The mass distribution of coarse particulate organic matter exported from an alpine headwater stream

Abstract

Abstract. Coarse particulate organic matter (CPOM) particles span sizes from 1 mm, with masses less than 1 mg, to large logs and whole trees, which may have masses of several hundred kilograms. Different size and mass classes play different roles in stream environments, from being the prime source of energy in stream ecosystems to macroscopically determining channel morphology and local hydraulics. We show that a single scaling exponent can describe the mass distribution of CPOM transported in the Erlenbach, a steep mountain stream in the Swiss Prealps. This exponent takes an average value of −1.8, is independent of discharge and valid for particle masses spanning almost seven orders of magnitude. Together with a rating curve of CPOM transport rates with discharge, we discuss the importance of the scaling exponent for measuring strategies and natural hazard mitigation. Similar to CPOM, the mass distribution of in-stream large woody debris can likewise be described by power law scaling distributions, with exponents varying between −1.8 and −2.0, if all in-stream material is considered, and between −1.4 and −1.8 for material locked in log jams. We expect that scaling exponents are determined by stream type, vegetation, climate, substrate properties, and the connectivity between channels and hillslopes. However, none of the descriptor variables tested here, including drainage area, channel bed slope and forested area, show a strong control on exponent value. The number of streams studied in this paper is too small to make final conclusions.

Wood export varies among decadal, annual, seasonal, and daily scale hydrologic regimes in a large, Mediterranean climate, mountain river watershed

“…The − scaling exponent mean was 1.84, with a 119 range 1.41-2.26, using 28 samples. Wood data from the Ain River (MacVicar and Piégay, 120 2012) yielded a similar − value of 1.8, which may help to independently support the use 121 of a scaling exponent to predict " frequency (Turowski et al, 2013 The heavily forested watershed has a disturbance legacy as one of the epicenters 166 of the California gold mining era in the mid-to late 1800s when hydraulic mining 167 operations and other extraction methods dramatically altered stream corridor 168 morphology, riparian continuity, and aquatic ecology (Gilbert, 1917;James, 2005 …”

“…Additional regression analyses excluded 516 days where wood pieces and volume equaled zero, which allowed for exploration of 517 power functions (Eq. (3); Turowski et al, 2013). The most robust outcome was found 518 when "# was regressed against maximum daily GYB , an analysis that included all 519 non-zero days of data (Table 2).…”

“…Use of a stilling basin and bedload traps allowed Turowski et al (2013) to collect 111 wood data across three orders of magnitude in mass, 1 g to 3 kg (i.e., particulate to large 112 wood sizes), exporting from a small headwater catchment in the Swiss Alps. They 113 developed a power relation between decreasing number of wood pieces and increasing 114 particle mass, reported in the form of:…”

“…A frequency analysis was performed 504 following Eq. (2) (Turowski et al, 2013) to test for similarities in − scaling exponent 505 values. Wood piece lengths and volume for this test were sorted on the basis of the 506 same hydrological mechanisms described above as well as by discharge, and then 507 values were log base-2 transformed, binned by 0.5 increments, plotted, and finally, 508 power functions were calculated via trendline analysis to derive scaling exponent values.…”

KULTURisk regional risk assessment methodology for water-related natural hazards – Part 2: Application to the Zurich case study

“…The river valley is also cultivated with crops and pastures. The upstream part of the river consists of several small torrential rivers, characterized by the intense transport of sediments (Rickenmann et al, 2012) and driftwood (Turowski et al, 2013). The intense transport of sediment is particularly evident when the brown waters of the Sihl (Fig.…”