sediment output and effective discharge in two small high ... morche 2006.pdf · sediment output...

2006) 131–145www.elsevier.com/locate/geomorph

Geomorphology 80 (

Sediment output and effective discharge in two small high mountaincatchments in the Bavarian Alps, Germany

Karl-Heinz Schmidt ⁎, David Morche

Physical Geography, Martin-Luther-University Halle-Wittenberg, D-06099 Halle, Germany

Accepted 27 September 2005Available online 11 April 2006

Abstract

Sediment output (solid and dissolved load) from two small Alpine rivers (Partnach and Lahnenwiesgraben in the Bavarian Alps)was measured during three summer field seasons from 2001–2003. There is high spatial variability of sediment output between thecatchments and a high temporal variability between observation periods. Sediment transport in the Partnach river (Reintal) isdominated by solute load, whereas the Lahnenwiesgraben river transports a much greater proportion of solid load. This differencecan mainly be explained by the different lithologies of the systems. The Reintal catchment is dominated by massive Triassiclimestone. In the Lahnenwiesgraben catchment, in addition to limestones, unconsolidated rocks, marls and mudstone layers aresignificant. Furthermore, large rockslide dams in the Partnach valley isolate large parts of the Reintal catchment from solid loadoutput.

The components of fluvial sediment transport were, where possible, calculated by using flow duration curves and rating curvetechniques. In the Lahnenwiesgraben event specific rating curves were used to determine suspended load. On the broad database of55 measured flood events in the Lahnenwiesgraben a good correlation (rPearson=0.9) between event peak discharge and suspendedload of the event was established.

Effective discharge was calculated for the different types of sediment load (solid and dissolved) and total load. In the Reintaleffective discharge for total load is found in low flow classes close to mean discharge, because sediment output is dominated bydissolved load, which has its maximum efficiency at low and moderate discharges. In the Lahnenwiesgraben most work is done bydischarges much higher than mean discharge during extreme individual flood events.© 2006 Elsevier B.V. All rights reserved.

Keywords: Sediment transport; Dissolved load; Suspended load; Bed load; Rating curve techniques; Effective discharge; Event peak discharge;Bavarian Alps

1. Introduction

The research project “Sediment Transfer in AlpineDrainage Systems—Mobility and Functional Connec-

⁎ Corresponding author. Tel.: +49 345 5526042; fax: +49 3455527175.

E-mail addresses: [email protected](K.-H. Schmidt), [email protected] (D. Morche).

0169-555X/$ - see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.geomorph.2005.09.013

tions” deals with questions of fluvial sediment transportand the coupling or decoupling of slope and fluvialtransport processes. It is a part of a joint project, inwhich, since 1998, several geoscientific universitydepartments have investigated the relationships betweengeomorphic transfer processes (mass movements, ava-lanches, aquatic slope processes, river transport, storagesystems) in Alpine sediment cascades (SEDAG=Sedi-ment Cascades in Alpine Geosystems). First results of

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http://dx.doi.org/10.1016/j.geomorph.2005.09.013

132 K.-H. Schmidt, D. Morche / Geomorphology 80 (2006) 131–145

this joint project have been published in Schmidt andVetter (2002). Since 2004 our research project hasparticipated in the SEDIFLUX network of the EuropeanScience Foundation (ESF) on sediment fluxes in coldenvironments, where it specifically deals with source tosink fluxes in cold mountain environments.

Fluvial sediment transport is an important element ofhigh mountain sediment cascades. Especially informa-tion on fluvial sediment output from the systems isnecessary for the calculation of sediment budgets. Asfluvial processes are highly variable in mountainenvironments, longer time periods are needed to createcomplete and reliable budgets, especially when they aremeant to include the mass balance input of rock falls,avalanches, side valleys, slope wash and debris flows.Numerous studies have dealt with sediment transportand sediment-budgets in small catchments in the Alps(e.g. Becht, 1989; Schmidt et al., 1992; Ergenzinger and

Fig. 1. Location of the two study areas. Gauβ-Krüger coordinates at the mProjection).

