rightclick on that profile line you see there's a lot of different options here what we're going to end up doing is plotting our time series and plotting our flow time series across this line it's going to go ahead and generate a flow hydrograph based on the results underneath this line and then it's going to display what that is um so you can see here this is actually upside down because I drew it believe I drew it right to left from right to left yeah but regardless this is still helpful to help us understand when the peak of the flow arrives at this particular location so you can see at the beginning uh of the simulation we got about a little under a th CFS that's our base flow condition then that we got a probably like a 100y year or pmf flow hydrograph which is starting to really increase the flow significantly and then we have that that breach right which put things over the top and if we if we scroll our Mouse down to the very peak of this uh flow hydrog graph you can see that the time where the peak occurs is January 4th 1999 at 2:30 p.m. so if you were able to take 2:30 p.m minus whenever the simulation started that gives you kind of the time of arrival of the peak flow at this particular location that's the simplest way to do things but that only works for one location if you wanted that for multiple locations you'd have to draw multiple profile lines and it could be kind of a pain um what Chris what Chris noted there is the uh arrival time maximum map which is going to give us a solution to this question in many circumstances but not all and Chris I'll go ahead and add this map in and if you want to maybe shed some light on when this map would not give us uh the information that that the user was interested in for this particular situation yeah so again arrival time Max is going to be based on a water level um in this case the maximum water level when does the maximum water water level happen uh during the simulation and it attracts it from whatever the um starting time is and you can either set that to this to the beginning of your simulation or some specific time during the event maybe you pick out when the breach begins uh if it's a breach model so um as far as getting Max flow I mean you like I said before you could use this uh arrival time Max as a way to get a pretty good idea of when Max flow gets there uh and it might be very accurate as you know in areas where you don't have a lot of Backwater but in areas of Backwater Max flow and Max stage do not necessarily correspond together at the same time there may be a little bit of offset there um so just be careful with that but if you're just looking for a you know quick ballpark idea about how long flow will take to peek out at some location Downstream then pull open that arrival time Max map and just uh understand what you're getting there you're not getting Max flow you're getting max depth um but that could probably give you a lot of good information yeah and just to review how you add that map so you can right click under any plan once you run that plan so you can see I'm under results I have a couple different plans here that I've ran I'm going to look at our 250t cell plan right click create a new result map layer pop open our hydraulic map type and scroll down to arrival time you can see we have our arrival time which is going to be more helpful for like Levy breach analysis where we're starting off an area dry and then there's a flood wave arriving um but for a kind of a map showing when the maximum stage or the maximum Water Service elevation occurs click on this arrival time Max go ahead and add that map in um and then what I always like to do is right click on that map go to the layer properties and click on this update Legend with View and what that's going to do is it's going to scale uh the output here based on my current view so right now the arrival times are from from 58 hours to 119 hours is is kind of the the possible range of of peak stage for for this particular scenario if I zoom into this cross-section which we were interested in before you can see that all these rival times are very close together which you would expect because there's a a damn breach wave going through that's going to move through pretty quickly and you can see at this location the arrival time or when the peak of my stage is reached is right around 74 and a half hours um after the start of the simulation and you can get this information not only at this location but anywhere in time and space along the center line of my River channel here so I think that answered the question that was was posted there so thank you for for asking and um certainly keep questions coming we'd love to answer additional questions that come in that we can you know answer in a few minutes on on this sort of forum yeah or even even on this particular question if some of you out there have a better way or an alternative way of figuring this out uh share it with us we'd like to share it with everybody else um there's like a lot of things in hecz there are many different ways to get to the same answer so yeah pass along your your knowledge as well so yeah good question though absolutely cool um and we will try to if there are updates to the question or if there are additional ideas or or methods that folks use to answer the the question that that we just went through we'll try to share that on the next podc podcast to keep this kind of as a rolling rolling rolling learning opportunity all right uh next topic is Some Water Resource related news uh specifically in the HC Raz Arena um and that is the new HC Raz 6.5 version 6.5 was released a few weeks ago and uh know very very excited about that was reading through the release notes and the new features uh that are included as well as some of the bugs that were fixed from the previous version and it sounds like there's some really interesting things particularly on the sediment transport side of things so I know St and and his team have been working really hard to improve the functionality of of 2D sement transport if you're using that function quite a bit there sounds like there's some some really interesting features we're not going to touch on those today um but we did want to mention a few that stood out Chris to you as you were looking through the release notes so I'll turn it over to you to kind of talk through what those are yeah let me get my screen uh shared up here and the first one I want to talk about and we'll get to the others here in just a second uh