ArcGIS T17: How To Calculate Curve Number From Soil Map

hi there welcome back so today i'm gonna show you how to calculate curb number from soil maps so we already have idea about this type of soil map right we downloaded this data from soil sergo website and we process this soil map and now i'm going to show you how to calculate curb number because if you know the hydrologic soil group it is in a b c d and then you need to calculate the number because the curve number ranges from right 30 40 to 100 or 99 so it depends on the curve number if you want to see the soil property and if you want to use that in your loss function if you want to double off any heck sms model you need to know the curve number for your specific watershed or sub order set so how can you calculate that one and if you need that so what are you going to do you have to be able to calculate the curve number right so now i'm going to show you how to calculate that curve number from this soil map because i'm going to show you see if i open that table you can see we have different soil properties we are not going to focus on all of them what we are going to do here see hydrologic file group we already have that right for each of this polygon we have this different soil group but we don't have the curve number here in this table so i have to prepare that one i'll show you because we have this data already tabulated in u.s army crafts of engineers website and you can even find it from different hydrologic information book right you can do that it's published already there and i'll calculate the corresponding curve number instead of d right so we know the hydrologic soil group for this specific area location but what will be the curve number is it 80 or 90 or what is the value and we need that specific value in our equation if you want to use the loss method as curve number method then you have to provide that curve number and then you need to calculate curve number right you have to do that so before going to calculate that one i'm gonna just export and i'm gonna create a new project so that you can follow right what i'm gonna do each time i open a new project a new tutorial i create one a separate project for it right so here within this folder i'm going to create a new folder called cn or curve number calculation okay and inside that curve number calculation what i'm gonna do here i'll just uh save my okay just gonna open it and then i'm gonna add and file person it will be chef file and then i'm going to save that as soils okay i'm going to save this as soil curb number so it will be the current number will be chef i'll put it that way so i have that i don't need that one what i'm going to do i'm going to open a new project and each time i do i'm going to create inside that curve number calculation i'm going to create one new file geodatabase and that zero database will be curve number okay cn calculation then i'm gonna add this so everything will be stored there see and it is going to open a new one and if it is this one if i open the soil map now i have access to this one so it's pretty simple right and see if i just want to save my project before saving that what i do i just click this one store relative path name or path right and then i just save this as save as and it will be inside my curve number right i'm just gonna go back and here's the calculation of curve number and i'm gonna save that cn calculation and if i remove the part extra part and it will be mxd file so i have one folder inside that folder i have the jio database we have everything inside there and we have only one file as shapefile so if i wanna show you what we have inside the table we see we have different ids object artists we already have idea about this one right but the most important thing is that we have this hydrologic soil group see previously it was a long name but now it is short right so it is hydrologic soil group abcd it is same so we need to provide another column based on this column or based on these values a b c d right we have different values a b c d or c oblique d or b oblique d right whatever the value will calculate that one so we'll add one column at the end of this table and we'll add the corresponding curve number value right before that i'm gonna export this table as excel file we can do that we can click on our arc toolbox as we did before and then conversion tool and excel right we're going to convert from table to excel and let's see if we can convert it from table to excel and that's it i'm gonna select this soil and it's gonna take a while because it's a very big table right and then if i wanna save everything inside this one and let's see if it's gonna export it or not okay and then we'll open our table and we'll convert it to csb and we'll do some operation i'll search the corresponding values of crime number for this hydrologic soil group and then we'll do some operation there okay let me find the values we have curve number calculation and stress and inside that and we have that table okay let me just remove some columns from it so that we can follow right we don't need this extra table we're gonna yeah extra columns we don't need that we need only that hydrologic soil group up to this one i'm just deleting control minus and it's done even i'm gonna delete everything up to this one we don't need right any of them because it is already there i'm gonna just reduce the number of columns so what do we need we need curve number here cn okay so in order to do that we have to find the values from left side okay how can i do that if you go to google and you can search for card number table it will give you this one heck right heck is ms technical reference mineral and you can find this curve number values a b c d these are the soil groups and you can see that these are from scs tr technical reference and then 55 table number two to a and run of curve number for urban areas because our area is located in houston texas it is a city right it's uh mostly the urban areas and you also have another table for cultivated agricultural lands you can do that and we also have another one which is the other agricultural land these are the options we have and we have another one for a read and samuel right so i'm gonna use that first one so urban areas and we have see we have