Spatial Precipitation and Infiltration

hi my name is gary bruner and in this video i'm going to be talking about spatial precipitation and infiltration with hec ras specifically what we're going to cover is how to create the raz map layers you'll need for defining infiltration parameters as well as how you attach gridded precipitation to the encity flow boundary conditions editor and after that we'll look at model results and i'll show you how to plot incremental spatial precipitation as well as cumulative we'll also look at how to create layers for cumulative precipitation cumulative infiltration and cumulative rainfall excess so with that let's get started so here what we're looking at in the geometry editor is our friend baldygoal creek and right now i have a single two dimensional floor area modeling bald eagle creek and i have a traditional upstream boundary cushion for upstream inflow and traditional downstream boundary condition where i got normal depth outflow so what we want to do is we want to add spatial precipitation and infiltration information to this data set so let's start by looking at the layers we're going to need in razmapper so let's open up razmapper and the first thing we need to do in any study is create a land cover data set and we normally have to create that just for n values but we're also going to use that for infiltration information so to create a land cover data set you go over to map layers you right click select create new raz layer and then land cover layer this brings up the land cover layer editor and what we're going to do is we're going to create a base land cover layer out of the usgs national land cover data set so i'm going to go out and grab that i have that stored on my machine so here i have the 2016 national land cover data set for the whole united states but when i open that it's going to only import an extent based on what i choose and right now i have set for the terrain which means it'll create a rectangle around the terrain and it will only import land cover data for that rectangle there are other options such as geometry and terrains current view et cetera et cetera okay the other thing you're going to see is it automatically picked a naming standard based on the national anchor data set of 2016 which gives us this unique classification names of what it found in that data set for this area and then the final output is going to have those names in an id number so let's go ahead and pick a directory to put this in i'm going to i'm going to leave it in this land cover directory but i'm going to give it a name called lan cover test because i already have a land cover dataset i created for this but we're going to create a new one here save and i'm going to go ahead and hit the create now this is going to go pretty quickly because the land cover data is not huge data it's because it's just integer numbers per grid cell to identify what land cover type it is so it's reading the data in and it's writing and creating two files it's going to create a land cover test.tiff and a landcovertest.hdf file and those are the two files that define the land cover data set for raz so it's done and there it is if we zoom in what i want to show you is that when we're on this land cover data set we can see okay we see the different grid cells and we can see what they are one thing i want you to notice is the river so there is an open water land cover classification of the river but notice it's not covered completely the national data sets do not do well at defining stream land covers and we want to define the stream accurately so we can set appropriate infiltration parameters for the stream okay so what you can do now is though even though we've created this land cover data set here we can add additional user-defined polygons called classification polygons and you can either draw those by hand or you can import them from a shape file or you can copy them from another layer now in this case i already have a land cover layer that i created and it does have a classification polygon that i created by hand called main channel so i'm going to start the editing process i'm going to select that layer and then i'm going to go over to the classification polygon layer i'm going to right click and say copy selected features so that just copied into memory that main channel polygon now i'm going to go down to my new land cover data set i'm going to say edit that layer and then i'm going to say paste feature okay i'm going to turn off the old one so we can see there's the new one in our new data set so then i'm going to stop editing and i'm going to say save so now when i look at our new data set i still have all the over bank land cover attributes i previously have it now i have this nice channel one now generally in a real study we probably would create several polygons for the channel because that way we could have different n values for each polygon as well as infiltration properties if necessary but the main reason for multiple polygons is the different n values now the next step is to edit the land cover data table so what's in that land cover data table is manning zenbae is which we which is what we normally use land cover for but also there's this percent impervious adding percent impervious as an option and it depends on how you want to do infiltration modeling in this example we're going to use the scs curve number method for infiltration however i don't like using curve numbers that include the impervious i like separating out the percent impervious from the pervious area and then create curve numbers that are only for the pervious area so i like to put in percent impervious because that way i know for those land covers that have percent impervious that percent of previous is going to have 100 runoff no infiltration and i think that's a more accurate way than lumping impervious area into the curve number okay now rather than enter this by hand i already have a table i created for this same data set from other land cover file so i'm going to just go ahead and copy that and then i'm going to paste it into our new one so i'm going to right click on the layer and say edit land cover table and then i'm going to hit control v and there we have it so what we have now is manning's n values and we can see for our main channel we have a mentioned value of 0.035 and a percent impervious for the main channel the channel of 100 meaning we don't want any infiltration