but the first one I want to talk about is this new compare Model results or new compare model data feature this is something I've been wanting for a very long time and they finally put it in here uh I'm still learning it myself but I want to give you some of the highlights if you go to file on the main Raz window go down to model um compare model data it'll bring up a window like this and what you're going to see here are all of your input files kind of linked together so we have our plan files here the second column over we have flow files to the left geometry files to the right and then over uh on the far right are our terrains and you can see how lines kind of connect everything up so you can quickly go through and go okay for plan four what are my flow files or my flow file that goes with it my geometry file and you can see there's it's connected with G13 and u01 um and you can even figure out okay well what terrain does that geometry go with what's it associated with and it points to uh the terrain so that's kind of helpful but there are other things you can do here as well okay so let's say that we want to uh compare different plans and what what are in those different plans uh maybe you're interested in the equation set that's used and you want to make sure that all of your plans are using the same equation set or maybe a certain coefficient or maybe your Theta value whatever the case may be you can quickly compare plans either a handful of them or all of them and you just would click right click and say add to list here and that puts a tab at the top right click the next one add to list uh and I'm just going to add now some of these are not enabled because they haven't been run yet in my particular um instance of this project this is the Bald Eagle Creek one by the way so I'm going to add let's just add three from now but you can add as many as you want and then once you've added these plans now we can go to plan the plan tab up here on the left and it's going to give you General plan information like the title of the three different plans the plan name some basic stuff here's this is interesting you can if you want to verify that the time step is what you think it should be for each of these plans you can double check on that but what I was getting at before are the plan parameters so I can click on plan plan parameters here and I can see okay what are the things that are different in these plans now the equation set that I mentioned earlier is not listed here the reason it's not listed is because it's the same so it's only listing the differences but I can have it check I can check all and then I can see everything down here not just what's different but everything and so if I uh let's see where is that uh equation set um why am I not seeing that in here well yeah is it under 2D floor areas Chris okay thought it might be I know it's somewhere because you and I have both looked at it yeah we looked at it before I don't know why it's not showing up but anyway you can see there's what if you what if you go to flow flow oh yeah it's just the flow file okay but yeah so um anyway you can see a bunch of other things in here too like um you know your max iterations water surface tolerance uh a lot of 1D 2D stuff how many warm-up time steps that you have set um getting into 1D things like the friction slope method that's used what gravity value is used uh I don't know if you knew this B but you can change gravity in hecr that's pretty cool um so quick way to compare different things um we can do the same thing with geometry files now I don't have any geometry files selected so let's let's see if we can add those let's just add a couple then I go into the geometry tab up here compute geometry differences so it's looking through both of the input files and it's going to show you the differences between them that's cool yeah yeah and there's even graphical represent presentations of of different things as well so it's really cool as you can tell Ben I'm still learning this myself so here's a nice nice little plot of the difference in N values right uh in the in the data set and so this is a spatial map showing me where do I have differences in N values okay anywhere it's kind of this gray color that you see over here in the legend that means there's no difference okay blue means a negative difference and orange means a positive difference so you can quickly see how geometry changes spatially in your model as well so really powerful stuff I'm I'm eager to continue to learn this and use this I want to use this for reviewing models a lot uh because this is you know this is something I do a lot in our company and you do too Ben that we review other people's models and one thing that I like to check is that hey are you using the right parameter or the right equation set or you're you've got consistency between plans of say the time step you're using this is a quick way to do this uh rather than having to open up one plan look for all this stuff close that plan open another one look for the same thing over and over again so yeah so outside of because qqc obviously is the one that is obvious in terms of what this was probably created for and where it's going to be most helpful can you think of anything else Chris put you spot here a little bit where this could be useful yeah I mean even for your own self- review you know once you start getting to 10 20 30 or more plans it's really hard to keep track of everything and it takes a long time to verify every plan has the same whatever uh or that you have consistency and so this would just be a very quick way even for your own model just to verify hey you know everything looking correct is any surprises in here so um I think self- review I think uh independent review are two very important reasons um or benefits for having this thing so uh there's probably other things as well um but those are the two that come to mind off the top my head good awesome well yeah that's a great feature looking forward to give getting more familiar with it and building it into our standard operating procedures when it comes to to reviewing reviewing models like like you said Chris um yeah there was there was I said there was a number of updates we really could do probably multiple hours going through all of the different features that have been added but we picked this one as well as the next one which is going to lead really nicely into our our topic for today um the primary topic for today that we're going to discuss is