Above the dam is the flood basin which captures the flows of the mountain watershed of the Arroyo Seco . This area is now called " Hahamongna " , a phrase meaning " Flowing Waters , Fruitful Valley " , a remarkably different designation than the name given the area by the Spanish explorers . Hahamongna also refers to the original Native American tribe of the Tongva Indians who once inhabited the area . By 2011 , the flood basin had filled with debris brought down after the 2009 Station Fire , reducing its effectiveness as a flood control measure . The County of Los Angeles conducted public hearings on the Environmental impact statement before selecting a method to remove debris from the Hahamongna area . In 2014 , the Board of Supervisors approved a five-year project to remove 2.4 million cubic yards of sediment ( ) from the basin despite strong opposition from neighbors and recreational enthusiasts . The opponents contend that hundreds of trucks would be required that would increase pollution and noise . They also say that the wildlife habitat will be destroyed and interfere with hikers , cyclists and horseback riders who use the area for recreation . The alternative supported by Pasadena officials would have removed 1.4 million cubic yards of sediment ( ) and provided regular maintenance . County officials supported removing more sediment to reduce the flood risk for most major storms
Station Fire
2009 California wildfires
Arroyo Seco (Los Angeles County)