Elevation-Volume-Area Curve using Surface Volume Tool in ARCGIS

This blog explains how to make Elevation-Volume-Area Curve using Surface Volume Tool in ARCGIS. The curve is useful for making decision in Hydropower project and to design different components along with determining release policy, etc.

Refer Video tutorial here. The link to download the pdf is given at the bottom.

How to write address in python?

Python uses ‘\’ as escape character so it cannot be used in path. Either use ‘/’ or ‘\\’ but if you wish to use ‘\’ in path then put ‘r’ in front of path. Following example illustrates these-

Method 1:

'E:\\HYDROLOGY\\S2\\ArcPY\\OUTPUT'

Method 2:

'E:/HYDROLOGY/S2/ArcPY/OUTPUT'

Method 3:

r'E:\HYDROLOGY\S2\ArcPY\OUTPUT'

r REPRESENTS raw data.

What is ArcPy ?

ArcPy is a python site package. It is used in python to perform data analysis, data management, ect. Hence, ArcPy helps to perform the task of GIS in Python.

In Arc Gis version 10, python version used is 2.6, which is installed with ArcGis.

All you need to do is import ArcPy in python editor and start coding.

How to use Surface Volume tool to find Elevation-Area-Volume Curve?

Requirement:

·      Enable 3D Anlayst as-

Customize | Extension | Check on 3D Analyst

·      GeoPrecessing | Geoprocessing Option…|Check on ‘Overwrite the outputs of geoprocessing operations’

Ø This will append the output data of surface volume to the existing text file.

Ø If this option is not ticked/checked on then error occurs if you try to store multiple data to the same text file.

Steps:

1.  Import DEM of the catchment, in ArcGis, you want to find the curve for

2.  Open Python Console and write Code

3.  For single data (area-volume for one elevation only)

>>>from arcpy import *

* indicates è import everything from arcpy.

Now, Set output file location….

>>>Output = r'E:\AY\S\S2\ArcPY\SurfaceVolume\Volume.txt'

>>>arcpy.SurfaceVolume_3d('cat_dem.tif',Output,"BELOW",1600)

Parameters of Surface Volume Tool-

SN	Parameter	Explanation
1	In_rastersurface	DEM or TIN
2	Out_text_file	Output file location
3	Reference_plane	Specify “Above” or “Below” to calculate area/volume above or below the horizontal plane
4	Base_z = elevation to calculate	The horizontal plane above or below which area/volume is calculated

Note: While giving elevation input (base-z), it should be between maximum and minimum elevation value of DEM.

Fig. Figure showing Reference plane and base-z

(Image Source: Arcgis Website)

4. For Multiple data

Use for loop

Syntax: for i in range (start, stop, step):

                     {Write code here}

 Note: Here, replace the elevation data of step 3 with “i” to calculate for multiple elevations

Lets create for 200 m interval from 1800 to 3600

>>> for i in range(1800,3600,200):

...     arcpy.SurfaceVolume_3d('cat_dem.tif',Output,"BELOW",i)

(Here i represents the elevation. Area/Volume is found from elevation of 1800 up to 3400 with 200 interval i.e. 1800, 2000, 2200, 2400, …, 3400)

Why stop=3600 but data is calculated up to 3400 only ??

Note: In python stop value is excluded i.e. 3600 will not be calculated. If you want to calculate for 3600 then use stop value of greater than 3600 like any one of the value as - 3601, 3652, 3700, 3800, etc. (all are greater than 3600 so you can use any of them)

5.  Plot the data in excel or other software…

Final Code:

>>> from arcpy import *

>>>arcpy.SurfaceVolume_3d('cat_dem.tif',r'E:\AY\S\S2\ArcPY\SurfaceVolume\Volume.txt',"BELOW",1600)

<Result 'E:\\AY\\S\\S2\\ArcPY\\SurfaceVolume\\Volume.txt'>

>>> for i in range(1800,3600,200):

...     arcpy.SurfaceVolume_3d('cat_dem.tif',r'E:\AY\S\S2\ArcPY\SurfaceVolume\Volume.txt',"BELOW",i)

Output:

Dataset, Plane_Height, Reference, Z_Factor, Area_2D, Area_3D, Volume

..rcPY\SurfaceVolume\cat_dem.tif, 1800.00, BELOW, 1.000000, 2386036360.9595, 2737722134.2743, 1292870451541.2

..rcPY\SurfaceVolume\cat_dem.tif, 2000.00, BELOW, 1.000000, 2751422471.6363, 3163428393.3652, 1808497318967.5

..rcPY\SurfaceVolume\cat_dem.tif, 2200.00, BELOW, 1.000000, 3028033578.3525, 3487425353.1481,  2387809023310

..rcPY\SurfaceVolume\cat_dem.tif, 2400.00, BELOW, 1.000000, 3229310550.9426, 3724084680.6395, 3014856120712.8

..rcPY\SurfaceVolume\cat_dem.tif, 2600.00, BELOW, 1.000000, 3367325890.0696, 3886617696.2116, 3675457721085.6

..rcPY\SurfaceVolume\cat_dem.tif, 2800.00, BELOW, 1.000000, 3453274628.7979, 3987641478.238, 4358511131963.1

..rcPY\SurfaceVolume\cat_dem.tif, 3000.00, BELOW, 1.000000, 3504734282.3825, 4048058015.2732, 5054687151193.3

..rcPY\SurfaceVolume\cat_dem.tif, 3200.00, BELOW, 1.000000, 3541936569.2609, 4091009563.4753, 5759568714963.8

..rcPY\SurfaceVolume\cat_dem.tif, 3400.00, BELOW, 1.000000, 3563171917.2772, 4115247120.6426, 6470475092432.7

Area2D = Projected Area

Area3D = Surface Area

Elevation vs Area curve

Elevation vs Volume curve