is 2D Bridges best practices and potential pitfalls but the update uh related to 2D Bridges um that that came in version 6.5 I think is worth touching on so Chris you want to talk a little bit about what what that what those changes were yeah so I'll talk real quick about what the changes are then I want to give a little bit of um history on 2D Bridges and get into some best practice here best best practices so the changes that are most important here is that you have an automatic skewing option now for 2D Bridges so if I go open up um a bridge let's this is the Bal Eagle Creek data set the one I always like to show people because it's got everything in it it comes with the software um really good stuff but you can see that this particular plan in the Bal Bald Eagle Creek the one that says single 2D area with Bridges feq um that's the one that you want you want to look at if you're interested in seeing how bridges are done but there's several bridges in here you can kind of see a lot of these are labeled here but I'm going to zoom in because there's one in particular down down here that's really skewed okay um let's look at this Highway 220 Bridge let's zoom in there yeah I'm looking in the geometry window uh you can see this in Ras mapper as well but um when you edit this bridge if I go to edit connection left click on it edit connection you see the um sa 2D connection editor and that's what we use for 2D Bridges by the way but under options now you can see that is a skew bridge data option that's been added in 6.5 click on that and it allows you to skew it from 45 to 45° uh positive being a clockwise rotation of the bridge negative being a counterclockwise so if I look at this bridge if it was UNSC skewed it would be like this so this one is a counterclockwise rotation so I would give it probably something like4 5 degrees it's a pretty extreme skew here now why do we want to skew it well because in 2D Bridges we are using the bridge curves right I'll get into the bridge curves here in a second if you don't skew this bridge then Raz is going to think it has more capacity to pass flow than it actually does because it's going to think this width from here to here is the actual hydraulic width of the bridge when in reality the hydraulic with is more like this all right so you want to skew this up until this new feature was added in you'd have to skew it manually and in fact skewing it manually caused some problems in earlier versions uh 641 even that it would artificially block part of the channel if you manually skewed it it was kind of a weird thing um a bug in the software but um they were aware of that and so they fixed it by putting this skew option in there so if you have skewed Bridges definitely get into version 6.5 make sure you skew it there and then you're going to have a much better result Ben and I worked on a project recently um where we had a lot of 2D Bridges and several of them were skewed yeah and um it caused a lot of problems it did um without having the skewing option in here so glad that they added that in there awesome yeah looking forward to being able to use that as opposed to the kind of the Jer rig approach that we came up with to make it work which is yeah yeah so let's um let's step back a little bit Ben um and here's a trivia question for you okay okay we like to do trivia every every episode and um I've got one for you Ben and that is what version of hecz did 2D Bridges um were 2D Bridges at it in what version yeah um I I believe it was 6.4 am I correct you got the first number right it was 6.0 yeah yeah 6.0 introduced introduced bridges into 2D areas but here's the funny thing is uh we had 2D areas all the way back to version five so we've had we've had 2D modeling in hecr B if you can believe it since 2014 2014 way back when you were in what middle school or something or the year year before I started working okay okay you're still a gonzago um on campus watching every single basketball game in person right um and and uh 2D 2D modeling was introduced but it didn't have bridges in it in in the 2D areas and so um it was a little bit difficult if you were trying to model a river in 2D and you had some bridges you kind of had to get creative uh you know either you just didn't model the bridge or I even saw some people would insert little um short 1D reaches you know between 2D areas just for the bridge uh but it was kind of not it was not great um there's a lot of getting creative that had to be done to to get around not having 2D Bridges so it was really nice when they added that the best approach I remember seeing was you know if if you could kind of coding the bridge in as a covert opening right yeah yep people were doing that uh or as a gate that's another way to do it um but of course then you were using Culver equations or gate equations not Bridge equations um and then you sometimes you got really lucky and you had that model that had a bridge and you're like oh no you know what are we gonna do with this bridge and then you realize oh the water doesn't touch the deck yeah the water doesn't touch the deck and so we don't actually need to include a bridge here we have the abutments and the roadway embankments as part of the terrain and then just we didn't put a bridge in at all and just modeled it fully 2D and it worked great but that was only if the water didn't touch the bridge deck so anyway fast forward to version 6 2D Bridges were added and now we're at version 6.5 and we've got skewing added to 2D Bridges but I want to show you a little bit about uh best practices for 2D Bridges since we're on that topic so as you uh as you know Ben and a lot of our listeners know uh with 2D Bridges we end up with these I don't know what they're technically called but these temporary cross-sections yeah uh sometimes they call them dummy cross-sections or bounding cross-section bounding cross-sections yeah whatever you want to call them but Raz uses these temporary cross-sections here to BR to build a family of rating curves for this bridge and the family of rating curves are based on the exact same methods used for 1D unsteady flow for bridge curves so if you've ever done any 1D unsteady flow modeling you know that Bridges have these htab curves that go with them okay and this is just pre-processing the geometry of the bridge into a family of rating curves that way when you run the model instead of having to recompute the Headwater tail water flow relationship you're just picking those values off of a pre-developed table