The Blackwater, after bending south at Cappoquin, enters a deep ravine, the sides of which rise to between 300 and 400 ft. Now if a dam 80 ft. high were formed across the river at Dromana, it would, after forming a lake about Cappoquin, make its way to the sea at Dungarvan. Similarly if the east and west passages of the Lee were blocked the river would go along by Midleton to Ballycottin Bay. The Bandon too, under similar circumstances, would find an outlet by the Owenboy valley and enter the sea at Cork Harbour by Carrigaline.
