ArcGIS T9: How To Convert Vertical Unit of DEM and Generate Flood Inundation Map From Raster

hi there welcome back so today i'm going to show you how to convert the vertical unit of dem so previously what we did we just projected the dam right so the dam was in uh wgs coordinate system means geographical coordinate system so we converted it from geographical to state plane in feet but we didn't even convert the vertical unit because the dem data that uh contains a vertical unit right the elevation data set so it has two different unit one is the horizontal uh unit and another one is the vertical unit the horizontal unit was in degree minute so we converted that one from degree minute to straight plane feet okay but the vertical unit is still in the meter so now we are going to convert that vertical unit from meter to feet and then we will convert that if we have 10 meter or 10 feet height of storm then what will happen what will be the flood inundation area or what will be the flood inundation map and if the storm height is 20 feet then what will be the flood inundation map and how much land okay or how many square kilometer area within the study area will be flooded or affected by the 20 feet or 10 feet height of storm so let me quickly show you that one so here it is if i share my screen pretty quickly then i'm going to show you see that is the last one okay we left here and then we're gonna start from here right this dem is in uh meter you can see that on the left side minus 7 to 63 so here we have the elevation 63 meter and the elevation on the right side we have the lake and it is minus seven feet seven meter okay seven meter so what i'm gonna do i'm gonna convert that vertical unit so what we converted we converted this horizontal unit it was previously it was in uh decimal degree but now it is in fit okay state plane so how can i do that we have the option here see we have to click on arc tool every time everything is there and then we have to click on special analysis tool if the tool is not activated for you and if you can't find that click there customize and then extension and then just okay if that is uh turn off so turn this on and then you will find it there okay since i have already done that so here it is if we click there or expand spatial analysis tool then you have to go to map algebra if you want to do any raster calculation you have to find that raster calculator so we have that raster calculator there within map algebra we are double clicking here if i double click then what we have i have the dem okay that dem sends us into ws so that is the projected name we converted it from wgs to state plane i'm double clicking on that one so the vertical unit is in meter so how can we convert it from meter to feet it is the conversion factor 3.28 right so we know 3.28 feet is equal to 1 meter then i have to use that star means that steric is basically the multiplication sign here in this window and then three point two eight then it will be converted to feet okay then i'm gonna even save it where there okay so dem d e m so it will be like uh fit i'm giving the unit dm fit okay damn fit and then if i click okay it will convert so it is processing so you can see that raster calculator it is even calculating cell by cell because we have basically that is a 100 meter 97 meter by 97 meter if i check that if i click here see open if i open that definitely we'll see that see x and y the cell size 97.44 that is the feet one cell size is this one okay and we can now easily calculate the cell area 97.44 divided multiplied by 97.44 okay and then what we have here see you can see the change the unit vertical unit it got changed right previously it was -7 and now it is minus 22.97 if you multiply 7 you'll get that value and the highest one was a 63 and now we have 206.64 right and now we can even convert we don't need this dim we'll work on our feet okay since we already converted everything in feet and in usa they use basically feet they don't use that metric unit and this one if i use this one right or okay no since it is elevation i can even select a different one the same one i can select okay i can select this one as well no problem it it will be just opposite of what we have just invert and then we'll have the lowest value there but it is it is in feet okay even if you wanna convert it to different color panel we can do that we can go for this one okay so i think this okay it looks good but we can keep it normal okay now it looks good right the blue deeper blue is the minimum elevation and that is kind of red so it is highest elevation we have so now what we have to do if i wanna even calculate that okay what will be the flood affected area if we have 10 feet height of a storm right and what will be the area we have to be able to convert that so how can we convert that right that is the raster operation i mentioned that one right previously so when we'll download this dam and we'll convert it to this coordinate system to that one we have already done that and now we converted the vertical unit right from media to feet now we are gonna do some rest or operation so the query is what will be the flood inundation area or how much land or how many kilometer or mile area will be affected by a 10 feet storm right so we have to use that raster calculator again clicking on that arcmap and from that one special analysis tool and then map algebra and then from map algebra to rest or calculator so just you have to keep in mind that okay if we have 10 feet height of storm then it will inundate right it will it will uh just try to flour everything but not more than 10 feet because we know the height of the storm is 10 feet the surge is coming it is 10 feet so the query should be feet from the feet a.m this one and it should be less than or equal to 10 okay this sign if i use this sign so give me another set of damn or dem what is basically less than or 10 feet since i'm selecting the feet the vertical elevation so that will be the 10 feet because everything is in feet now i'm gonna even save it there so this time it will be dem and it will be 10 feet okay okay 10 feet 10 feet means the value maximum value is 10 and minimum value is that right minus 22.97 so it will give us the maximum elevation up to 10. so that area will be affected okay now i'm gonna save it okay let me save it first it is working it's calculating checking every cell and if the elevation is 10 or less than 10 it will extract okay so i think we have that so we have only zero and one we'll check that later no problem and now i'm gonna even calculate if the storm height changes if it is 20 feet then what will be the area let me do the same thing again but this time it will be 20 feet d dm and feet are less than or equal to 20 okay then we're gonna save it as dem 20 feet dem under score 20 feet so this dm will show bigger area right because if we have 10 feet storm definitely it will flood more area still it is calculating and then it's checking and definitely it is going to add that 20 feet now what do we have to do we have