and it makes the model run way faster so they decided to use the same technique for 2D Bridges develop these rating curves this Headwater tailwater discharge relationship but instead of using the 1D solution use those rating curves to include an additional Force term in the momentum equation for the 2D equations or the 2D simulation so every single cell face that runs down this Center Line has a pair of cells associated with it a Headwater side and a tailwater side Headwater tail water right so Raz will take those family of Curves and it will convert that into an added Force term that's applied at each of these faces okay and then it just runs the 2D equations just like it normally would it just has that additional Force term that was taken from the rating curves so what you have to do is you have to develop those rating curves and that's what these dummy or temporary cross-section are all about because you need these four sections to build those family of rating curves and so Raz does that for you you just have to specify where these sections go relative to your bridge and then um when you hit compute Raz will pre-process that into um the family of Curves now there is some stuff you have to do a front to get this to work right first of all locating these cross-sections if you go to the uh connection editor here and get into the deck and roadway editor you'll see there's a distance value and a width value so the width value is the width of the bridge deck at the top of the bridge the distance value is the distance from the edge of the bridge to these bounding sections so what should we use for these values well width is pretty easy right it's just the width of the bridge that's a physical thing you can measure but what what do you think think Ben about the distance value what should we use for that yeah I would say if there is like an embankment um on either side uh of our Bridge um so on the left River left or the river right side of of our bridge opening I would be tempted to put those cross-sections at the toe of of the embankment on either side but what what do you think Chris that's exactly right and you can kind of see the roadway embankment here M um you can see this cross-section is not at the toe it's on the embankment so what does that mean well this embankment is actually going to influence the uh the cross-section in the family of Curves and we don't want that to happen so it's better to have these better to push them out so that they're both um you know at the toe or a little bit beyond and so you might want to increase this distance If This Were My model so that this one pushes out more to the toe okay but you you don't want to go too far way right because these crosssections are supposed to represent what's happening at the bridge so if we push this way down stream here well that's totally different geometry than what's happening at the bridge and maybe I'll let me move to a different Bridge because it's hard to describe this with a skewed Bridge so I'm going to go to one of these other Bridges here like uh let's do this railroad bridge how about this is another bridge this is the great thing about the Bald Eagle Creek data set is there's a lot of things you can look at and test out and verify okay so here we can see and by the way this purple this is just the 2D area Manning's region so I'm going to turn that off because we don't really care about that right now um okay so now we can actually see the the channel here and you can sort of see the embankments the terrain is not very good in this part of the model but you can sort of see where the where the toe is so you would push that out right but you definitely do want to have it um as close as possible just not you know up on the embankment itself now so Chris one question I I think people probably are thinking right now that our nud Tod Bridges is you know we're when we draw in our cross-sections for Wy Bridges we're taught that we want those bounding cross-sections to kind of be at the the Terminus of the expansion and the contraction a flow that moves through that bridge um so they're going to be quite a bit further out than the bridge that we have here is there a reason why those cross-sections aren't kind of matching the typical placement of those bounding cross-sections for 1D yeah that's a great question Ben and that's because we don't care about contraction and expansion in 2D models well I shouldn't say we don't care we don't care the same way we do in 1D because for a 1D model we would have another cross-section up here where contraction starts to begin yeah you know out here in the flood plane and we'd have another one down here somewhere where expansion has you know completed right but we've got our 2D area here to solve that for us so we don't care about that in a 2d model that's done for us with the the 2D equations because we're capturing flow in multiple directions we're capturing contraction and expansion one of the cool things about a 2d model is you can actually use the 2D Model results to figure out your contraction and expansion reaches for a 1D model um of that bridge if you were so inclined to do that so in this case you know if you think of the four cross-section setup that we've you know we do for 1D where you have cross-section one down here where it's expanded cross-section two here three here and four up here we don't need cross-sections one and four we just need cross-sections two and three plus the two internal cross-sections that's all we need yeah but now that's not to say if there's still little bit more contraction or expansion from the bounding sections to the bridge itself that we shouldn't include that and you definitely should and in fact if you go into the bridge editor you can see under options there is a spot for bridge in effective areas now this particular Bridge we wouldn't need it right because the bridge there no abutments that are projecting into the water causing a contraction between the bounding section and the bridge section itself there may be some in here somewhere let's see if we this one has a little bit you know so you might put a little ineffective flow right there okay you only you only need to include those ineffective boundaries if it's if the physical blockage that's causing that ineffective area is not included in the terrain correct if it's including the terrain that's going to be picked up by the 2D equations yeah so let's say on this particular particular Bridge let's say I'm I extended this bridge out here