there we want 100 runoff if water is hitting the channel okay and you can see some of the other percent impervious for the different land cover types some are zero but some have a percentage now these are initial estimates of percent impervious so i go to calibrate this model this this is something i might change okay i might change these percentage proofs because maybe my initialism is too high or too low so depending upon if i'm getting too much runoff maybe i have this too high if i'm not getting enough runoff maybe i have it too low okay so that's land cover the next layer that we're going to need to do infiltration is a soils layer so i'm going to go back to our map layers i'm going to right click again i'm going to say create new raz layer this time i'm going to say soils layer that same type of editor comes up but now it's to pick a soils layer and this we're going to use what's called the g surgo soils database so i have that out here and i'm going to pick down here on the right i'm going to pick a g star.star so it can find my my information and i'm going to go to this directory what i'm going to look for is this is the geosergo data base but i'm going to look for the the gdb file so this is all the data but i want to just grab this one geodatabase file and i'm going to say open now it's reading that file now that file is quite large because it's for the whole state of pennsylvania there's a lot of information in there so this is going to take a minute to read all this information okay so we'll have to bear with me a minute but what's happening is it's going through and finding soil classifications in soil texture class and hydrologic soil groups okay which are contained in this file and once it reads it in we can choose to either use soil texture classes or hydrologic soil groups the scsa b c d or a combination of both for this example since we're just going to use the ses curve number infiltration method i'm just going to use hydrologic soil group for the standard soil classification that i want to glean out of this file so that is the over here so here's the the name field and so here we've got hydrologic soil group texture group or merged it's texture and hydrologic soil group or just map units so we're going to use hydrologic soil group okay and so you can see that that's using the scs methodologies of a b even a combined bd cd etc again we're going to give this a name so in this case i'm going to put this data in the soils data where i want to have it and i'm going to call it test soils data and i'm going to go ahead and create that okay so now it's creating that so it's reading that database for the same rectangle that we have previously defined and it's gathering all of the hydrologic soil groups polygons and then their classifications and there we go and so now i can plot that and i can see that i have different um soil groups in some places there's there's none okay like over the channel it doesn't have anything in this case which is okay and so we have that layer now okay okay so now the next step is to create an infiltration layer and so again we're going to go back to map layers we're going to right click create new raz layer and now we're going to say infiltration layer and i have two options here infiltration layer from land cover and soils or infiltration layer from a shapefile in other words if i have a shapefile where i already have polygons and infiltration parameters defined i can just go and import that maybe you created that with htc hms and you exported it out and you could use that straight away here we're going to use land cover and soils so it's going to bring up this editor where you pick an infiltration method i'm going to pick scs curve number you pick a land cover layer now you can use just land cover or just soils or land cover and soils so i'm going to pick land cover test and for soils i'm going to pick soils test and there's a field here that says time between rainfall events to re-establish initial loss in soil moisture so this is an option this is something that's not standard for s but we have it in ras when it basically says that if i put in for example 24 hours if this thing goes 24 hours with no rainfall at all it's going to reestablish the initial loss and the infiltration parameters back to the beginning and so that this is helpful if you have an event that's a multi-peaking event okay maybe you have a small event at first a drive period then a big event but you need to model the whole thing because they're both producing combined runoff and again let's give it a name so here i'm gonna go and i have a um i'm going to just leave that i guess in soils and i'm going to give it a name of test infiltration and hit save and then create okay that gets created rather quickly and if we plot that what we're going to see is now we have a combination of over any group grid cell of the land cover type the um hydrologic soil group okay um and et cetera et cetera oh whoops that's not the test infiltration one here's the test infiltration one so we have the land cover type in the soil group so the next step now is to define the infiltration parameter so if we right click on this test infiltration and we say edit infiltration data up comes a table and in here in this table is every combination of land cover and soil group so there's this no data for land cover and then soil groups then there's mixed forests and soil groups so there's a lot of parameters here because now we're trying to define infiltration parameters based on a combination of a land cover and soil group and so we've got if we look 152 of those combinations now again i've already done this so instead of trying to enter a curve number i wouldn't normally have to enter a curve number by hand an initial abstraction ratio and then a minimum infiltration rate minimum infiltration rate is also uh not a standard curve number method but it's an htc ras option so let me go back to the one i've already created and i'm going to say edit that data and i'm going to go ahead and grab those values from this table since i already did this by hand previously to speed up this demo and then i'm going to go back to the one i just created test infiltration and say edit and i'm going to paste that information in okay come on okay there it's ah there's a different note there it is okay all right so i got the information paste in though okay and we're gonna say okay all right so now when i go over