TUCSON, Ariz. - Flooding caused by a border security fence in southwestern Arizona shows the structure is being built too quickly and without regard for the environment,critics say.

Debris and water backed up at the fence during a storm July 12, leading to flooding at the port of entry at Lukeville and Sonoyta, Mexico, and at the Organ Pipe Cactus National Monument.

"One of the reasons for it was the debris that accumulated on the fence itself," said Lee Baiza, superintendent of the monument, a lush desert tract overseen by the National Park Service.

Environmental groups have criticized how the Army Corps of Engineers and federal contractors have designed and built a range of fencing and vehicle barriers along the Arizona-Mexico border.

In particular, they've denounced Homeland Defense Secretary Michael Chertoff's waiver of environmental laws to hasten construction of the 670 miles of fences and other barriers planned by year's end along the nearly 2,000-mile U.S.-Mexico border.

Much of the pedestrian fencing on the Arizona border consists of 10-foot-wide and 15-foot-tall steel-mesh panels, some featuring wide horizontal grates at the bottom to let water and sediment flow through.