onto these roadway embankments now all of a sudden I have roadway embankments as part of my bridge geometry and you're going to see on the sides of this a complete blockage right where these roadway embankments are okay and that means that the see this is the Upstream inside that means the Upstream bounding should have some ineffective flows there because water will be contracting okay as it approaches the bridge section there'll be a little portion of this bounding section here let me zoom in on it oh what happened here let's get back there there's going to be a little portion you know o let me Zoom back out a little bit let's say this bridge extended onto the embankment there's going to be a portion of this section that should be ineffective because water over here will not be moving in the downstream Direction it's going to be ponding it's going to be contracting to go through this opening okay so that would require some ineffective flows and that gets to another best practice here by the way Ben and that is when you're doing a 2d Bridge it's best to just include the free span portion of the bridge notice here we just have the deck here we don't have the abutments included okay leave that to the 2D area like you see over here and over here just put in the free span then you don't really have to worry about ineffective flows number one plus number two if water goes over these embankments you have the benefit of the 2D equations being used okay instead of wrapping that in as part of the bridge yeah now if I look at the shape of the cross-section in the view that you're looking at right now on River left it looks like that a butman is included in this in this bridge I mean you can see the the increase in the train elevation that goes up and above the bridge so is a little bit in theory technically you should put an effective flow area in the bounding cross-section Upstream of that to account for what you're saying there right in theory yeah in theory a little bit and you know it's maybe a judgment call if you need that much but it it really depends to where this section is located this one you can see is a little bit on the embankment just like this one is so I think some of that's going to be picked up here as well okay let's look at the same thing on the downstream side that's the next Bridge sorry I was moving Bridges not moving um okay so here's our bounding section right and it looks like yeah it doesn't go up as high if I go back uh to the interior this gets up to like 575 okay which is way up here so yeah I might want to put just a little bit ineffective flow here to account for that for that bit so that's that's a good eye Bend or or narrow the width of the bridge deck right so that it's it's only covering kind of the span yeah yep yep exactly so it's really up to you you know do you think you need to have you know this kind of blocked out on the previous and yeah I guess the question is yes or the answer is yes a little bit uh not a whole lot okay so think about expansions and contractions uh from these bounding sections to the bridge section itself and use that to inform where you're going to put your ineffective flows around there so what else do we have there's contraction and expansion coefficients okay those are even though we think of that as being a 1D thing those are actually used in the bridge curves and so click on that and you can change to something different the defaults are what the manual recommends we use for Bridges and so that's what they're going to use but if maybe this is a very extreme contraction an expansion Bridge a very small opening relative to the full Channel width then you might bump these up a little bit but generally speaking most bridges you're just going to keep the defaults for those now the other thing that's um important and is a little bit different I mean you can see if you're used to ond Bridges a lot of this stuff is the same right but you do have to get into these bounding sections okay under options you would just go let me just show you again real quick under options go to external and internal Bridge cross-sections okay here we see the four cross-sections that you see in the schematic on the left here they're listed out in tabular form and they're going to show you the station elevation points under these cross-sections u based on the terrain underneath as well as the left and right Bank stations and the Mannings end value it's going to assign to these cross-sections now all of this is done automatically for you except the Manning Zen you have to put something in here for Manning Zen now you can have just one value at the top and that gets applied to the entire cross-section or you can spatially vary it if you want to by adding in more values here Bank stations oh yeah go ahead is it fair to say that you probably want to use the same Manny's M values that you're using for the rest of your 2D area for the channel segment itself so if you have for instance um a channel specific Manning Zen value in a Manning Zen layer you'd want to make sure that this Manny M value matches whatever you're using for that channel layer so that there's not kind of a contradiction there absolutely yeah I would see okay this cross-section is pretty close to these faces here what are the end values on these faces cell faces that's what I'm going to use here for my NV value for that cross-section uh so yeah usually I mean you're channel will have one end value and you can just adopt that for the entire thing now if you do extend your Bridge which Ben and I don't recommend you do but if you do extend it out onto the roadway embankments then you might have a different end value over there um you know maybe it's forested over there um or maybe there's some pavement who knows but um if you're just keeping your Bridge limited to the free span then you're you're just pretty much just picking up the N value that's in the main Channel there and to do a high level overview on these four cross-sections again so just as a reminder the Upstream outside crosssection is going to be just Upstream of the toe of your embankment the Upstream inside and downstream insides are you can't edit those those are based on the the physical width of your bridge and then the downstream outside is going to be just Downstream of the toe of the embankment correct yep and those two the outside bounding sections are both based on this single value this distance value so they're always going to be the same distance uh upstream and downstream of the