Schmidt, 1994; Wetzel, 1994; Rickenmann, 1997;Schrott et al., 2002).

Though many studies have tried to establish budgetsof the sequence of processes many unknowns remain inthe calculations, and the numerical integration of thelinks of the sediment cascade fail. Most of the previousstudies have concentrated on one or two compartmentsof the process sequence (Keller and Moser, 2002;Unbenannt, 2002; Haas et al., 2004) with the inclusionof aspects of sediment sources and sinks (Schrott et al.,2003; Morche and Schmidt, 2005). Information isfragmentary and some considerable problems remainto be solved. The difficulties of constructing a completesediment budget including all compartments of thesediment cascade are highlighted when the compara-tively uncomplicated problem of fluvial sediment outputfrom a system is considered, where a number of difficultquestions have to be addressed such as suspended

ap margins are based on the 3° Bessel ellipsoid (Transverse Mercator

Table 1Selected physiographic and topographic features of the study sites

Study area Lahnenwiesgraben Reintal (withoutZugspitzplatt region)

Name of the river Lahnenwiesgraben PartnachCatchment area

(km2)16.62 17.33

Altitudinal range(m a.s.l.)

707 to 1980 1047 to 2742

Mean slopeangle (degree)

28.8 41.2

Precipitation(mm)

Approx. 1600 to 2000 Approx. 2000

Upper forestlimit (m a.s.l.)

Approx. 1700 Approx. 1700

Dominantlithology

Limestone (Hauptdolomit,Plattenkalk), mudstones(Kössener Schichten),Aptychenschichten

Limestone(Wettersteinkalk)

133K.-H. Schmidt, D. Morche / Geomorphology 80 (2006) 131–145

sediment and bed load measurement and related ratingcurves and other extrapolation techniques (Walling,1977; Schmidt, 1984; Knighton, 1998; Bunte, 1999).The aim of this paper is to illustrate and discuss methodsfor the calculation of total sediment export from amountain river system and thus to provide a reliablebasis for the assessment of output in the construction ofsediment budgets.

Another point to be highlighted is the determinationof effective discharge, which will yield importantinformation on the significance of different dischargemagnitudes and frequencies for sediment output. Greatdissimilarities in the attributes of effective dischargefor the different types of sediment load can beexpected because of the strong diversity of the basinswith respect to lithology and the states of buffering andconnectivity.

2. Study sites

The research areas are located in the Bavarian Alpsabout 80km south of Munich near Garmisch-Parten-kirchen. The Reintal catchment is drained by thePartnach river and the Lahnenwiesgraben catchmentby the eponymous Lahnenwiesgraben river. Bothrivers are tributaries of the Loisach river (Fig. 1).The upper parts of both catchments belong to a nivalclimatic regime with thick snow covers in winter andfrequent avalanches and meltwater-induced high dis-charges in spring. The most severe floods are causedby heavy summer rainfall. The main topographic andphysiographic attributes of the study sites are listed inTable 1.

2.1. The Reintal valley

The Reintal valley is a model example of a U-shapedvalley (Fig. 2), formed by a local glacier during the last(Würm) glaciation. Hirtlreiter (1992) mapped theterminal moraines of the late glacial stages on theslopes of the Reintal and on the valley floor. Two highmagnitude rockslide events created rock-dammed lakes(Vordere Blaue Gumpe, Hintere Blaue Gumpe) in theReintal valley (Figs. 2 and 3). The smaller rockslidedamming the Vordere Blaue Gumpe occurred about 200years ago (Morche et al., in press), the larger onedamming the Hintere Blaue Gumpe occurred between1400 and 1600AD (Schrott et al., 2002). Fluvialsediment transport is disrupted by the rockslide lakesand thick deposits have been accumulated behind thebarriers (Schrott et al., 2003). Thus the Reintal is anexcellent example of a disconnected sediment cascade at

a catchment scale. For the detailed distribution ofsediment storage types and sources and sinks in theReintal valley see Schrott et al. (2002, 2003) andMorche and Schmidt (2005).

