One of these more than a dozen reference points identified by the historian is the corner of the Gasthaus Krone, a hotel located directly opposite Schifflaende, the Basel shipping pier. This reference has been used in comparative descriptions over the centuries: In 1506, the flood reached "into the tavern," in 1664, it reached "the front door" and in 1764, the flood "didn't quite reach the corner of the tavern." Fortunately, local journalists referred to the "Kroneneck" when writing an article on a flood well into the 19th century, when the Rhein's water levels and effluent were measured with instruments. The parallel use of the two recording systems allowed Wetter to convert the descriptions into numeric values, and he eventually managed to compile an unprecedented data volume: the reconstruction of flood occurrences over 743 years.
One of the side benefits of Wetter's hydrological model is that it also provides climate historians with quantitative data on the volumes of water. Thus, researchers may for the first time directly compare the floods from pre-instrumental and instrumental times. These research findings are not only of scientific interest. Insurance companies for example, who calculate premiums based on so-called once-in-a-century events, are very interested in comparative data that reaches that far back. Only an analysis of flood disasters over the centuries, allows researchers to judge whether the incidence has indeed increased over the past decades. These questions are, of course, also pertinent to current discussions about the safety of Swiss nuclear power plants.
Wetter himself is more than happy with his results. "First, I was simply fascinated that my work could contribute to a better understanding of climate change. Today, I'm not just fascinated, but I am also aware of the incredible potential of historic climatology. And, at this point, we're only at the very beginning of all analyses that are possible."
(2011)