How to use a specific AREA (km2) to create a buffer-like feature around a polygon (Area to Buffer)

Question

How to create a buffer (or buffer-like feature) based on a specific area (in km2)?

I have a specific area (e.g. 14.5 km2) and would like to lay this area as a buffer (or something similar to a buffer) around a pre-existing, irregularly-shaped polygon.

This buffer should be of equal width around the polygon, so that I can extract the distance between the outer margins of the polygon and the newly created buffer.

Is there a way to do this? I'm using ArcGIS Pro 2.4.0.

• Bera: The buffer area without/excluding the buffered polygon should be for example 14.5, or including the polygon? How exact does it have to be, for example 14.4-14.6 is ok?
• M_S: Excluding the polygon. The buffer alone should be of the specified area.
• M_S: Your suggested accuracy is more than fine.

Answer 1

I think you will need to use arcpy, or a complicated Modelbuilder model.

Example which you will have to adjust (can with bad while conditions run forever):

import arcpy
arcpy.env.overwriteOutput = True
fc = r"C:\GIS\data\testdata\ak_riks.shp"
bufferarea = 400000000 #Goal
radius_increment = 100 #For each iteration increase buffer distance with this
good_enough = bufferarea*0.1
arcpy.MakeFeatureLayer_management(in_features=fc, out_layer='lyr', where_clause="{0} = '1487'".format(arcpy.AddFieldDelimiters(datasource=fc, field='KOM_KOD'))) #Im selecting one polygon to test with
arcpy.CreateFeatureclass_management(out_path='memory', out_name='tempfc2', geometry_type='POLYGON', spatial_reference=arcpy.Describe(fc).spatialreference) #Create temp output fc
icur = arcpy.da.InsertCursor(r'memory\tempfc2','SHAPE@') #Insertcursor to insert new rows into it
dist = radius_increment
with arcpy.da.SearchCursor('lyr','SHAPE@') as cursor:
 area_diff = good_enough*10
 current_area = 0
 for row in cursor:
 while area_diff>good_enough and current_area < bufferarea+good_enough: #Buffer with increasing distance until these conditions are met. You should/have to adjust this line. To get optimal resultat without running forever
 buffer = row[0].buffer(dist) #Buffer
 buffer_diff = buffer.difference(row[0]) #Erase original polygon from buffer
 current_area = buffer_diff.area #Find area
 dist+=radius_increment #Increate buffer distance for next try
 print('Success!')
 icur.insertRow([buffer_diff])

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