bridge deck yeah some people ask me too you might recall this in the class we teach when we get to the bridge lecture uh the bridge topic I'll get a question that's like hey what if um our embankments are vertical there's no slope to them where should we put those bounding sections should be they be like one tenth of a foot upstream and downstream of the bridge deck and uh I you know I don't know if that would cause problems that sounds problematic to me so I always recommend at least go the same amount as the dis the the width of your Bridge just do that same value Upstream of it I think that's a pretty good spacing um but I would not want to put it right next to the bridge deck and honestly I don't know why like I can't tell you what in the computations would give me hesitancy there but it just doesn't feel right I don't know what you think about that Ben well one other thing that I think again folks looking at this and looking at the previous bridge that we were looking at May notice is that the bounding cross-sections appear to be lined up very closely with the cells the Upstream cell faces and the downstream cell faces they're not spot on on this bridge they're really close on the other bridge is there any sort of requirement or recommendation to have though that um upstream and downstream bounding crosssection kind of align to the upstream and downstream cell faces there's no requirement for that um but that gets us to another important part of bridge modeling that um we should talk about and that are that is these bounding cells but I mean just to get to your question no it doesn't have to fall on the face it doesn't have to be outside or inside the face it it's really irrelevant um because these are two separate computations being done you have the family of rating curves that are only done with these cross-sections and then once that's done that's done and that we've got our Force terms and now we can run the 2D equation uh 2D equations and Raz at that point doesn't care about the cross-sections anymore it has the added Force term on these uh cell faces on the center line it's all 2D from there on and so it really doesn't matter if these things line up or not okay yeah uh very common question though people assume hey because we have cell faces there maybe they should line up it doesn't really have to at all okay but there is there can be issues with these bounding cells so another really cool thing that they added to version 6.5 with respect to Bridges is the ability to spread out that Force term over multiple cells through the bridge now this bridge it doesn't really matter because the cells themselves are way wider than the bridge the cells themselves I like that what's that the cell the cells themselves the cells themselves yeah it's hard to say that but let's um let's see I had one that I was messing around with Okay so let's say we have this bridge here and it's it's really wide or we have really small cells or both right and here you can see we've got multiple cells in the direction of flow underneath this bridge that last Bridge we were looking at it just had one cell not even a full cell on either side side of the center line but here we've got multiple cells well previous to version 6.5 Raz would take that Force term and only apply it on the center line faces and so for a bridge like this where you've got you know potentially a lot of energy loss going through the entire bridge that would all be collected together and applied right here at this face or these faces on the center line and so you get a real sudden drop head loss there um Head Drop applied in a very discreet and short location right and thing Ben and I always talk about is Raz doesn't like things to happen drastically right so this situation would cause a lot of Errors it would cause your model really slow down as it's chugging on these errors and so what ATC did for 6.5 is they spread that force over all of the cells underneath the bridge and added it incrementally as you go through the length of the bridge which Smooths things out a lot better and makes it more accurate too in my opinion so that was a really nice um addition for version 6.5 with h respect to Bridges as well very cool what about uh what about peers Chris 2D Bridges and peers are there some best practices or potential pitfalls that people need to look for when they're putting peers into their model yeah so this another really common question we get Ben and I get are um what's the best way to model the here well I'll tell you one thing you don't want to do if you if you put in a bridge let's go look at um some of our s2d connection Bridges you can see we have some peers here right that's the railroad bridge we were looking at earlier so a lot of peers in here um let's say for this one we put these four peers in in the bridge editor if we did this we would not want to add those in as part of the terrain and that's the other way to simulate a bridge so you wouldn't want to do both in the bridge editor and as part of your terrain you want to pick one or the other uh if you do both then you're going to be double counting the uh the losses associated with these peers so option one is to make them part of your Bridge geometry using this pier button right here really easy to add peers in you just go to the pier button you add in one perer at a time from the bottom up using this peer width elevation relationship okay and you've got some peers really easy to do okay um this is great for Bridges where the bridge happens to be in your modeling domain you want to make sure you're kind of capturing the um the backwat effects of that bridge um the the flood risk due to that bridge um you know how it might change overall the the flow patterns or the the velocity as it approaches and leaves the bridge site that's great now what if we were actually simulating the Hydraulics around one of those peers okay let me Zoom back into this new bridge let's say for example and let's say we've got one Pier right in the middle here and the focus of our study is to get the Hydraulics around that Pier so we can do a scour analysis let's say or we just want to get the Hydraulics really refined around that Pier that is the focus of our study maybe we want to do some force computations on it uh for design okay I would rather put that in as part of the terrain than as part of the bridge geometry there and so if you go into your um into Ras mapper to the location of that bridge uh let's see where is that there it is right there I'll