Google “global warming” and “flooding,” and you’ll find 3.96 million sites where these topics are discussed together. The overwhelming majority of sites, it’s safe to assume, warn of global warming-induced increases in the frequency and severity of flooding.

And if you’ve paid any attention to the global warming debate, you know that alarmists predictably predict that climate change impacts are even worse than they previously predicted.

But, as noted in an earlier post, a recent study based on global tide gauge data (Houston and Dean, 2011) found that the rate of sea-level rise over the past 80 years did not accelerate and, in fact, slightly decelerated. Just the opposite of what we usually hear.

A new study (Bouzotias et al., 2011) by scientists with the National Technical University of Athens brings more good news: Discharge records of the world’s river basins show a decreasing trend in floods over the past 50 years.

The researchers examined extreme floods at 119 stations worldwide with records longer than 50 years. In particular, they analyzed “trends and persistence (else known as Hurst-Kolmogorov dynamics), which characterizes the temporal streamflow variability across several time scales.”

Noting the “common belief” that “the severity, frequency and consequences from floods have been increased in recent years,” the Bouzotios team sought to determine “whether there is a general increasing tendency worldwide, especially considering the last climate period (after 1970) when the effects of global warming are believed to be apparent.”

Here’s what they found:

Analysis of trends and of aggregated time series on climatic (30-year) scale does not indicate consistent trends worldwide. Despite common perception, in general, the detected trends are more negative (less intense floods in most recent years) than positive. Similarly, Svensson et al. (2005) and Di Baldassarre et al. (2010) did not find systematical change neither in flood increasing or decreasing numbers nor change in flood magnitudes in their analysis.