Severe weather increases demand for river dredging

With the high water, barge lines have had to take extraordinary steps to avoid damage to their fleets, protect cargoes, and meet delivery schedules. Ryan Guidry photo

Posted on December 8, 2020

Unusual weather patterns that produced sustained high water along inland rivers and severe hurricanes in the Gulf have put extra stress on locks and dams and flood control infrastructure and caused extreme shoaling in many areas of the Mississippi River system.

The situation has required the U.S. Army Corps of Engineers and its private contractors to deploy more equipment to dredge parts of the river to restore safe navigation, and an emergency act of Congress to pay for it.

“In the last year or so, if you look at the National Weather Service data, in the 26-year period of record, 2019 and 2020 were the wettest periods on record,” Edward Belk, programs director for the Mississippi Valley Division of the Corps in Vicksburg, Miss., told the annual Waterways Council Symposium on Nov. 12. The event was held virtually due to the pandemic.

“There was sustained high water from last fall until June in vast parts of the waterways system. Continuous high water stayed on our locks and dams and flood control infrastructure for a record period,” he explained, creating “tremendous shoaling across our system, and as a result we’ve had significant dredging demands that we’re working very hard to service this year.”

The Gulf of Mexico was hit by five strong hurricanes this year, and unusually heavy rainfall last year caused historically long periods of high water along many parts of the inland system. This produced a significant amount of shoaling, which occurs when rivers get filled with silt and sediments that impede navigation. This is a natural occurrence, but is often worsened by severe weather events.

To remove shoaling and restore river depth that allows safe navigation, Belk said the Corps dredged 277 million cubic yards nationally in 2019, a significant amount. About 119 million cubic yards, or 43 percent of the total, was done in the Mississippi Valley region.

“We look at the trends of climate variability and last year we had historically long high water periods and historic shoaling. And we’re seeing more intense storms and more of them,” Belk said in an interview after the symposium. “We are tracking the science and seeing things are behaving differently.”

The Corps is adapting by building its budgets two years ahead of time and reviewing how it anticipates and models weather patterns and their impacts. Communications and observations from vessels working the waterways are crucial to this planning, and science is guiding decisions, he said.

“Our job is to be transparent and make sure we’re ahead of the curb and anticipating where the shoaling will be.”

Congress has also been highly responsive, granting emergency funds for dredging and record budgets for waterways operations and maintenance over the past few years, as well as providing the Corps with flexibility to apply its resources to the most significant problem areas along the Mississippi and its tributaries, Belk said.

Funds were approved for a regional dredging demonstration program, and also to deepen the Mississippi River Ship Channel from 45 to 50 feet from Baton Rouge to the Gulf of Mexico.

This project began on Sept. 11 and is proceeding from downstream to upstream on the Mississippi River. Belk said deepening of the Southwest Pass and the lower nine crossings above the Pass will be done by next December, the two crossings above that by December, 2022 and the Baton Rouge, La., riverfront area (the upper limits of the ship channel) by the end of 2023.

He said an extra five feet of draft will make shipping more competitive by allowing vessels to carry more products more cost-effectively both domestically and for export, and eliminating the need to light load larger vessels so that they can navigate the channel. The Corps is working to minimize disruptions to vessel traffic during the dredging, he said.