different options here the poor condition grass that is less than 50 percent and fair condition grass cover uh 50 to 75 percent okay since in usa the cd is also covered with grass and everything i'm gonna select this one okay this is the moderator fair condition even you can use the other one it doesn't matter i'm just gonna show you how to calculate curve number from this table right if you know your area and the description of your area and the coverage or the vegetations or other informations then you can't even use that rows it doesn't matter okay i'm going to copy that and i copied it and i'm gonna paste it there and let me okay let me create a column here okay we'll have in this way i'm gonna create a column or table curve number and i have a i have b c and d right so these are basically a b c d i'm gonna just trans form transpose this one so we have abcd but you can see that we also have b or d and we also have another group c r d right we also have that i'm to create the curve number for this one as well and we don't have any other like a b or right or other combination we don't have that if you check it you only have a b c d or it is either b d or c d so i have these two options right what i can do i can even cr right i can take the average between uh b right and d how can i do that i can just sum them up and divide by two that will be the average value so i don't need that right okay i can keep it that way it is all it is yeah it is also good if i wanna get the carb number these are my reference then we'll fill this column right the corresponding curve number from this table we need to do some uh operation here you need to know this thing in excel you can use your code even in python or in matlab or r to do the same job but i'm gonna show you everything in excel so that you can even follow you don't need to have expertise in programming language right so here it is it will be right c plus d and if i just make this that's pretty simple okay i'm taking average of this two and it's divided by 2 okay so we have these values we don't need this one we already have so what i'm going to do i'm going to use this table as reference and i have to fill this right this one so this will be 84 and b over b or d this will be 76.5 so i i have like so you can see how many rows i have so if you just copy and check one by one it will take right a lot of time you have like 24 000 rows so we have to use some automatic process and how can you do that this is the new thing you can know and if i want to use this condition right valley lookup valley lookup so it is going to look up this value d and then where it is going to look up from here okay so from there to there okay so we have to fix that you can use the dollar symbol then my lookup table it will be fixed to this one so i have fixed it and then if i give okay if it will look up everything in this table from this column the first value it will look up the d value from a to 81.5 and if it finds okay d it is messing with d then it will replace it will put here not d but 84 that's why i'm gonna give two and if it won't find anything then it will return false okay and i'm done okay bye bye so it will be false it will be false see it already got 84 right and if i want to repeat everything i have to double click on that and see it's done for b or d it is 76.5 and for a it should be 49 and for c it should be 79. let's find c we have c right c for 79. let's find a it will be 39 for a what is the value of that 49 okay so let's find a i can see one a 49 that means it is pretty and c over d 81.5 see 81.5 so that means it's accurately yeah just look for the value and replace this one so we are done with this one so what you have to do we have to join this table with the attribute table we have there so we have to save this i'm gonna copy this and i'm gonna create another csv file fresh csv file we don't need that we need only the values we have this and i'm going to save this as a csv file if it is okay then we can easily combine and join this table that we did previously right you can remember if you follow everything tutorial in the first lab i did on arcgis when i downloaded that nhdplus daily flow line and then i added that in all stream flow to that one based on the com id so that was that one so it will be curve number calculation and here i'm going to say that as command delimited and it will be curve number okay so i'm going to save that and it's there i don't need this one anymore i'm gonna go to my arc map and here it is and what i have to do i have to add that table first right so here it is i'm gonna add it so what i have inside that one if i open it you can see that we have that right we only have these values so hydrologic soil group and the corresponding curb number but in that table we have the hydrologic soil group but we don't have the curve number so i'm going to copy this curve number from cn to soil because we have other information there and it's a map right so at first i have to join this two table i'm joining this curb number table right i'm going to select that hydrologic soil group where it is let's find that hydrologic soil group which one is that probably yeah let's find that name of the column because it's a very big okay it's a very big hydrologic that takes time to find that it should be not there it should be here okay that one okay that one is the short name hydrologic soil group okay dcd and then we have the curve number table we're going to join this table with the previous one and we have the same field there we're going to keep all record i'm going to click ok so the tables are joined right so we i should do another thing before joining this one okay i have to repeat the process see we have joined this table but we before joining that one what i have to do i have to remove this joint first and let me just show you that one i'm removing this joints but before going to joining this table i have to add another field of curve number because i have to copy the curve number right from that table to here so we have to follow a specific guideline i'm going to add a new field as curve okay curve number i'm giving the short name as curve name and it will be double since we have a decimal degree there so we have this will fill this will copy curve number from that table to here right