Sacramento environmental groups are raising concerns about flood management construction on the American River slated to reach the Rio Americano High School area next year. The controversial ongoing work, part of the Sacramento Levee Upgrades project run by the U.S. Army Corps of Engineers, has come under scrutiny since beginning last year, as the erosion prevention measures have required the removal of trees and plants along the river. Up to 600 trees, including 100-year-old heritage oaks, will be bulldozed, according to the American River Trees group. However, the Army Corps has said the work is necessary to prevent potential catastrophic flooding. The work is designed to update the Army Corps’ standards from planning for a 50-year flood event to a 200-year event.