To many Angelenos the word "river" conjures up not pastoral images but trickles of water encased in concrete abutting crowded neighborhoods full of warehouses and chain-link fences. To Amigos de los Rios founder Claire Robinson, the San Gabriel and Rio Hondo rivers are physical manifestations of the dynamic intersection of the past and the present. Through forward-thinking, environmentally sustainable projects that include the development of a large network of community parks dubbed the Emerald Necklace, Robinson is truly altering the course of the rivers, and the people who live near them. Each one of Amigos' completed projects teems with native plants and pays tribute to the rivers' rich Tongva and Latino heritage. Several times a month the Altadena-based group hosts community park-grooming and tree-planting events throughout the San Gabriel Valley. With each weed pulled or tree planted, you, too, can be a vital part of this effluent rebirth. (626) 791-1611, amigosdelosrios.org.

—Katie Datko