Determining Storm Surge Return Periods: The Use of Evidence of Historic Events

Kristine S. Madsen, Carlo Sass Sørensen, Torben Schmith, Jacob Woge Nielsen, Per Knudsen

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    Abstract

    Storm surges are a major concern for many coastal communities, and rising levels of surges is a key concern in relation to climate change. The sea level of a statistical 100-year or 1000-year storm surge event and similar statistical measures are used for spatial planning and emergency preparedness. These statistics are very sensitive to the assessments of past events, and to future sea level change.
    The probability of a major storm surge from the Baltic Sea hitting the Copenhagen metropolitan area is officially determined by the Danish Coastal Authority based on tide gauge records. We have a long history for tide gauge measurements, with 120 years of data available for the calculations. However, the oldest of these tide gauge stations was set up after a major storm surge in 1872, and no events of similar severity have occurred since.
    Including the evidence of the historic events from the 18th century changes the return period statistics, with a best estimate of a 100 year event changing from 1.5 meters (Sørensen et al. 2013) to 2.6 [2.2 – 2.8] meters (present study) in Køge just south of Copenhagen. Thus, with the tide gauge-based statistics, the storm surge on January 4 2017 was a 100 year event, but with the revised statistics using historic evidence, much larger events can be expected.
    Further, we assess the very large impact of sea level rise on the storm surge statistics. As an example, according to the official statistics of southern Copenhagen, the flooding of a present day 100 year event will statistically occur every 10 years with just 27 cm of mean sea level rise.
    Original languageEnglish
    Publication date2017
    Number of pages1
    Publication statusPublished - 2017
    EventInternational WCRP/IOC Conference 2017: Regional Sea Level Changes and Coastal Impacts - New York, United States
    Duration: 10 Jul 201714 Jul 2017

    Conference

    ConferenceInternational WCRP/IOC Conference 2017: Regional Sea Level Changes and Coastal Impacts
    Country/TerritoryUnited States
    CityNew York
    Period10/07/201714/07/2017

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