christensen: people under 40 living here in the bay area today are very, very likely to see unprecedted annu flooding around the bay in their lifetimes. jacob: it's going to be fantastic in a city that is so vital and known for its innovation that we're going to be able to build this great venue here. christensen: a lot of these new buildings by the end of the century, including the golden state warriors' new arena, would have the ground floors at least potentially flooded or basement parking flooded. the warriors arena is, you know, contemplating maybe someday putting in flood gates so that their garages don't flood. they're thinking of raising pedestrian access so that it would be out of the water. san francisco itself, you know, built a seawall in the late 1800s to protect itself and this new land that had been created. you know, right now, san francisco is looking at spending $5 billion to repair and reinforce that seawall for another century. scholl: the areas that have been the least developed historically are the marginal lands around the bay, some of which are salt flats. others are