zoom in and I can do a Terrain mod on there pretty quick quickly and and easily so I'm going to turn off the structure for now just so that I can see a little bit easier and I'm going to put a pier right here using a Terrain mod so I would just come down to my terrain I've already got modifications included in here for some other things so I'm just going to add a modification right click add modification shapes and let's do a an elongated peer about okay I'll just call it peers but it's going to ask for a name and so now I'm in edit mode already already and I've got my create new feature button turned on I can just come in here and click anywhere I'd like to put an elongated Pier if you look closely it's already got an elongated Pier there but it's too small so I'll have to adjust that but I'm going to stamp it here first and when I do that it's going to ask me for some information okay so yeah I'll replace terrain value I'll make it uh the elevation just really high and I always forget what Bald Eagle Creek is but I'm just going to guess 350 for now I want to rotate it because it's going straight up and down now so I want to make it maybe about let's say 60° rotation see how that does and the width I'm going to make it uh much wider let's make it a big 30 foot wide pier and I'm going to make it uh 60 feet long that's a huge beer yeah it's a it's a big river too um so let's see radius I'll probably want the radius to be like the width as well um on both sides okay let's see what that does okay so there's my pier and zoom in and see where okay I could probably make it longer um maybe uh I'll go back to edit feature click on this and I can just graphically move this in theory yeah I don't think you can I've never seen G gives us the handles but nevertheless I can edit it if I right click on it and maybe I'll make uh the rotation a little bit more so it's more aligned with the direction flow so let's see if 65 does it and then I'm going to make it uh I'll make it 100 feet long real monster Pier here okay that looks better and um when I hit apply in theory oh no it's only going to let me stamp um after I've made the change here so what was it 65 okay okay so now if I want to add more I can just start stamping them like this okay uh but I said I was only going to make the one so we'll just do that so I'll come back in here to edit feature and I'm going to delete that one delete that one delete those two okay so now I've got a pier here of course I would want to have much smaller cells around this right and probably some break lines too don't you think Ben yep yeah going to be pretty important to make sure that your cells are small enough to capture those effects otherwise you're kind of tricking yourself into what you can really represent with that yeah yeah so I would probably put a brake line because I I would want to face on the edge here so I'd put it probably oops just inside I didn't draw that very well but I'll edit it it's just inside there and then I'll do another one do another one like this just inside okay and then um maybe I'll make the um cells much smaller around this so let's make them probably even once smaller than that that but uh well let's start with 5T for both of these then I'm going to highlight them both and enforce okay of course I get some red dots somewhere else and it's now it's conflicting with this brake line that's going across here um which is actually a structure not a brake line so it's going to be tricky so I would have to do the same thing on this one yeah probably be easier to do it as a refinement region yeah you're probably be right yeah so you could do a refinement region but the bottom line is you're going to want to have smaller cells like like maybe not this small but definitely of the order magnitude of the width of the pier or smaller for sure yeah uh in order to get the Hydraulics really good there so just something to consider it's it's a lot of work but you can do peers as part of the terrain as an alternative to to doing them as part of your Bridge good awesome well we've been able to touch on uh you know where to place the center line span for a 2d Bridge talking a little bit about the bridge curves and how the added Force terms actually Incorporated talking about where those bound bounding crosssections should be placed and when you need to add in effective flow areas in place and when you don't need to add in effective flow areas a little bit about Piers um was there anything else Chris that you thought was worth sharing for folks just around best practices and potential pitfalls obviously there's a lot more to discuss with 2D Bridges overall but um anything on those two topics particular I'll I'll leave you with one more thing on uh 2D bridges in particular small is not necessarily better for a 2d Bridge um you know if you a lot of times the the tendency is to hey I'm getting some errors let's make some smaller cells here um not always going to improve in fact might make those errors even worse what I found is that uh it's hard to do this on a skewed Bridge so let me go to a different one I'm going to go to one up here uh that's not so skewed let's get rid of these computation points harder to see um okay okay so here's a good one here not very skewed um but what I found is you want to have I mean you still want to have good resolution across the channel so you know kind of minimum five cells maybe minimum six or seven somewhere in that range but you do want bigger cells so you can elongate them and so one thing that I'll do here you can kind of see that these are sort of elongated but that's just coincidental but I'll come in here and I'll uh um turn on the computation points a lot of times and I will do something like this I'll uh let's get into edit mode computation points and I'm going to delete these oops that's not what I wanted to do I want to select yeah so I'm going to delete these like this now you can see I've got another geometry on somewhere else so I'll make sure I turn that off here in a second okay where's that other geometry it's probably in the results yeah um no it's test Bridge it's the last geometry in the layer oh yep you're right there it is okay so then what I'll do is I'll take these cells here like this ah not delete them H hold the control key so you can select multiples got to have a really fine touch on your mouse to get these little points here and these are hard to see come on there we go okay so now I've got them all selected I'll just drag them down like this