Digital Modeling of Lateral Water and Caesium-137 Flows at the Microlandscape Level in Semihydromorphic Soils of Bryansk Oblast

Preferential vertical water flows play a significant role in water movement within the soil profile; while lateral flows attract less attention from researchers. This paper proposes a method that uses ¹³⁷Cs of Chernobyl origin as a marker to examine lateral moisture flows at the microlandscape level. GIS modeling of lateral moisture transfer was performed on the basis of hydrological microrelief parameters derived from a digital elevation model (DEM) produced at a scale of 1 : 200 with contour intervals of 20 cm. Such parameters as catchment area, overland flow distance, ephemeral trickle network (constructed using the Horton–Strahler stream ordering), and topographic wetness index (TWI) qualitatively describe soil wetting intensity and lateral flows at the microlandscape level. The concept of “preferential lateral flows” has been introduced by analogy with “preferential vertical moisture flows.” Due to the spatial features of the nano- and microrelief structure, lateral transfer forms ephemeral patterns with different moisture regimes: “finger-shaped,” filamentous, etc. It was found that lateral ¹³⁷Cs migration slightly depends on DEM derivatives.