Modeling Runoff-Formation and Soil Erosion after Pumice Excavation at Forested Andosol-Sites in SW-Germany Using WEPP

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.

Penetration Resistance of Laacher See-tephra Andosols—Evaluating Rooting Conditions of Undisturbed and Excavated Forest Soils in SW-Germany

“…Soil data was sampled in the fall of 2018 prior to this study for FOR, CUT, SUC and REF, using a variety of parameters in a soil erosion study [48]. This dataset consists of 485 individual soil samples, taken at 117 sampling points (3 catenae per area, each consisting of 10 sampling points; 3 sampling points were excluded because of corrupted data).…”

“…On undisturbed sites (FOR and CUT), a horizon-wise sampling took place, while five depth-slices of 0.2 m were sampled on disturbed/backfilled sites, covering the upper first meter of the soil, as they did not have pedogenetic horizons anymore. This dataset is expanded by soil moisture measurements, which were conducted simultaneously but were not included in [48]. On CUT EX, an additional 205 samples were taken in early summer of 2019, consisting of 51 individual sampling points and again five depth classes covering 0.2 meters each.…”

“…On CUT EX, an additional 205 samples were taken in early summer of 2019, consisting of 51 individual sampling points and again five depth classes covering 0.2 meters each. These samples were also not included in [48]. Parameters used and discussed in this study are soil texture, soil moisture (SM) and soil organic matter (SOM).…”

“…Overall, five different sub-areas were observed in this study ( Figure 2). Location of the study area (after [37,48]).…”

Soil Erosion and Land Degradation

“…The effect of land management on Andosols is addressed by Zemke et al [3], who applied the physically-based soil erosion model WEPP (Water Erosion Prediction Project) together with comprehensive field sampling in a forested catchment in Germany. The focus of this study is on the role of clear-cutting and reforestation on backfilled soils after pumice excavation for runoff generation and soil erodibility.…”