top of this i'll see that i have not only a land cover and a hydrologic soil group but i have a curve number an initial abstraction ratio and a minimum infiltration rate okay so now i have all the layers i need to find so once i've defined these layers the next step is to go up to the geometry data in this case i have a single geometry and i'm going to right click on dramas and manage geometry associations here's where you tell it for every geometry you have what layer you want to use for manning zen so here i have a land cover dataset or the test one i created okay and then what do you want to use for infiltration so there's none maybe i'm not going to model infiltration or here i got the original infiltration one and a test one i created i'm going to leave it as the original and then percent impervious so as i mentioned i like to define percent impervious separate from the curve number because then i get immediate runoff for any rainfall that falls on cells that have percent impervious and i think that's more accurate so in this case the land covered layer is the same layer as defining the mannings and values and the percent impervious but the infiltration is just this infiltration layer okay so that's what you need to do uh to do once so you've created a to summarize you create a land cover data set and you enter n values and optionally percent impervious you can create a soils layer optionally you don't need it because you can just do infiltration based on land cover only if you want but i think it's important to do soils and then you create an infiltration layer that's a combination of the of soils and land cover or option it can be land cover only or soils only i chose to use land cover and soils when i created my infiltration layer and then you define the parameters that you need for that layer in this case because we chose curve number we needed the ses curve number the initial abstraction ratio and then there's an option in raz to put a minimum infiltration rate and what that minimum infiltration rate does is normally in the ss curve number if there's enough rainfall and the ground gets saturated it the infiltration goes to zero in the scs curve number method but with rash you can set a minimum infiltration rate such as maybe the saturated hydraulic hydraulic conductivity okay so that's everything we needed to do for razmapper and defining infiltration so our infiltration for this geometry however we use it is set so i'm going to close that the next thing you want to do is talk about spatial precipitation for that we're going to go to the unsteady flow data editor and in this editor there's a new tab called meter logic data and i'm going to press that tab now i already have this set but i'm going to walk through you how i set it up the way we set up spatial precipitation is we have this precipitation evapotranspiration and we have to normally that would be disabled when you come in you have to say enabled and when you say enable then you get some other information that pops up in the window this next section called meter-like stations is if you're going to use point gauges and that's how to define the point gauges but we're not going to do that in this example so we're going to go down to meteorologic variables precipitation and the first thing is that you have set is the mode so you can either have point data gridded data or just a constant rainfall we're going to use gridded so there it is gridded after that there's the source of the data so for grid of data there's two sources either hec dss or raster files so if you use dss that means you used another program to get gridded rainfall into dss now we have a piece of software called met view that can help you do that if you use choose the raster files that means maybe you're importing directly the national weather service raster files which are can either be in the form of what's called grid files or netcdf now since i've chosen dss i have to pick a dss file and and a dss path name so i'm going to go ahead and do that so here i have a precipitation file that i had created and we used met view to actually create that i'm going to open that it's going to read that file and show me all the path names available in that file okay i'm going to turn this off so there's lots of rainfall data here and the good news is i don't have to pick a path that's exactly in my time window i just have to pick a path that is the right data and we go to run it'll automatically change the d and e parts to grab the right data so i can pick any one of these paths okay and so i just select it and i say okay and i come back and there it is the dss file and path and i just say apply data file save on study flow data and i'm ready okay so that's it okay and now at this point we would run the model this model takes about eight minutes to run so i'm not going to run it okay but you would just go and compute and i'll give you show you what happened for runtime messages when it did run so one of the things that happens is that it goes through and it writes out the geometry et cetera and it runs the geometric preprocessor and then there's this thing that says writing event conditions and it says okay there was no wind data but hey wow i did find precipitation data so it processed the precipitation data and told you how long it took to do that okay so that's how we know that that it used the precipitation data because it showed that it processed it during the geometric pre-processing phase okay and then it went ahead and ran the model you can see it took about eight nine minutes and then it finished so now let's go and look at output okay we're going to open raz mapper and the first thing i want to show you is displaying the precipitation so we can go to our results layer and this plan was called gridded precipitation infiltration and there's an event conditions layer and in that are layers like wind precipitation layer and precipitation accumulated so let's turn on the precipitation layer which is incremental precipitation i'm going to zoom out to make this make more sense okay and i'm going to start at the beginning here and then we're just let's just animate this so what it's showing you is how the storm moved and these are hourly precipitation values and on the lower right you can see the the the legend if it gets up to purple those are like one inch per hour it's really intense okay so i'm going to go ahead and stop that so another thing we can do