willms: i ansome peole mighwalk pas here an think, "oh, yh. it's just orgrown grass.no. it's low-lyi ea thatas certain vegetion in ithat is e perft vetation wn you want war to absb and be able to ssipate a more gradl rate. mean, itoesn't loolike a t of natur science,ut ther's a lot o tural sence thagoes int it. wagoner: cts less ave green frastrucre becau this is low-maintenance. this is a model of a part of the city as the mn draige basin yohave an dergrounsystem, e whitnes undethe ear. the id was to t the waternto thespipes, tget thatater tthespumps and ush it o. that w the method. wiiams: trh of theatter is, ere is nway to sve our wat issues th just r pps and tbines.t's t enoughit will never be enugh. waggone you kno decades of dong thwrong thg usuall ki you.e got oudeath warning 2005. williamsif the was a liticawill to ke sure hat thisity seesnother00 yers, it wld meahaving ery beatiful, very aesthetic blueways along with greenways throughout the city, us living with water, so that when that next storm comes, because it's going to come--that's a fact-- that water has

>> reporter: this man, taj gibson, says there's nothing willms can say or do to convince him until theas been out longer. what would it be for you, if you had to put a number on it? would it be after a year, after two years? >> 3-5 years. >> reporter: and so, what do you make of the millns and millions of people that have gotten the vaccine, and have been okay? >> everybody is different. everybody's individual body is differen >> reporter: it's been quite a journey for williams. he's had a change of heart-- not only about the vaccine's safety, but also what he now sees as his responsibility to convince others. he's working on them one at a time. for the pbs newshour and kaiser health news, i'm sarah varney in hartford, connecticut. >> woodruff: in ethiopia, a civil war that's been raging for more than a year seems to be entering a new phase. rebel forces from the tigray region are relinquishing areas seized from federal control, but the government of president, abiy ahmed, says it is skeptical of the rebels' ultimate goals. as ali rogin reports, the conflict may be evolving, but peace