that's why i'm gonna join this one here we have to join we are gonna select we have to find this value again don't worry i can find it pretty quickly because i know it's there right it should be right there okay we got it and we have done this before i'm gonna keep all this record i'm gonna click okay it's joined let's open the table and do the job we need so here it is see at the end of the table we can see we need which field we need this field right because this part is from that curve number table we need to fill up this field so if i select and if i just right click and fill calculator then what you have to do see it's already selected soil from soil shift file and it selected that column name dot curve number and i'm gonna copy everything from right this one from curve number see from carb number table so that's why the cn is the name of the table and it's a csv and then we have the curve number so if i click okay then it will copy everything from this column to that column see we already have that can you check that the same value so we have we don't need this part so i'm gonna remove i'm gonna just right remove the joins we have see that's the benefit remove all joins you can see we don't have the last part of the table other than that curve number see we only have the curve number so our original file is preserved we don't need this one we utilize that one and we're gonna just throw it okay so we're done if i wanna show you how to even change the color because it is not looking nice i'm gonna change it and based on that curve number i'm gonna do that okay i'm gonna click quantities and then graduated color and i'm gonna select that curve number right now and then if you want to even yeah what you need don't need graduate color we need basically uh different okay unique values if it is unique values and based on that curve number it will give you an idea about okay i'm adding all the values we have see these are the values we have and if i want to select this one it will give you a nice math and now we can see that here right you can see our curve number these are the curve number and this part and you can easily identify right these values 84 we have 84 all these locations and we have this one right 79 and that is 76 right so we can even use this one because we have one watershed there we have another watershed there we can use these values and in between these two we have mix so it is 69 here right it's 69 and we have also 49 this place are not that prominent we have very small area so if you want to add your base map we can do that as before and you can complete your map as usual that's what i already demonstrated so that's that right so we are pretty good and this map i'm gonna even make it a little bit better than what we have right now so i'm gonna add the north arrow first it should be right there if i want to expand it a little bit what i need next step i need to even add the scale bar as i2 always right that is in meter but we don't wanna do it as meter we need to change it as miles right as miles and that will be that and if you want to change the format you can do that right you can increase the size as 12 make it bold it will look nice that's okay and then if you want to add the legend that's what we need which one is which then it will give you we don't need the title as lessened we're gonna identify which one is that so we have pretty nice math right there we have soil this is 49 curve number you can easily find out the location and area what else you need we need the title right we need the title so uh curve map okay curve number map curve number curve number math off sensor center right and just into a watershed okay we have pretty nice map and i'm gonna copy it because i'm gonna manipulate something there i'm gonna put it there and double click and i'm gonna replace it i'm gonna change the size and make it times new roman and bold and increase this title you can see it's pretty nice we have that map right there right we have the map and if you want to increase the size as before we can even do that you can even manipulate the boundary as before it did or you can put it this way as well and you can save your project you're done right this is what you can do these are the steps you need to do you can finish off here and what i'm gonna do i'm gonna export it and if you wanna make this right boundary just prominent then what we have you can even change the point right make it like 2.5 and it will be pretty nice right see you can see that it will yeah visualize so that's right pretty good what i'm gonna do i'm gonna save the map and export the math and it will be pretty nice and it's gonna ask where to save okay i'm gonna save as current number calculation that's it we have the pretty nice map it's exporting the resolution is also good and if i show you what we have here curb number calculation so that is the final output right we have for our study area see it's pretty nice right so that's that uh try by yourself and let me know if you have any problems so what i have done today we just calculated one model parameter that is also the input of hey ksms model if you select the loss method as curve number then we have to use this curve number for for your study area or for each of this star watershed because you need to change this you can't even use one valley for each of them because if your area is bigger so it only represent one curve number right then your calculation will be wrong and yeah that's it so you can try by yourself and you can use this type of math in your report in your paper wherever you need you can even do that and you already saved your project as a single this file so you can even make a zip file and you can send it to your client or your teacher or any other person then he'll be able to open the project as it is right so that's that so we are done with uh the calculation of curve number and if you have any query question let me know and practice and just uh yeah thanks for watching this video and i'll just change the title in the next video and i'll do different things so until then stay safe and take care bye

Channel: Md Arifur Rahmahn

Views: 1,351

Keywords: curve number, arcgis, arcmap, how to calculate cn grid

Id: 1hbKEvhgEYY

Length: 24min 17sec (1457 seconds)

Published: Sat Sep 11 2021