Fluvial processes transport sediment particles to thesinks within the system (landslide dammed lakes,alluvial plains and deltas behind the barriers, terraces,channel bars and the river bed), and only a small part ofthe eroded material is transported to the outlet of thecatchment. Sediment pathways and the connectivity ofsediment sources and sinks in the sediment cascade ofthe Reintal were analyzed by Morche and Schmidt(2005), who used particle size and particle shapeproperties for identification.

A great part of the discharge (base flow) in thePartnach is supplied by a karst spring (Partnachur-sprung) (see Fig. 3), which drains the karst plateau(Zugspitzplatt) near the highest mountain of theWettersteingebirge (Zugspitze 2962m) and adds asubsurface drainage area of about 11km2 to the Reintalcatchment (see Fig. 10a). This additional input of runoffand solutes must be considered when comparingdischarge and dissolved load output from the Reintaland the Lahnenwiesgraben.

2.2. Lahnenwiesgraben

The Lahnenwiesgraben catchment was allochtho-nously glaciated during the Würm glaciation andlarge areas are covered by unconsolidated glacialsediments derived from outside the catchment, whichremain as potentially active sediment sources. TheLahnenwiesgraben is underlain by mixed lithologies

Fig. 2. Reintal, a formerly glaciated valley, very coarse rockslide debris in the foreground damming the Hintere Blaue Gumpe and the snow coveredZugspitzplatt (altitudinal range about 2000–2500m) in the background.


including impermeable marls and mudstones (Table1). These attributes make the slopes in the Lahnen-wiesgraben highly susceptible to gravitational slopedynamics such as slow mass movements and debrisflows. Direct runoff is the major constituent of totalflow, and the system has short lag times betweenprecipitation input and flood flows. Channel disconti-nuities in the Lahnenwiesgraben are only caused byman-made river training structures with bed-loadretaining check dams. Thus at the times when thecheck dams are filled by sediments, which was thecase during our observation periods, the Lahnenwies-graben has the general character of a fully connectedsystem.

Fig. 3. Longitudinal profile of the Partnach r

3. Methods

3.1. Measuring stations

This paper is based on the evaluation of data fromthree field campaigns in the summers 2001 to 2003.Measuring stations will be in operation until the end of the2005 season. The measurements of the first 3 years arenot sufficient to obtain reliable mean values of sedimentoutput of the basins for all discharge classes, they willonly yield preliminary results, which will, however, bevery helpful for the understanding of the main aspects ofthe temporal and spatial characteristics of total sedimentoutput and for the calculation of effective discharge.

iver (modified after Unbenannt, 2002).


Moreover, in our observation period we experienced thehighest discharge ever recorded at the official Lahnen-wiesgraben gage in almost 20 years, which is a greatadvantage in the calculation of both sediment outputduring extreme events and effective discharge.

Recording stations were installed at each of thecatchment outlets. They log water level and electricalconductivity every 15min, and, in the Lahnenwiesgra-ben, turbidity as an additional parameter (Hachtransmittance sensor, backwash turbidimeter model19800). The stations are equipped with automaticwater samplers (Sigma, model 900) for regular andevent related sampling. Parameters analyzed in thesamples are suspended sediment concentration andgrain-size distribution as well as the solute concentrationand ion composition of the dissolved material. Atselected water level stages discharge was measuredusing a current meter (Ott: model C2) and bed load wascollected with portable Helley–Smith samplers (3×3 in.in the Reintal, 6×6 in. in the Lahnenwiesgraben).

