Learning to live with Humboldt Bay entrance shoaling woes
7/23/16
On June 29, Bar Pilot John Powell was able to lift the draft restrictions on ships entering and leaving Humboldt Bay, thanks to about 45 days of dredging by the Army Corps of Engineers that removed approximately 2.8 million cubic yards of sediment.
Maintaining the entrance requires use of one of the two large Army Corps dredging ships that are used for all West Coast ports, and the cost of services annually have been about $3.2 million over the last several years.
Congressman Jared Huffman works hard to make sure our dredging budget is secured annually and this year he was able to get $7.2 million allocated to catch up on maintenance of shipping channels away from the entrance.
The inability to maintain deep-draft shipping in winter is highly undesirable, causes loss of revenue for private shippers and for the Humboldt Bay Harbor, Recreation and Conservation District, and poses a risk to fishermen crossing the bar. Some in the public have stated that the Harbor District is negligent because the shoaling was not addressed immediately. It has even been suggested that sediment near the entrance could have been removed in advance of winter storms to prevent its transport into the entrance.
This shows a fundamental lack of understanding of the magnitude of the sediment delivery problem and the reality of budget limitations.
The amazing sediment delivery engine that fills the bay entrance is the Eel River. Sediment delivery to the Eel River increased exponentially as a result of the 1964 flood, with deposits estimated at 40-60 feet deep at Dyerville according to the U.S. Geologic Survey (USGS).
The river can be thought of as a giant conveyor belt that delivers huge quantities of sediment to the ocean off the mouth. The heavy rains storms, which cause the river’s rise, almost always come from the south and set up what geologists call littoral drift in the near-shore ocean toward the north. This causes the sediment blown out of the river to travel parallel the shore and into the mouth of Humboldt Bay. Depths at the entrance can decrease by 10 feet or more in one storm event. This last winter Eel River flow approached or exceeded 100,000 cubic feet per second on three occasions pushing a huge sediment load out the mouth and towards Humboldt Bay. Ocean waves of 38-42 feet in late March forced the sediment into the mouth and created acutely hazardous conditions.
The Harbor District contacted the Army Corps as soon as it had information on the shoaling problem.
The Army Corps’ larger dredging ship the Essayons was in Hawaii, and the seas off the mouth of Humboldt Bay were too rough for the dredge to operate. When the Essayons arrived in the first week in May, ironically the shoaling at the entrance had made it too shallow for the large dredging ship to operate. Within 10 days, the smaller dredge Bayport to began the dredging project. The Essayons came back when depths were sufficient for its operation, and will return in September to finish the inner reach.
Calls for emergency action in the winter or for “pre-dredging” to remove sediment from the ocean to prevent shoaling do not take into account that our access to Army Corps of Engineers services is limited and the amount of sediment pouring out of the Eel River is virtually unlimited.
If the Army Corps sends the dredge in winter when it is too rough to operate, the charge rate for the ship is approximately $150,000 per day whether it is working or not. If the entrance were dredged in winter, then refilled on subsequent storms, we would have no budget to clear it later in spring. Dredging material between the bay entrance and the Eel River before winter storms would hardly change the filling at all and would be a complete waste of money.
As we work on long term solutions with the Army Corps to entrance shoaling, the Harbor District is also asking Congressman Huffman to help get the USGS to study Eel River sediment generation. Hopefully more sensitive land use practices will result in diminished sediment supply from the Eel River in the future, but the current over-supply is likely to continue for the next several decades at least.
The Harbor District would like to thank the Army Corps and Congressman Huffman for helping us cope with the continuing problem of entrance shoaling and the public should also be grateful.
Patrick Higgins is the chairman of the Humboldt Bay Harbor, Recreation and Conservation District commission.
