You might want to research materials for your application.
Kelty tarps use polyester fabric, which is excellent because it doesn't stretch when wet but has a downside that it doesn't like abrasion.
You might want to look at MSR which uses nylon instead in their designs. Nylon stretches, especially when wet but it is much stronger and handles abrasion better. Might be better for areas where you have high winds. Their edges are curved using a wing design that stands high winds. I haven't used their new stuff but I have some of their older awnings that were designed by Bill Moss. They are legendary for light weight and durability.
I second Sailrite, great resource.
Oh, I don't mean to dis Kelty in any way, I have a couple of their tarps too. Good bang for the buck.