Investigations on the runoff generation at the profile and plot scales, Swiss Emmental

Abstract

Abstract:This article describes an investigation on runoff generation at different scales in the forested catchment of the Sperbelgraben in the Emmental region (Swiss Prealps) where studies in the field of forest hydrology have a history of 100 years. It focuses on the analysis of soil profiles and the subsequent sprinkling experiments above them (1 m 2 ), as well as on surface runoff measurements on larger plots (50 to 110 m 2 ). In the Sperbelgraben investigation area, two very distinct runoff reactions could be observed. On the one hand, very high production of saturation overland flow was registered on wet areas of gleyic soils, with runoff coefficients between 0Ð39 and 0Ð94 for profile irrigation. On the other hand, almost no surface runoff was measured on Cambisols, with the exception at some sites of a hydrophobic reaction detected at the beginning of storms after dry periods (coefficients for profile irrigation: 0Ð01-0Ð16). This pattern was observed during 1 m 2 soil plot irrigation and on surface runoff plots. Apart from a less distinctive signal of the water-repellent litter layer on the larger surface runoff plots, the dominant hydrological processes at the two scales are the same. The determined runoff reaction at the two scales corresponds well with information from a forest site type map describing soil and vegetation characteristics and used as a substitute for a soil map in this study. Theoretical considerations describing forest influence on flood discharge are discussed and evaluated to be in good agreement with observations. These findings are a sound foundation for application in hydrological catchment modelling.

Dynamic runoff connectivity of overland flow on steep forested hillslopes: Scale effects and runoff transfer

“…Flow within and across fallen leaves and branches may also promote overland flow because we installed aluminum flashing 1 to 3 cm under soil surface. This near-surface phenomenon is called quasioverland flow [Burch et al, 1989;Badoux et al, 2006] or biomat flow [Sidle et al, 2007]. Stemflow likely contributes only a trivial amount to overland flow because it typically comprises just 1 to 10% of precipitation [Levia and Frost, 2003].…”

“…Although overland flow occurred both from Japanese cypress and deciduous forest hillslopes, greater opportunities for infiltration create more discontinuous overland flow on deciduous forest slopes and Japanese cypress slopes with dense understory vegetation. Therefore, flow occurring near the organic horizon -mineral soil interface may infiltrate deeper in the soil and may not contribute to catchment storm runoff [Badoux et al, 2006;Sidle et al, 2007]. Litter on the forest floor also provides a site for temporary water storage and infiltration [Putuhena and Cordey, 1996].…”

Significance of tree roots for preferential infiltration in stagnic soils

“…For example, Cognard-Plancq et al (2001) claimed that forest-covered soils can store more water than soils without trees. Water storage depends not only on the percentage of forested area, but also on the forest site in a catchment area, as different sites influence infiltration capacities differently (Badoux et al, 2006). Hegg et al (2004) showed that water storage capacities vary depending on the type of forest site.…”

Shallow Interflow

“…Informationen zur Genese des Zwischenabflusses zu erhalten (z.B. Scherrer 1997, Weiler und Flühler 2004, Badoux et al 2006, Kienzler 2007, Laule 2007, Tromp-van Meerveld und Weiler 2008 und um diese Informationen mit entsprechenden Algorithmen in hydrologische Modelle zu integrieren. Allen diesen Arbeiten ist das Problem der unklaren Übertragbarkeit der auf der Plot-Skala gewonnenen Daten auf kleinere Maßstabsebenen gemeinsam (Germann und Weingartner 2002, Cerdan et al 2004).…”