Effects of lithology and land use on storm run‐off in east luxembourg

Abstract

For a large part of the year, the forested catchments in the Keuper formation of east Luxembourg produce more direct run-off on a storm basis than paired cultivated catchments. The occurrence of shrinkage cracks, their pronounced opening and closing, and the occurrence of natural pipes in the forested environment play a major role in explaining this phenomenon. The effect of land use on storm run-off is studied in relation to that found for lithology in the same area.KEY WORDS Direct run-off Land use Shrinkage cracks Natural pipes OBJECTIVESThe objectives of this study were (1) to establish the relative quantitative effects of lithology and land use on storm run-off for small catchments in east Luxembourg, and (2) to relate these effects to dynamic hydrological processes observed in the field. EXPERIMENTAL DESIGNA network for measuring rainfall and discharge was designed and established in April 1984 within the Keuper marls and Luxembourg sandstone formation. Precipitation was measured at four sites with Siap tipping bucket recorders mounted 60 cm above ground level, and discharge was measured at six sites using 90" V-notch weirs (Thomson weirs), equipped with either Seba or Leopold and Stevens stage recorders (Figure 1). The catchments were visited at least monthly for 18 months. STUDY AREAForested soils in the Keuper marls are characterized by many large biopores and natural pipes in the surface soil caused by the combined action of root decay and the activity of earthworms, voles and moles, and by a clayey B-horizon at approximately 30 cm, causing a rapid decrease in vertical profile permeability. The Keuper soils under cultivation or pasture differ from those under forest in being truncated to the lower B-or C-horizons. The weathering product of the Luxembourg sandstone, in contrast, is a permeable loamy sand. Information on lithostratigraphy and land use for the studied catchments are presented in Table I and Figure 2. A full description of the fieldwork area is presented in Hendriks (1990). HYDROMORPHOMETRIC DATAAs run-off data are highly correlated with catchment physiography (NERC, 1975), catchment values for a number of hydromorphometricai variables were determined.

A review of two strongly contrasting geomorphological systems within the context of scale

“…Critical conditions affecting runoff generation at the finest scales (runoff test site) are rainfall intensity, antecedent moisture content, soil depth, the presence of semi-permanent pipe systems and soil biological activity via the presence of earthworms (Lumbricus terrestris) and moles (Talpa europea) (Cammeraat, 1992;Calver and Cammeraat, 1993;Hendriks, 1993). Runoff is mainly produced in partial areas (approximately 50 ð 50 m), which form very shallow depressions with very dynamic hydrological behaviour (Bonell et al, 1984).…”

The applicability of a parsimonious model for local and regional prediction of runoff

“…These findings show that, notwithstanding an overall satisfactory ability to reproduce the entire hydrographs for a large range of basin sizes and geological substrates, the model's structure and assumptions are not able, in certain conditions, to account fully for the complexity of the physical processes involved in flood generation (Bonell et al, 1984;Hendricks, 1993;Pfister et al, 2000b). Furthermore, the conceptualization of the dependence of basin response during an event on the antecedent hydrological and meteorological characteristics is still a crucial point.…”

Biological control of pedological and hydro-geomorphological processes in a deciduous forest ecosystem

“…50% clay) and is classified as an Aquic Distric Eutrochrept following the USDA classification (Broek 1989) or a Luvic or Vertic Planosol (FAO 2006). The top soils are generally very porous due to high biological activity (Hendriks 1993). The soil has a very characteristic hydrological behaviour.…”