ITHACA, N.Y. — When hearing about the flooding damages to Houston on the news, and the hurricanes that ravaged much of the Caribbean and southeastern United States the past few weeks, it’s easy to think that in the much higher latitudes of Ithaca, there’s little risk here. After all, hurricanes are by definition tropical cyclones, and Ithaca is many things but tropical sure as heck isn’t one of them.

However, tropical storms and hurricanes do pose a local risk.

Ithaca has seen some tropical-born activity over the years. Typically, the storm has weakened into a remnant low or turned extratropical (meaning that a storm transitions into a typical mid-latitude storm system — “cold-core” low-pressure areas vs. “warm-core” hurricanes) by the time the cyclone has passed into and over the region. 1954’s Hurricane Hazel, for instance, passed over as an extratropical system with winds still at hurricane strength, but because the Allegheny Mountains wrung out most of the moisture from the east side of the storm, the region was mostly spared (Toronto was not so lucky). Wikipedia identifies 84 tropical cyclones that have impacted the state of New York, and as one might imagine, the majority of these have affected New York City and Long Island.

When a storm transitions to an extratropical state, it doesn’t just stop raining. Occasionally, if the conditions are favorable, with a moist environment and perhaps some topographical effects coming into play like hills and mountains, the rain can be heavy and prolonged, resulting in flooding. This is exactly what happened with Hurricane Agnes, and more recently with Tropical Storm Lee.

Hurricane Agnes at its Florida landfall, June 19th, 1972. Public domain image courtesy of NOAA.

Hurricane Agnes was the first named storm of the 1972 hurricane season. As a tropical cyclone, Agnes wasn’t particularly special; about the most unusual thing was that it was a June hurricane, a bit early in the year since the first hurricane usually isn’t until early August.

Agnes formed off the eastern coast of the Yucatan Peninsula of Mexico, and moved directly north through the gulf, strengthening into a Category 1 storm with sustained one-minute winds of 85 mph. The hurricane made landfall over the Florida Panhandle, moved northeast into Georgia while weakening into a tropical depression, and then passed over the Atlantic. While over the ocean, Agnes redeveloped into a tropical storm before swinging back west and making a second landfall near New York City with 70 mph winds. Agnes merged with a non-tropical mid-latitude low on June 23, and this combined system slowly passed over the region until finally moving away late on the 25th.

This was a very dangerous combination. The combined system had large amounts of tropical moisture from Agnes, and was slow moving thanks to the non-tropical low. Therefore, rains of 6 to 12 inches occurred over 2 days, with the highest recording at 19 inches. For perspective, that’s three months of this region’s normal rainfall, in just 48 hours. The resulting flooding for Pennsylvania and New York was disastrous. In Pennsylvania, 50 lives were lost and $2 billion in damage (1972 dollars) was incurred. The governor had to flee his deluged mansion, and downtown Wilkes-Barre was under nine feet of water.

As for New York, the hardest-hit areas were a swath from Olean east to Elmira and Corning. In Elmira, the raging Chemung River destroyed or badly damaged most of the downtown area. One of Elmira’s industrial drivers was its railroads, but the railways were washed out by the storm and the bill for repairs was so high that the railroad companies opted for bankruptcy instead. Similar destruction was wrought onto Corning.

In Ithaca, where the rainfall came out to about 7 inches, several bridges in the city and in nearby Brooktondale were washed out and the low-lying areas near several of the local streams were flooded. The Cascadilla Gorge trail was wiped out and required a year and half of work to reopen and Cayuga Lake rose enough to flood and damage the facilities at Stewart Park. Thankfully, Cornell and Ithaca College were out for the summer, and neither sustained major damage. The final toll in New York was 24 deaths and $700 million in damage (1972 dollars).

More recently, the Southern Tier dealt with the remnants of 2011’s Tropical Storm Lee. Lee’s setup was somewhat different — 2011 was a wet summer, and hardly a week before, the region was soaked with rains by Hurricane Irene as it barreled through the eastern part of the state. Lee made landfall as a large, strong tropical storm in Louisiana. After transitioning into an extratropical system, its decaying but moisture-laden circulation was channeled northeastward along a strong cold front. It had the instability and rain of a slow-moving cold front, with the vast moisture feed of a tropical system. Once again, a bad combination. From Sept. 6 to 8, rain exceeded 12 inches in places, on top of already saturated soil. All that water has to go somewhere.

This time, it was Ithaca’s neighbors to the south and east that fared the worst. In Binghamton’s Broome County, 20,000 people were forced to flee their homes, while downtown Binghamton was buried under feet of murky brown water. I-88 was cut off by a mudslide. In Tioga County, 95 percent of Owego was underwater, as the Susquehanna River topped its banks. 7,000 properties were damaged. Property losses in Broome and Tioga alone totaled nearly a billion dollars, and two people lost their lives.

Tompkins County picked up 4 to 7 inches, increasing from northwest to southeast. Several local roads and East Hill Plaza were flooded, and normally placid waterfalls turned into gushing torrents. But once again, Ithaca fortunately dodged the worse of it.

While Ithaca is far from the action of the tropics, it’s not necessarily immune to the passage of tropical cyclones. Probability says that Ithaca’s risk will eventually result in another major flooding event, like receiving a bad hand in poker but with a much bigger wager on the line. Ithaca and Tompkins County have had devastating floods, in 1857 and 1935. But neither one of those had tropical influence.

Boiling it down to a matter of probability, eventually Tompkins County will be in the crosshairs of the flooding rains brought on by a tropical storm or hurricane, if not the storm itself. It’s something that emergency services and planners and homeowners have to aware of and keep in the back of their mind. While it’s not comfortable to think about as one watches the reports coming out of Houston, Florida or the Caribbean, someday that may be Tompkins County in the news, and it’s better to proactive plan and be prepared now, than be caught off guard later.

Brian Crandall

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