try to keep them in the same alignment okay because what we want to do is preserve the um the brake line here um what did I do oh yeah I'm gonna have to get rid of these too yeah so then you get rid of them on this side as well and then you end up with really long skinny cells right so I'm not going to take the time to get rid of these but you would do the exact same thing on the other side and now you've got long skinny cells right and that's going to give you more surface area which is going to give you more volume per cell but we still have the lateral resolution that we need to capture the Hydraulics um and the velocity distribution across the channel okay and by having these larger cells here it better absorbs flow coming from Upstream to Downstream and minimizes those nuisance errors that can really slow down your model um just something that I found over doing Bridges a whole bunch of times that sometimes helps and this would be specifically for if Bridges were being included in a model where obviously any of the results inside or near the bridge were not an area of Interest so not doing scour analysis not doing any sort of detailed analysis of of flow stage or velocity inside of the bridge because if that was the case you'd certainly want to do the opposite of this you'd want to make a lot of refinement inside of that area to really get a good distribution of velocities and whatnot yep yep and then it's a totally different model right it's it's a nearfield model and you'd probably want to cut out the rest of your model and just have a kind of a zoomed in modeling domain and you can use the bigger model to inform the uh boundary conditions of the smaller nearfield model but yeah you're right you're going to have a much different model with much smaller cells in that case yeah and I'll just go back to something that we started this conversation with Chris which is you know the you had said that in in previous versions before 2D Bridges were available you kind of got lucky if the Water Service elevation at your particular bridge wasn't high enough to strike the low cart of the bridge and therefore you didn't need to include it that's still the case right I mean if you have a model with a lot of bridges run the model before you include the bridges to get an idea of generally what the water surface elevation is and what the elevation of the high court is at these locations and if it's not close to the low cord don't go through this all this work to put these in um so that that still holds true you don't need to add brid just because we have the feature available they really need to be added in locations where it's a point of emphasis it's a it's a location that you're really wanting detailed results for or if the water surface elevation that you're modeling um gets high enough to to strike the low cord of the bridge yeah I'm really glad you brought that up because I think personally I think it's better to model it as a 2d with uh area without a bridge if it's not hitting the deck because when you model it as a bridge if it's not hitting the deck it's going to use a low-flow method and Ras either the energy momentum or Yarnell equations either of those are available to you well none of those are going to capture what going on through that bridge better than the 2D equations would for a lowf flow case so yeah just don't put the bridge in at all in that case yeah and uh yeah I think that's that's a a good good point to end this particular discussion on Chris unless there's anything last minute that you wanted to add in no I think that's good um glad to share this with people because um people are doing 2D Bridges more and more and 's a lot of questions that come up we get them all the time in our class um right Ben when we get to that 2D Bridge the questions come flying we get to that lecture right uh everybody's interested and bridges are everywhere over streams so it's uh you're bound to run into one when you uh when you have to do a hecz model whether it's 1D or 2D uh they're kind of hard to avoid they're everywhere yeah you're good all right awesome thanks for talking through that stuff with us Chris um next week uh we will be discussing 1D versus 2D restoration modeling so Raz models are are used for a lot of different types of projects uh more and more you're seeing them used in kind of the restoration space um we have a workshop within our class all about kind of incorporating restoration design using 2D modeling um and we're going to discuss kind of the pros and cons with with using 2D and then also the pros and cons with using 1D to do restoration modeling um because you would think in all situations it's always going to be better to use 2D but um it's not necessarily always the case so we're going to get into that a little bit we're gonna have a a guest on that B that podcast Robert shom who's A A co-worker of ours who's done a lot of restoration modeling both with 1D and 2D and we're going to pick his brain uh on his experiences of which kind of method is appropriate for different objectives within different projects so yeah that would be a lot of fun if you have questions or experiences doing 1D or 2D modeling of of restoration sites or restoration designs definitely leave your experience in the comments let us know how that's gone what you've learned uh any tips and tricks you'd like to share and we'll try to pass those along as best we can if you have other questions that aren't restoration related please leave those in the comments too and like I said we're going to try to do a good job of reviewing those each month and uh replying to the ones that make sense to to answer on on this on this vodcast here that's all I got Chris anything else before we close out I'm wondering Ben when do you think HC is going to put little analog fish in the software for restoration modeling think it'll ever happen well it's gonna they're goingon to need to start incorporating some 3D stuff I think before we get to that point yeah well I mean they're trees in there now so yeah why not yeah so no but that's good yeah um looking forward to the next one I really like doing restoration modeling one of my favorite things to do so it'll be a lot of fun awesome well thanks everybody for joining us today uh we'll see you next month uh this has been full momentum in HC Raz vodcast until next time

Channel: The RAS Solution

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Id: YmLBdOqWiRo

Length: 74min 9sec (4449 seconds)

Published: Thu Mar 21 2024