Analysis of Variance of Flood Events on the U.S. East Coast: The Impact of Sea-Level Rise on Flood Event Severity and Frequency

By Paul Homewood



This new paper is relevant given recent events:




Schedel, J.R., Jr. and Schedel, A.L., 2018. Analysis of variance of flood events on the U.S. East Coast: The impact of sea-level rise on flood event severity and frequency.

This is an investigation to quantify the severity and frequency of coastal flood events on the U.S. East Coast. Flood events are defined as instances during which the water level exceeds a predetermined threshold. An examination of monthly water-level data from 13 locations on the U.S. East Coast shows an increasing mean sea-level trend. Analysis of variance was used to compare the frequency of flood events. At all 13 locations, flood events were compared to established moderate and minor flood stages in the pre-1990 and post-1990 time frames. Flood stages are defined as water-level heights associated with various levels of flooding. For all locations, compared to absolute water heights based on a fixed datum, these flood stages were exceeded more frequently today than in the past. However, when the effects of sea-level rise were negated, flood events were shown to occur at similar rates today as in the past. Flood events that were significantly higher than the mean sea level occurred with the same frequency over the past century. Based on absolute water levels, flood events are more severe and more frequent than in the past. However, if the effects of sea-level rise are negated, flood events show little to no change in severity or frequency. Coastal flood events are starting from a higher baseline height because of sea-level rise. Thus, the same severity of a flood event today reaches a greater absolute height than an identical flood would have reached 50 or 100 years ago.


Common sense tells us that higher sea levels will mean floods are now slightly higher on average than they were before. But the key message is that, discounting the sea level factor, coastal flood events have not changed in terms of frequency or severity over the period of the study.


October 6, 2018 at 05:54AM

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