Runoff production processes in small alpine catchments within the unconsolidated Pleistocene sediments of the Lainbach area (Upper Bavaria)

Abstract

Abstract:In the Lainbach catchment, unconsolidated Pleistocene moraine sediments are widely distributed. Because of the great natural risk of floods, together with extreme loads of sediments, investigations of runoff production processes have been conducted in this area. At hillslope scale three test sites with different states of soil development and vegetation cover were instrumented with V-shaped weirs, precipitation gauges and measurement devices for electrical conductivity (EC) of discharge water. The EC has been used as a geochemical tracer for hydrograph separation, since the statistical relationship between content of dissolved Ca 2C , Mg 2C cations and EC is highly significant for different stages of runoff. This method allows hydrograph separation at high temporal resolution for both the rising and falling limb of the hydrograph. The following results of the investigations can be resumed. If relief conditions are similar, the effectiveness of runoff production decreases with an increasing density of vegetation cover. The runoff delivery ratio decreases as well as the peaks of runoff. In contrast, concentration times of hillslope catchments are equal, even if vegetation cover is of great density and soils are well developed. As a reason for the short reaction times, different runoff production processes have been detected. On bare ground, infiltration excess overland flow intensified by surface sealing processes is the main source for quick runoff. On hillslopes well covered by vegetation, translatory flow processes indicated by soil water with high solute contents force a rapid runoff reaction only a few minutes after rainfall has begun. It is to be assumed that translatory flow is a runoff production process typical for hillslopes covered by vegetation in a steep alpine relief. By means of the areal distribution of the topographic index, concentration of runoff production on a small part of the catchment has been demonstrated for hillslopes densely covered by vegetation. The investigations have shown that there is a lack of studies on runoff production processes in steep alpine relief, as well as a deficit of methods to quantify hydraulic properties of coarse-grained soils with a wide grain size distribution.

Effects of Stock Use and Backpackers on Water Quality in Wilderness in Sequoia and Kings Canyon National Parks, USA

“…This is supported by data from a 1999 synoptic survey of high-elevation lakes and streams in national parks in the western U.S. (including the WLS lakes sampled in SEKI), which indicated no statistically significant differences in the chemistry of lakes and streams (Clow et al 2002;2003). This is not expected to be the case for all environments, but appears to be true for the high-elevation water bodies that were sampled in the 1999 study, which the SEKI WLS lakes were part of.…”

“…Two of the intensive-monitoring sites were installed at Sandy Meadow; one set of the aforementioned equipment was installed above the meadow (5) and another set was installed below the meadow (6). In addition, automated water samplers were installed at the two Sandy Meadow sites to collect water samples during storm events, when most transport of suspended sediment, nutrient, and fecal bacteria typically occurs (Peters 1994;Tsihrintzis and Hamid 1997;Wetzel 2003;Davies-Colley et al 2008;McKergow and Davies-Colley 2010). The autosamplers were programmed to trigger during storms by a rise (and subsequent fall) in stage over a 10-min period exceeding specified criteria (e.g., 0.02 ft).…”

Determination of hydrological roughness by means of close range remote sensing

“…Being object to many research projects in several geoscientific disciplines (Banasik and Bley, 1994;Bunza et al, 2004;Grottenthaler and Laatsch, 1973;de Jong, 1995;Schmidt, 1994;Wetzel, 2003) the Lainbach valley in the Northern Limestone Alps (47 • 40 35 N and 11 • 27 35 E) was chosen for the field experiments. Altitudes in the 18.4 km 2 catchment range from 1801 m at the Benediktenwand to around 700 m at the outlet of the river Lainbach close to the city of Benediktbeuern.…”

“…A C-band radar evaluation for determining surface roughness was carried out by Rahman et al (2008) using satellite data from Envisat and validating them with pin meter measurements. Zheng et al (2012) published a study closely related to our work as they compared soil surface roughness with a hydraulic roughness coefficient. They derived functions to relate the Manning's n to the measured surface roughness and could thus achieve good coefficients of determination (R 2 = 0.89) for different slope gradients on loessic soils.…”

“…They derived functions to relate the Manning's n to the measured surface roughness and could thus achieve good coefficients of determination (R 2 = 0.89) for different slope gradients on loessic soils. Nonetheless, the range of different grain sizes and thus surface roughness is restricted to one soil type and the measurement was carried out using a pin meter (Zheng et al, 2012). The latter is a useful tool for random roughness measurements and has also been applied in older studies for determining surface roughness values.…”