SAN DIEGO (Border Report) -- Alter Terra, a binational environmental group, is sounding the alarm about the need to dredge the Tijuana River channel just inside U.S. territory to avoid massive flooding near and around the San Ysidro Port of Entry.
The group says the floor of the channel has risen by 10 feet over the years, meaning it will take less water for the river to crest over its levees.
"As the river turns it deposits a lot of sediment on this side," said Oscar Romo, director of Alter Terra in San Diego.
The group has received a lot of notoriety for setting up a trash boom across the river floor that catches hundreds of tons of trash as it comes in from Mexico preventing the debris from flowing farther into the U.S. and the Pacific Ocean.
Prior to working for Alter Terra, Romo spend many years with the United Nations and is considered an expert on water and its impacts on communities.
He believes it's time to remove layers upon layers of sediment embedded on the channel's floor.
The sediment is made up of sludge from raw sewage, dirt from construction sites, soil from Tijuana hillsides and other materials that come in from Mexico.
"Based on the amount of sediment that is here, the water has to flow above it. So, this geometry of the channel has changed dramatically. There has to be an adjustment whether to remove the sediment or to elevate the levees."
Romo said the U.S. Army Corps of Engineers is responsible for maintaining the river and could easily do the work as part of its maintenance plan for the area.
The other option is to raise the levees, which requires congressional approval and major funding.
"They would need to bring in heavy materials, rocks to elevate the levees, and it's expensive to do."
Romo worries if nothing gets done, a major storm event could send tons of water over the side of the levees and into the path of the PedWest pedestrian crossing at the San Ysidro Port of Entry, the Las Americans shopping mall directly north of the border and into Tijuana as well.
"We see more water coming every single year -- all of that water flows through here -- which is an indication we are at the risk of having a flood. We have enough evidence that sediment accumulation could be a risk."