Temporary flood marks proposal: What we learned after losing the baroque artifact from Cracow, Poland

Abstract

For centuries flood marks have been used as a way to preserve the memory of extreme events. In many cities around the world they are considered a cultural heritage and a reminder of historic flood disasters. Their timeless message has endured the ravages of nature over the centuries, but without adequate protection, they risk being irretrievably lost, and with them an important historical message. In Cracow, 21 such artifacts have survived to this day, with the oldest dating back to the 16th century. Yet, the fundamental problem relates to their lack of cataloging and surveying to date. As part of the presented project, we surveyed the preserved marks and recreated the exact location of a lost baroque flood mark using the photogrammetric method, based on preserved photos and images available on Google Street View. Subsequently, this data was uploaded into the public database of the Open Hydrology project. In order to facilitate the reconstruction of flood information in the future, we propose an innovative way of using smartphones to register temporary flood marks. The conclusion from tests on several popular smartphone models suggests the proposed guidelines allow for an inexpensive and quick creation of flood marks with an accuracy of 10 mm. The data collected in a digital format can be used to raise public awareness of floods and is easy to disseminate. Historical flood marks are usually represented in the form of plaques, but are difficult to produce on a mass scale, yet appeal to the imagination. Their digital substitutes can be temporary flood marks photographed with smartphones, so their associated cost is negligible. Furthermore, because they are taken immediately after the flood and not during it (unlike ordinary flood photography), they do not pose a threat to people's safety. The method proposed in this article takes the form of simple guidelines and can be successfully applied for both the quick creation of new temporary flood marks, and for documenting traditional historical marks.