Increased gully activity induced by short-term human interventions – Dendrogeomorphic research based on exposed tree roots. (September 2018)

• Record Type: Journal Article
• Authors: Tichavský, Radek; Kluzová, Olga; Břežný, Michal; Ondráčková, Lenka; Krpec, Petr; Tolasz, Radim; Šilhán, Karel
• Is Part Of: Applied geography. Volume 98(2018)
• Page Start: 66
• Page End: 77
• Publication Date: 2018-09
• Subjects: Gully erosion -- Dendrogeomorphology -- Root exposure -- Triggering rainfall -- NE Czechia; Geography -- Periodicals; Human geography -- Periodicals; Human ecology -- Periodicals; 910
• DOI: 10.1016/j.apgeog.2018.07.008
• Languages: English
• ISSNs: 0143-6228

Abstract

Abstract: The recent acceleration of gully erosion caused by environmental factors and human impacts has led to an enhanced demand for applied research in risk-prone areas worldwide. We investigated the dynamics of gullies that have recently threatened dwellings and railways in the foreland of the Eastern Sudetes (340–390 m a.s.l. in the NE part of Czechia). Flood countermeasures in a residential area above the study site created conditions conducive to accelerated erosion in the gullies; thus, the main aim of this study was to determine how human interventions changed the spatio-temporal dynamics of the gullies during a short period. Twenty two gullies (with a mean length 48.5 m) have developed on a 1-km-wide escarpment (with a mean slope 25°) composed of glaciogenic sediments of various sizes. Dendrogeomorphic techniques were applied on 23 exposed roots of Tilia cordata Mill. (a tree species that has never been used to detect root exposure). Microsections were prepared using a G.S.L.1 sledge microtome and analysed using the WinCELL Reg software to determine the timing of root exposure. Approximately 90% of the eroded sediments (1287.4 m 3 ) were transported across the railway onto the floodplain and caused damage to dwellings, while approximately 10% created bare accumulations at the gully floors. The most significant pulses of gully erosion occurred during the last 10 years (2007, 2009, 2010, and 2014). The maximum identified gully erosion occurred in 2014 (max. incision: 154 cm; maximum widening: 160 cm). In contrast, the development of the bank failures has been slowly progressing since the early 1990s, with a mean bank eroded area between 0.07 and 0.12 m 2 year −1 . The analysis of the precipitation characteristics (1963–2016) with the Mann-Kendal trend test revealed no significant trend. However, the last strong erosion event, in May of 2014, was triggered by an extraordinary rainstorm with an hourly intensity of 41.3 mm h −1 (maximum intensity of 2.8 mm min −1 ). Therefore, the recent increase in gully erosion is the consequence of extreme precipitation and human interventions that have been performed in the study site since 2007 (i.e., damming of the ditches and building of new culverts). The dendrogeomorphic research of exposed T. cordata roots significantly contributed to the identification of the gully erosion pulses and thus can be further applied in other localities. Highlights: We applied interdisciplinary approach to analyse gully erosion in NE Czechia. Exposed root network of T. cordata allowed determining of gully erosion rates. 0.7–1.5 m gully incision was identified during the erosion events in 2010 and 2014. Unreasonable human interventions influenced the spatial dynamics of gullies. Intense (40 mm h −1 ) and highly localized rainstorms triggered sudden gully erosion.