I have driven past a bulkhead in Lake Pontchartrain at the north end of Upper Guide Levee Road. We pass it often when heading west. I can only guess that it's some type of jetty used to divert the Mississippi River's water farther from shore. Do you have any information on the old structure?
The Bonnet Carre Spillway in St. Charles Parish, between the towns of Montz and Norco, has been diverting excess Mississippi River water into Lake Pontchartrain since 1931. Authorized by the Flood Contol Act of 1928, it was first opened during a flood in 1937 and again for floods in 1945, 1950, 1973, 1975, 1979, 1983, 1997 and 2008. The U.S. Army Corps of Engineers (USACE) also partially opened the spillway in 2011 after heavy rains in the Mississippi and Ohio river valleys.
Two main parts help the spillway operate: a mechanically controlled barrier at the east bank of the Mississippi River and a floodway nearly 6 miles long in which the water travels to Lake Pontchartrain. This floodway is bordered by an upper guide levee and a lower guide levee, which extend into the lake so the water from the Mississippi River is directed beyond the lake's immediate shoreline.
The bulkheads at Bonnet Carre are large and substantial because they have to withstand the force of river water, which can reach speeds of roughly 1.9 million gallons per second during full operation, says Ricky Boyett of the USACE. On the upper guide levee there are the ruins of an old wooden structure that dates back to the construction of the spillway.
St. Charles Parish has updated the lower guide levee for visitors' recreational activities, including crabbing, crawfishing, waterskiing, picnicking and birding.