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Question: I am enrolled in a career class at my school and for my final project I studied and graphed the water levels of the Susquehanna River in Owego. It seems that the river waters are rising higher and that flooding is increasing in frequency. Is this so and will Owego be a safe place to live in five, ten and twenty years from now?
Record-setting floods in 2006 and 2011 certainly prompt us to ask questions about the frequency of floods, whether floods of this size--or even larger--can occur in the future (and how soon), and whether we're getting more frequent large floods. Before trying to address these issues, let me first point out that floods are, in fact, random events; with few exceptions, the occurrence of one flood provides no predictive value about long it will be before a flood of similar or larger size will occur in the future.
The floods along the Susquehanna River over the last 2 decades have indeed been more frequent than in the preceding several decades. Is this an indication of a change in flood frequency and size? Perhaps--and perhaps this is the result of the changing climate. But we have only about 100 years of direct flood measurements in the Southern Tier (and far less in places like Owego), and it's simply not possible with the available data to say whether this recent pattern is truly unusual in the longer term.
Have the floods been progressively larger in recent years? It depends on where you are. The 2006 flood was larger in Conklin, upstream of Binghamton, than the 2011 flood. Yet from Binghamton downstream along the Susquehanna, the 2011 flood was larger--and the extremely heavy rain between Binghamton and Owego produced a particularly devastating flood in the village of Owego (as well as in several places in the Triple Cities). So, the floods have not been consistently higher and larger everywhere in the region.
What does all of this mean for the safety of places like Owego? Large floods like 2011 have a certain likelihood of occurring in any given year, even if they've just occurred. What is called the "100-year flood" actually has a 1% chance of occurring in any given year--even if it occurred last year (and the 2011 flood was a rarer flood than, on average, once in 100 years). So it means that flood-prone areas remain at risk. And we can't say Owego is (or isn't) going to be safe from floods for the next 10, 20, or even 100 years. Nor can we rule out larger floods in the future. The reality is that the Susquehanna River is flood-prone, and anyone living near the river, at low to moderate elevations above the river, is at risk from future floods.
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