Abstract
This study investigates the effects of pumice excavation on runoff formation and soil erosion processes in a forested catchment in SW-Germany. The underlying questions are, if (a) backfilled soils have different properties concerning runoff generation and erodibility and if (b) clear-cutting prior to excavation triggers runoff and erosion. Four adjacent sub-areas were observed, which represented different pre- and post-excavation-stages. The basis of the investigation was a comprehensive field sampling that delivered the data for physical erosion modeling using the Water Erosion Prediction Project (WEPP). Modeling took place for standardized conditions (uniform slope geometry and/or uniform land management) and for actual slope geometry and land management. The results show that backfilled soils exhibited 53% increase of annual runoff and 70% increase of annual soil loss under standardized conditions. Storm runoff was increased by 6%, while storm soil loss was reduced by 9%. Land management changes also triggered shifts in annual runoff and soil erosion: Clear-cut (+1.796% runoff, +4.205% soil loss) and bare (+5.958% runoff, +21.055% soil loss) surfaces showed the most distinct changes when compared to undisturbed forest. While reforestation largely diminished post-excavation runoff and soil erosion, the standardized results statistically prove that soil erodibility and runoff generation remain increased after backfilling.
Highlights
While reforestation largely diminished post-excavation runoff and soil erosion, the standardized results statistically prove that soil erodibility and runoff generation remain increased after backfilling
This study is concerned with runoff generation and soil erosion processes in the aftermath of pumice excavation at forested sites in southwestern Germany
It is difficult to classify disturbed soils in this study according to common soil classifications like [47]: As they do not meet the requirements of an anthropogenic altered Technosol, some kind of altered Andosol, most likely a “Relocatic Andosol” has to be assumed
Summary
This study is concerned with runoff generation and soil erosion processes in the aftermath of pumice excavation at forested sites in southwestern Germany. The last major eruption of the Laacher. See volcano (12,916 yr B.P.) in northern Rhineland-Palatine covered surrounding areas with Laacher. Pumice ashes and lapilli were wind-deposited in a heterogeneous pattern in the northeastern direction. While thin ash depositions with a thickness of only a few millimeters were carried even to southern Sweden [3], the majority of LST was deposited in a narrow sector, not exceeding 40 km length in east/northeast direction [2]. LST functions as the base condition for an Andosol-pedogenesis. Especially LST-Andosols, usually exhibit low dry bulk densities and high pore volumes, which are caused by coarse pumice particles [6,7,8]
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