Preprints
https://doi.org/10.5194/egusphere-2022-223
https://doi.org/10.5194/egusphere-2022-223
 
17 May 2022
17 May 2022

Reliability of flood marks and practical relevance for flood hazard assessment in south-west Germany

Annette Sophie Bösmeier1, Iso Himmelsbach2, and Stefan Seeger3 Annette Sophie Bösmeier et al.
  • 1Chair of Geomorphology and Recent Morphodynamics, University of Freiburg, Freiburg, 79085, Germany
  • 2independent researcher: Gießenstraße 11, Freiburg, 79104, Germany
  • 3Chair of Hydrology, University of Freiburg, Freiburg, 79098, Germany

Abstract. Flood marks are rarely utilized in hazard assessment, mainly because of a lack in data availability, accessibility, and mistrust in their reliability. Challenging these common assumptions, we present an approach for evaluation and practical utilization of flood marks by the example of the Kinzig river, a Rhine tributary from the Black Forest with a history of severe floods. We combined written documents on flood marks with field mapping at three study sites and collected 89 marks – about 50 % of them still preserved – which refer to ≥ 15 large floods between 1824 and 1991. The inclusion of a detailed historical mark survey allowed to identify and assess changes over time: they extend from small (+/- 15 cm) imprecisions in mark heights to considerable uncertainties in position, height, and displayed date for some modified marks. Plausibility checks with further data nevertheless demonstrated an overall good consistency. We then juxtaposed these marks with the current, modeled flood hazard maps. A wide agreement is apparent, in that the large majority of the marks are situated at probable heights and within the modeled flooding area associated with extreme floods. For the few exceptions, we see plausible and historically sound reasons in changed local hydraulic conditions by flood protection walls, exceptional processes during a massive ice jam, and possibly also a local underestimation of hazard along Kinzig river tributaries. Overall, this study highlights (1) the broad availability of flood mark data, both on a larger spatial scale and with regard to already vanished marks, and (2) the significance of the marks, verified by further data; and (3) it also demonstrates the possibility of a straightforward inclusion in hazard assessment. We thus encourage the systematic collection, maintenance, and integration of flood marks in a responsible risk management, not least regarding their value in the wider context of risk awareness and memory.

Annette Sophie Bösmeier et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-223', Neil Macdonald, 02 Jun 2022
  • RC2: 'Comment on egusphere-2022-223', Anonymous Referee #2, 24 Jun 2022

Annette Sophie Bösmeier et al.

Annette Sophie Bösmeier et al.

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Short summary
Encouraging a systematic use of flood marks for a more comprehensive flood risk management, we collected a large number of marks along the Kinzig, south-west Germany, and tested them for plausibility and temporal continuance. Despite uncertainty, the marks appeared to be an overall consistent and practical source that may also increase flood risk awareness. A wide agreement between the current flood hazard maps and the collected flood marks moreover indicated a robust local hazard assessment.