ITHACA, N.Y. —This weather history piece builds off of the hurricane article last week, which discussed the historical context of hurricanes in the Ithaca area. There’s no doubt Ithaca’s seen some sizable deluges from tropical storms and hurricane impacting the region. But when it comes to the most disastrous local floods, their sources are anything but tropical.

The two worst floods in Ithaca occurred quite a long time ago – in 1857 and 1935. There have also been more recent events that people can remember – the severe flooding in October 1981, and the ice jams that threatened to flood Fall Creek just a few years ago. The flood control channel down by Cass Park is there for a reason, even if it is so silted-up at this point that it poses a major risk to the city and its low-lying neighborhoods.

The 1857 flood was massive. Keep in mind, it hails from a much different time in Ithaca’s history, before the colleges, and when the village itself had a few thousand people, mostly clustered along dirt roads that led to a cluster of shops and stables in what is now downtown. Although sources are somewhat lacking, the downtown area was underwater for several weeks. This was before the era of effective flood control, and since the city of Ithaca is surrounded by steep hills on three sides and a lake on the fourth, the drainage system is about as far from optimal as one can get. Add to that some relatively impervious fine-grained soils, and it becomes a big soggy problem.

Local flooding tends to be spurred by two types of events – this first, winter floods, are often triggered by a combination of downpours during a sudden winter thaw that melts and weakens the ice. The ice may collapse and pile up as ice jams in narrow waterways or against bridges, damming flow and causing waters to overflow banks. The second are summer floods set up by convection, “pop-up” thunderstorms. The 1857 and 1935 floods were warm-season, convective events – June 1857 and July 1935, respectively.

The flood of June 17, 1857 seems to be the result of a highly localized warm-season precipitation event directly on the Six Mile Creek watershed, in what may have been a wet microburst or a cloudburst type of event. Both tend to be local and related to intense thunderstorm activity. They are notoriously difficult to forecast, and microbursts are one of the biggest reasons planes won’t land near thunderstorms. The raging torrent washed out two dams, whose debris then slammed into the Aurora St. bridge, collapsing its stone arches and sending the whole shebang surging through the town. Heck, you can quote Ezra Cornell on that one.

Some measures were taken to improve flood control, including more numerous or bigger dams. Beebe Swamp and Pond were turned into Beebe Lake by a larger Triphammer Falls Dam in 1898. Yet, the area still had flooding issues, including events in December 1901 and June 1905. However, nothing quite prepared Tompkins County for the disaster that was the July 1935 flood, the worst single inundation in the county’s history.

The July 8, 1935 flood originated with a large thunderstorm complex known scientifically as a “mesoscale convective system”.  A typical summer thunderstorm is a few minutes of heavy rain, followed by lighter rain as the storm moves on, and eventually it tapers off and things dry out. In a thunderstorm complex, they may undergo “training“, which is one storm, after another, after another, passing over the same spot like the cars of a freight train. All those downpours can add up very quickly. That is what happened on the night of July 7th into July 8th.

The 24-hr. rainfall total of 7.9 inches in Ithaca (the weather station was on Cornell’s Ag Quad back then) is impressive. The local creeks almost immediately began to flood, and as drainage brought more water into the streams, they began to tear away at their banks, before flooding Cayuga Lake downstream. Damage occurred throughout the county, from homes washed away in Enfield to buildings being swept off their foundations in Trumansburg. A passenger train was stranded, and all the train tracks in the county were washed out or impassable due to debris. Most state parks in the area were badly damaged and downtown Ithaca was once again flooded. Cornell’s Barton Hall was used as an emergency shelter for almost seven hundred people.

Eleven people lost their lives in Tompkins County as a result of the flood (with 52 being lost in total, and $26 million in damage [1936 dollars, equivalent to $466 million today]). The damage to Ithaca was about $1.8 million in 1936, which adjusts for inflation to about $32 million in 2017 dollars.

Granted, there are few folks around today who remember the flood of 1935. 82 years is a long time. However, most Ithacans can remember a flood that was almost as bad – October 27-28th, 1981.

As with 1935, the source of the prodigious rains was a series of intense, training thunderstorms that had established themselves over the Southern Tier and Central New York – a bit late in the year, but weather doesn’t always heed to the calendar. A cut-off low-pressure system stalled west of the region, pumping in warm air, southern moisture and creating the instability needed to develop the storms. The rainfall amount in the ’81 storm was substantially less 1935’s record – 5.08 inches. But 4.4 inches fell in a six-hour period, a much faster rate than the 2.96″ per six hours recorded during 1935’s wettest span. There had already been almost four inches of rain that October, and the ground was thoroughly saturated before the first storms came.

October 1981. Dryden’s Freese Road bridge hangs in the air over Fall Creek after its north supports were washed away. Photo property of Laurie Snyder.

In downtown Ithaca, Six Mile Creek became a raging torrent or murky water, tearing out the retaining wall and causing a vacant bakery next to Hickey’s Music Store to partially collapse. Footbridges and hillside stairs were washed away into the rapids, the Tioga Street bridge was wiped out by Cascadilla Creek, and most major roads were badly damaged. In Southside, Northside and Fall Creek, the water piled up thigh-deep, and dozens had to be evacuated.

Perhaps worst off was the village of Dryden, which found itself four feet underwater and without a clean water supply; a photo from that day’s Ithaca Journal shows firefighters navigating the frothy waters between Main Street’s submerged cars. Beyond Tompkins, a Conrail train was washed off its tracks in Allegheny County, floods inundated Syracuse, and landslides were reported in the city of Cortland.

“Just a two-hour rainfall of 2.25 inches would have caused the flooding,” said Cornell University meteorologist Douglas Paine at the time. “Any time this area gets that rate of rainfall, there is the potential for flooding.” On that note, the flash flooding in Dryden and Lansing at the Ithaca Mall this past July was a little over 2 inches.

As with every major flood, the 1981 event led to changes big and small – the Virgil Creek Dam was built in Dryden, there’s been a big push to de-channelize streams so that they flow slower, and newer buildings have to be built with their ground floors above the USGS 100-year flood line. But with time, there’s always the risk of slipping into complacency, as noted by the Times recently with their coverage of the dredging, or lack thereof, for the inlet.

Floods have been a part of the local history since before the first pens were put to parchment. While they’re not likely to be of Biblical scale, there’s something to be said about flood mitigation and proactive engineering for the next “big one”. Have a look at the falls after the next downpour, and take a moment to think that it has been and can be much worse.

Our deepest thanks to Rich Entlich for generously lending his copies of The Ithaca Journal.

Brian Crandall

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.com.