"It might be thought that the greatest flood would be caused by a heavy, warm rain falling on frozen ground covered with snow ; but the greatest flood in the Merrimack river, of which there is any knowledge, certainly for more than one hundred and fifty years, was in the month of October, and was caused by a continuous, southerly, heavy rain of about forty-eight hours' duration."
- James B. Francis
It was perhaps this insight, along with the amazing engineering that effectively reversed the flow of the last major canal in a massive network that led to a stopgap measure that has saved untold damage and likely lives in the City of Lowell during multiple flooding events along the Merrimack River.
The Great Gate is at the left. It would be closed to prevent flood water entering the North Canal - photo credit: Library of Congress
The City of Lowell is widely considered the place where the Second Industrial Revolution, if not launched, certainly took firm footing and went on to serve as a template other communities around New England would mimic, albeit with different scale and specialties. Core to the success of Lowell was it’s location along the Merrimack River and the network of canals that were built beginning in the 1790’s and continuing for decades, culminating in the opening of the Northern Canal in 1847. All told, the Lowell Power Canal system remains the largest in the U.S. at over five miles long, producing an estimated 10 thousand horsepower. It is simply an amazing example of engineering.
One component of this system that stands out among many is the Great Gate that was designed by Chief Engineer James B. Francis. Built in 1850 at the entrance of the 4,374 feet long, 20-feet wide, 100-feet deep Northern Canal to prevent the Merrimack River flooding downtown Lowell, it was widely ridiculed as a failure, branded with the moniker “Francis’ Folly”. Two years later the gate was lowered and proved effective by protecting the city of Lowell from devastation when the Merrimack rose to 60.6 feet. The Great Gate was lowered again during the Great Flood of 1936 when the river reached a record 68.8 feet at that location, again during the 1938 New England Hurricane (60.6 feet). The gate was damaged by vandalism in the 1970’s and when repaired, upgrades were made. Lowered again during the Mother’s Day Flood of 2006 and one more time, in 2007, the Great Gate has prevented incalculable damage to the City of Lowell.
Map of the Lowell Canal System - credit: Wikicommons
High-water mark carved into the granite wall of the Great Gate - photo credit: Library of Congress
Interestingly, later on in his career, James Francis, as a member of the American Society of Civil Engineers, was an investigator into the 1874 Williamsburg Dam failure on the Mill River, a story told in wonderful detail in the book written by Elizabeth Sharpe, In the Shadow of the Dam, The Aftermath of the Mill River Flood of 1874.
No doubt, the Great Gate will be ready again the next time New England Floods.
Modern-day view of the entrance of the North Canal at the Merrimack River
Francis, J. B. (1886). Prevention of Floods in the Valley of Stony Brook: A Report by a Commission Consisting of James B. Francis, Eliot C. Clarke, Clemens Herschel. United States: Rockwell and Churchill, City Printers.
Francis, James B.; et al. (1874). "The failure of the dam on Mill River". ASCE Transactions. 3 (4): 118–122.
Historic American Engineering Record, C., Merrimack Manufacturing Company, Francis, J. B., Proprietors Of The Locks & Canals On The Merrimack River, Jackson, J., Tyler, J. [...] Malone, P. M., Boucher, J., photographer. (1968) Pawtucket Canal, Guard Locks, Lowell, Middlesex County, MA. Lowell Massachusetts Middlesex County, 1968. Documentation Compiled After. [Photograph] Retrieved from the Library of Congress, https://www.loc.gov/item/ma1174/.
National Park Service History eLibrary. (n.d.). at http://npshistory.com/publications/lowe/cri.pdf
Sharpe, Elizabeth M. (2007). In the Shadow of the Dam, The Aftermath of the Mill River Flood of 1874. Simon and Schuster