Actually it's not only because it's connecting two trade centres, rather it's the need to build such a wide dam so that it could stall such massive amounts of water, waves, and also earthquakes.

However, it's also true that the three most business oriented states - Gujrat, Maharashtra and Rajasthan - lie very close to it. If you've heard of Mumbai, that will be about 50 miles from the east of the dam.

Construction_and_Engineering

India Is Building a 60 KM Dam Across the Gulf of Khambhat

Coinsreporter

Actually it's not only because it's connecting two trade centres, rather it's the need to build such a wide dam so that it could stall such massive amounts of water, waves, and also earthquakes. 

However, it's also true that the three most business oriented states - Gujrat, Maharashtra and Rajasthan - lie very close to it. If you've heard of Mumbai, that will be about 50 miles from the east of the dam.