Epsilon Archive for Student Projects

Abstract

This study investigates the interactions between soil physical, chemical and biological parameters as well as the influence of climatic, environmental and spatial components on them in the context of dike stability along the Morava-Thaya river system in Central Europe. Climatic variability with more frequent droughts and extreme precipitation events in the future, induced through climate change, might affect flood protection systems through changes in soil structure, hydrology and biogeochemical processes. This study aims to identify dominant environmental gradients, site-specific variability and assess the potential implications for dike stability in the mentioned region.

In total, 20 dike sites, including 4 measurement points on the landside and waterside were taken into consideration together with management practices, exposition, distance to agriculture and to forest as well as location along the dam. Soil texture, bulk density, aggregate stability, organic matter fractions, nutrient availability, microbial biomass, enzyme activities, soil moisture, and temperature were analyzed together with climatic variables.

The results revealed a pronounced spatial heterogeneity along the dam. Coarse-textured sandy sites with lower moisture, reduced microbial biomass, weaker macroaggregate stability and lower organic carbon content could favor piping, seepage and internal erosion. On the other hand, finer-textured sites exhibited stronger aggregation, greater nutrient availability and increased microbial biomass. There, an increase in water retention capacities could occur, but also an increase in vulnerability to shrink-swell dynamics, desiccation cracking and preferential flow formation during drought periods.

Organic carbon, microbial biomass, nutrient availability and macroaggregate stability are indicators of biologically mediated aggregation processes, which can contribute to structural cohesion of dike soils. Additionally, climatic gradients could exert an influence on microbial functioning and aggregation processes along the dike system, where warmer conditions can lead to the promotion of nutrient turnover and enhanced biological activity, while wetter and colder conditions were associated with increased microaggregation and phosphatase activity.

In the PCA analysis, a distinct hydro-biogeochemical gradient structured the dataset where coarse-textured, enzyme-active soils were separated from nutrient-rich and microbially enriched soils. The hydrological position and management practices considered revealed an increase in compaction and structural variability, especially on the waterside and grazed sections.

Overall, dike stability appears to be controlled by interacting with hydro-biogeochemical processes, not isolated geotechnical parameters alone. The importance of integrated physicochemical, biological, climatic and soil structural indicators and hydrological monitoring has been highlighted for the assessment of flood dike stability and establishing an effective flood protection management system (J.-M. Zhang et al., 2021). Spatial heterogeneity may lead to different vulnerability pathways for the dike system under climate change scenarios. Therefore, an emphasis on site-specific and process-based approaches to long-term dike resilience assessment is advised.