is we can plot the cumulative precipitation in the same way okay and so now i'm going to plot the cumulative precipitation so here i am seeing rainfall accumulating at each cell and so i can see that for this particular storm it was more intense actually away from the basin over here but the basin did get caught okay and we're approaching about six inches of rainfall that fell over the watershed during this time window this case it's about four days okay so that's the cumulative preset now another thing i can do i'm going to turn incremental back on and i'm going to zoom back in another thing i can do is ask for some time series plots so i can this place just do incremental i can click anywhere in the watershed right click and say plot precipitation and what i get is this nice hourly hydrograph so we can see that we had quite a bit of rain falling the first couple of days and then it went dry but i had to run enough simulation to get all this runoff off so this most the storm actually fell within a couple days at the beginning on the 9th and 10th and a little bit on the 11th in this case for this window now i can do the same thing with cumulative precipitation and i can say plot accumulated precipitation so here i get a nice accumulation of rainfall and again from the cumulative i can see where the most intense portions were like in here and so forth and again most of the rain fell over these first couple of days all right so that's how to look at the rainfall now let's talk about the the runoff so here let's just look at depth and at the beginning of this event i on purpose started this whole model completely dry now there is an upstream inflow that's going to come in to fill this reservoir and then there's but that's the only inflow of this whole model so let's go ahead and start animating okay and we can start to see water showing up now one thing i'm going to do is stop in order to see rain falling on the grids what you're only going to see is rainfall excess so if rain falls on a cell but it's 100 infiltrated there's no water so you're only seeing rainfall excess on the land surface because that's what's running off so i'm going to zoom in enough so we can see more of what's happening there and i'm going to go ahead and animate some more okay there's a second wave to this storm coming up and there it is okay let's zoom out a little bit so if i grab a hold of this you can see it better so i'll go back to zero and then i'm going to move okay so like over in here you can see these rainfall falling on some of these cells now the other thing to remember the rainfall that falls on a cell is computed as a volume of rainfall excess and it gets put into cell but it goes to the lowest point in the cell so if i turn on the geometry we have these larger squares so it doesn't fill the whole square because remember this is really steep so when rainfall falls in the cell it's put into the lowest point of the cell okay but it's accounting for the full area of the cell and the rainfall that fell over the full area computes the infiltration and gets the excess converts that into a volume of water and adds it as a volume of water inflow into the cell okay and then it starts moving it based on the two-dimensional flow equations okay so if we zoom out i'm going to turn that geometry back off we can just quickly go through from from dry and i'm just going to slide this so you can see the water coming up and down and then here comes some flow from the reservoir because i had a big inflow from the reservoir from upstream also now what if you want to take a good close look at the infiltration parameters on kind of a grid cell basis there's some other layers you can create so if i go to the plan name and i right click i can say create new raz map layers okay and from here i can create additional layers okay and there there's hydraulic layers and there's additionally there is what's called additional 2d variables and under the additional 2d variables right now we have cumulative excess cumulative infiltration and cumulative precip depth so i'm going to collect connect select excuse me cumulative excess and i don't need to pick a profile you can just grab the first one and i'm just going to say raster and it's going to allow me to dynamically look at this in time so i'm just going to say generate for current view and i'm going to say add map and it added it i'm going to grab cumulative infiltration and i'm going to do the same thing and added that one and i'm even going to do cumulative precip even though i have a precipitation layer under event conditions i'm going to do that anyway because this is based on the cell level plotting okay all right so now i have these layers and let's just look at one of them like cumulative excess so on this legend over here dark blue is actually zero i'm going to tone this down a little bit so we can see through it so i'm going to go to layer properties and i'm going to make that so we can see through it but now if i go ahead and i start moving forward in time i can see where i had excess so notice i had a lot of excess over the stream which makes sense because remember i define the channel as a hundred percent impervious so any rainfall that fell should be hitting the stream in other areas away from the stream in the stream i have about 2.8 inches but other is because of the land cover and soils and infiltration parameters i have quite a bit less 0.28.6 whatever okay i can also click and say plot time series of cumulative excess depth okay and that should come up and there it is so now we can see for where i selected the cumulative rainfall excess in time and this particular cell there was about 3.6 inches of rainfall excess remember this event had about six inches of rainfall so that means over two inches went into infiltration and over three and a half went into runoff and if i want to look at the infiltration i can do the same thing again i'm going to tone down the intensity and now i can see how water infiltrated so now i'm seeing that okay in the stream there was zero infiltration but away from that lots of infiltration based on color okay and so again i can plot time series for any cell etc etc okay all right so that's basically what i wanted to show you for this video i hope this helps take care

Channel: HEC RAS

Views: 14,678

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Id: tje7q0djHWc

Length: 28min 18sec (1698 seconds)

Published: Wed Jan 26 2022