Cultural Ecosystem Services of Geodiversity: A Case Study from Stránská skála (Brno, Czech Republic)

The concept of ecosystem services developed in the second half of the 20th century, and the Millennium Ecosystem Assessment was crucial for its acceptance. This assessment identified the services that ecosystems provide to society, but geodiversity (as an indispensable component of ecosystems) was somewhat underestimated. At present, geodiversity is intensively used by human society and it provides numerous services including cultural as a resource for tourism, recreation, as a part of natural heritage, and to satisfy matters of spiritual importance. The main purpose of this paper is to present the geocultural issues of Stránská skála (a limestone cliff with caves and an anthropogenic underground) in Brno (Czech Republic) and to evaluate the cultural ecosystem services of geodiversity by using the abiotic ecosystem services approach. This assessment of cultural ecosystem services of the Stránská skála enables the identification and description of the functions and services which are provided by geodiversity and confirms the high cultural and geoheritage value of the site.

Multi-Channel Ground-Penetrating Radar Array Surveys of the Iron Age and Medieval Ringfort Bårby on the Island of Öland, Sweden

As a part of the project “The Big Five”, large-scale multi-channel ground-penetrating radar surveys were carried out at Bårby ringfort (Swedish: borg), Öland, Sweden. The surveys were carried out using a MALÅ Imaging Radar Array (MIRA) system and aimed at mapping possible buried Iron Age and Medieval remains through the interior in order to better understand the purpose of the fort during its periods of use. An additional goal was to evaluate the impact of earlier farming on the preservation of the archaeological remains. The data provided clear evidence of well-preserved Iron Age and Medieval buildings inside the fort. The size and the pattern of the Iron Age houses suggest close similarities with, for example, the previously excavated fort at Eketorp on Öland. Given the presence of a substantial cultural layer together with a large number of artefacts recovered during a metal detection survey, it is suggested that Bårby borg’s primary function during the Iron Age was as a fortified village. The Medieval houses partly cover some of the Iron Age buildings. They are placed in a U-shape with an open square in the middle facing the edge of a limestone cliff. As in the case of Eketorp, it is suggested that the activities during Medieval times changed, but the precise purpose of the Medieval Bårby settlement is still a question open for debate. Future targeted archaeological investigations are needed in order to better understand its purpose. Rescue excavations may also be necessary, as the western steep cliff ledge is eroding and the well-preserved archaeological remains are at risk of being destroyed.

Influence of meteorological factors on rockfall occurrence in a middle mountain limestone cliff

The influence of meteorological conditions on rockfall occurrence has been often highlighted, but knowledge of it is still not sufficient due to the lack of exhaustive and precise rockfall databases. In this study, rockfalls have been detected in a limestone cliff by annual terrestrial laser scanning, and dated by photographic survey over a period of 2.5 years. A near-continuous survey (one photo every 10 min) with a wide-angle lens has made it possible to date 214 rockfalls larger than 0.1 m3, and a monthly survey with a telephoto lens has dated 854 rockfalls larger than 0.01 m3. Analysis of the two databases shows that the rockfall frequency can be multiplied by a factor as high as 7 during freeze–thaw episodes and 26 when the mean rainfall intensity (since the beginning of the rainfall episode) is higher than 5 mmh−1. Based on these results, a three-level scale has been proposed for predicting the temporal variations of rockfall frequency. The more precise database and freeze–thaw episode definition make it possible to distinguish different phases in freeze–thaw episodes: negative temperature cooling periods, negative temperature warming periods and thawing periods. It appears that rockfalls occur more frequently during warming and thawing periods than during cooling periods. It can be inferred that rockfalls are caused by thermal ice dilatation rather than by dilatation due to the phase transition. But they may occur only when the ice melts, because the cohesion of the ice–rock interface can be sufficient to hold the rock compartment which has been cut.

Influence of meteorological factors on rockfall occurrence in a middle mountain limestone cliff

The influence of meteorological conditions on rockfall occurrence has been often highlighted, but its knowledge is still not sufficient due to the lack of exhaustive and precise rockfall data bases. In this study, rockfalls have been detected in a limestone cliff by annual terrestrial laser scanning, and dated by photographic survey during 2.5 years. A near-continuous survey (1 photo each 10 mn) with a wide-angle lens have allowed dating 214 rockfalls larger than 0.1 m3, and a monthly survey with a telephoto lens, dating 854 rockfalls larger than 0.01 m3. The analysis of the two data bases shows that the rockfall frequency can be multiplied by a factor as high as 7 during freeze–thaw episodes and 26 when the mean rainfall intensity (since the beginning of the rainfall episode) is higher than 5 mm h−1. Based on these results, a 4-level scale has been proposed for predicting the temporal variations of hazard. The more precise data base and freeze–thaw episode definition make it possible to distinguish different phases in freeze–thaw episodes: negative temperature cooling periods, negative temperature warming periods and thawing periods. It appears that rockfalls occur more frequently during warming and thawing periods than during cooling periods. It can be inferred that rockfalls are caused by thermal ice dilatation rather than by dilatation due to the phase transition. But they may occur only when the ice melt, because the cohesion of the ice–rock interface can be sufficient to hold the rock compartment which has been cut.

Brief communication"Estimating rockfall frequency in a mountain limestone cliff using terrestrial laser scanner"

Using terrestrial laser scanner, 344 rockfalls larger than 0.05 m3 have been detected for a period of 1180 days, in a thinly bedded limestone cliff of width 750 m and height 200 m. The complementary cumulative distribution of the rockfall volume is well fitted by a power law, with an exponent b of 0.75 ± 0.04. In order to compare the rockfall frequencies in different geological contexts, a rockfall activity parameter has been defined, which is the number of rockfalls larger than 1 m3, which occur per century and per hm2.