to do some processing we don't want to see that one okay we want to see only that flooded area now we have to calculate that area right we'll do that how to do that so now what i'm gonna do we have zero and one zero means here zero means we don't have any these values are higher than ten feet and one means these values are less than that is kind of query rate binary uh yeah we asked basically the binary query and then i'm going to remove the zero value how can you do that just right click and go to properties and then symbology and then you will see those valleys see we have more areas like zero value that are not flooded because these elevations are more than 10 feet i'm selecting this one once i selected this one i can remove that part okay i'm gonna remove that it removed and then i'm selecting there and i'm gonna select that as water right deeper water okay that one blue and applying i have that water so how can i calculate the area right the flood inundation how can we do that because we know by this time what is the cell size it is 97.44 and 97.44 right definitely we can calculate the total area right and what happened for 20 feet same thing we can do open it go to property symbology click on zero value and remove that and we have this one double click and change the color to uh this okay just a mild blue okay mild blue sky blue and then we have deep blue we have sky blue so sky blue should be there a deep blue should be here okay i have to click that one then i can shift it okay so now we can see the deeper part deeper part is basically that deep blue right that is the 10. if i use 20 feet a storm so it will go up and it will just flood right it will flood more areas how can we calculate the total area for 10 feet let me just right click on that i can even open the attribute table this time and i'll see the number right i can see the number one or zero so we can see the number here and we can calculate how can i do that see okay i'm just calculating add field if i add field flood okay flood inundation if you have flood inundation area maybe it's too long let me check it if i give the double flood inundation area okay we have flood inundation area so this number of cell that contains no water so this will be dry but this cell this will be wet and this cell will be flooded so what will be the area right we can do this operation here can you do that okay if i click here field calculator see this time this calculate geometry is not activate activated right so field calculator what we can do here see we can select the count discount number of count and if you multiply this by what by that number okay 97.44 into 97.45 so what it will you'll get you'll get the area in terms of square feet but that value will be pretty big right so we don't want that we want to calculate the area in terms of square mile since it is in feet so we have to divide these okay we have to divide this value by what so what is the value per square mile so we know the five two eight zero feet is equal to one mile right so we have to divide these by this five two eight zero multiplied by 5280 then it will be square mile and if i click okay then it will calculate c so when the surge is 10 feet 76.88 almost 77 square mile area will be flooded similarly if we oh that is for 20 feet okay that is for 20 i selected 20 and if it is for 10 feet then what will happen we can do the same thing right we can add flood inundation okay flood inundation area and i'm going to select it as double and okay i have that right click field calculator okay then count and multiplied by 97.44 multiplied by 97.44 and then i'm gonna divide this by okay i'm gonna divide this by five to eight zero multiplied by five to eight zero then it will give us the square mile okay so when it's logical right it's 44 when there will be 10 meter storm the total affected area is 44 square kilometer when it is 20 so it's definitely this kind of double but not double because the elevation is not linear it is not linearly increasing okay so it's logical so this is how we can even compute right what will be the flood energization area so that's it see it's pretty convenient okay if i even change the color to our previous band like this way we did and that's it you can see that that is the flood inundation area and okay and okay that's it flood inundation area so i can even change the map as a flight inundation map okay flood inundation map of of our energy map for for 10 feet okay for 10 feet and 20 feet 10 feet and 20 feet storm storm stars okay so if you have any storm surge model and if you know how to if you just create a roster and then you can create that flood animation map this way so that is the raster operation by this time you already have the idea about that one okay so you can do that flat animation map for 10 and 20 feet is from source so that's it and if you want to add this okay if you want to export that map it's also possible let me just try to use different color and that will be which one i'm gonna select maybe this one let me try to select that one if i select it as opposite make it invert then what will happen okay it it looks good okay it is looking good okay so that is the flood innovation map for 10 and 20 feet of storm surge okay 10 feet and 20 feet 10 feet and 20 feet from search that's it so if i want to even export that map go to export as usual and then we already have so that will be t10 okay that will be uh t10 we i think we already have that but okay 10 1 okay and it is exporting the map as before and if you want to change this color you can do that it is possible okay so it's there see it's there that is the flooded generation map and i'll add this map as thumbnail you will see that okay so what we have learned from this tutorial how to convert the vertical unit of dem or any raster and after that what we did we even calculated the flooded generation map if the storm height is 10 feet and if the storm height is 20 feet and we see that it is not even double right and we converted how to calculate we converted even area extend right from square feet to square mile so everything is in us customary unit so that is the way and for calculating anything and if you have restore value i mentioned that right previously if you want to calculate the relative humidity if you want to calculate other thing and if you have precipitation data if you have temperature grid if you have other greed so what you can do you can use gis and you can do the raster calculator you can you can do that i'll show you how to make it automatic i'll show you everything so you can repeat this process so that you'll be able to do everything that i have just demonstrated and if you have any query you can post that in the comment box and stay safe until then thank you very much for watching see you in the next tutorial okay

Channel: Md Arifur Rahmahn

Views: 135

Keywords: flood inundation map, flood map from raster, flood inundation map from DEM, how to convert vertical unit of DEM

Id: l9E_eg1YpH8

Length: 19min 24sec (1164 seconds)

Published: Mon Sep 06 2021