I am doing Project on Drainage basin, to find out the Elongation ratio I need to find out Basin length, Can any one of you tell me how to find out BASIN LENGTH using ArcGIS or any other way. My data base is like below Image

enter image description here

(i just uploaded this image from internet)


If by Basin Length, you mean the maximum distance from the watershed boundary to the pour point, you need to use the Hydrology tools from the Spatial Analyst Toolbox.

  1. First fill the sinks of your DEM using the Fill Tool.

  2. Then calculate the Flow Direction, using the Flow Direction Tool

  3. Finally Use the Flow Length Tool.

    The value of the output at the pour point, is the maximum Flow Length.

  • Does Flow Length and Basin Length Same? – Mahesh Dec 19 '12 at 10:15
  • I have heard of Basin Length being defined as the maximum length a water drop travels, from the ridge line (i.e. watershed boundary) to the pour point. Even Your Images seems to indicate so. However, I'm not an Hydrologist, so my understanding of the terms might not be the correct one. – Devdatta Tengshe Dec 19 '12 at 11:20

Are you talking about a line or a polygon?

You could go to the attribute table and then right-click on top of a column and select 'calculate geometry' (or something similar unfortunately I can't access ArcMap at the moment to check this).

In the pop-up you can select length, I believe.

Hope this helps.


you can calculate basin length (Lb),using a simple tool that is lenght measurement tool, and remember that you have to calculate from the mouth of the river (that is end point) and source point through the center of the highest order of stream to perpendicular. this method is Schumm 1956 (Basin Length Lb. karamat Ali,Dept.Env.Sc, KIU, Gilgit, Pakistan

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