3.2. Calculation of solid and dissolved loads

Acommonway to calculate annual load and the load ofindividual flow classes is by using the flow duration curveand rating curves for the individual sediment transportcomponents. This was, however, not possible for allcomponents on the same level of reliability, which has tobe considered in the subsequent evaluation of the results.Campbell and Bauder (1940) developed a simple butreliable and often used method for calculating suspended

Fig. 4. Rating curves of discharge versus SSC (Partnach

sediment transport, the so-called rating curve technique,which allows the extrapolation of field measurementswith the help of regression equations. In small moun-tainous catchments, however, the general correlationbetween suspended sediment concentration (SSC) anddischarge is generally poor. In the buffered system of theReintal, on the other hand, the calculation of SSC waspossible with a polynomial rating curve for dischargesabove 4m3 s− 1. For discharges below 4m3 s− 1 anexponential function with a lower correlation coefficienthad to be used (Fig. 4). Nonetheless the scatter in therelations is considerable and individual estimates areliable to large errors. In the Lahnenwiesgraben thecalculation of SSC had to be performed with eventspecific rating curves, which for some events gavereliable results (cf. Fig. 9). In most events they had to beseparated for the limbs of the hydrographs (cf. Unbe-nannt, 2002). Calculated in this way the differentregression functions show strong relations betweendischarge and SSC. Fig. 5 presents an example of aclockwise hysteresis of this relation with highly signif-icant correlation coefficients.

A great variety of bed-load transport formulae havebeen proposed for estimating bed-load transport (forreviews and compilations see Gomez and Church, 1989;Zanke, 1982). Recently, Martin (2003) evaluated themost important formulae with field data from rivers inBritish Columbia. She came to the conclusion that noneof them should really be recommended. In a paperproposing practical methods for estimating sedimenttransport Wilcock (2001, p. 1395) stated that formulae

river), based on samples taken in 2001 and 2002.

Fig. 5. Clockwise hysteresis relation between discharge and SSC and event specific rating curves for the May 31st and June 1st 2003 flood event(Lahnenwiesgraben).


are “notoriously inaccurate”. This especially applies tocoarse material torrents (Ergenzinger and Schmidt,1994). Similarly in the Reintal and Lahnenwiesgrabenthe attempts to apply bed-load transport formulae werenot successful.

Thus, in constructing sediment budgets for the twosmall rivers empirical methods were thought to have abetter potential for application and to yield more reliableestimates. Therefore for calculating bed-load transport

Fig. 6. Bedload rating curves of the two rivers. In the Partnach river no beencircled value in the Lahnenwiesgraben data shows a measured bed load valafter dredging activities upstream behind a check dam.

rate data from Helley–Smith samples and bed-loadrating curves were used. The rating curve correlation forbed-load computation for the Lahnenwiesgraben river isstronger (rPearson=0.78) than that for the Partnach river(rPearson=0.53). This can be explained by the generallylow transport rate and variability in the disconnectedsystem of the Partnach. But both of the regressions arehighly significant (Fig. 6). Yet many attempts havedemonstrated that extrapolations from Helley–Smith

d load material was transported at discharges below 2.4m3 s−1. Theue at a very low discharge. The bed load sample was taken a short-time

Fig. 7. Relation between electrical conductivity versus concentration of total dissolved solids in both rivers, based on measurements from 2001 and2002.


sampling programmes are only best estimates of actualbedload transport (see also the review by Bunte, 1999).

According to Schmidt (1984) there is a strongcorrelation between the concentration of total dissolvedsolids (TDS) and electrical conductivity (EC). This typeof correlation is also evident for the measurement valuesin the Reintal and the Lahnenwiesgraben (Fig. 7). Thevariation in electrical conductivity explains about 50%of the variation of TDS. As Unbenannt (2002) pointedout, about 98% of the cation mass are Ca2+ and Mg2+.This is controlled by the dominantly carbonaticchemical composition of the bedrock in the catchments(Miller, 1961). To get the whole TDS the equivalentweight of the CO3

− anion is added to the sum of thecation weight.

4. Results

4.1. Hydrographs

The hydrographs of the two Alpine rivers differconsiderably between the three observation periods(Fig. 8) with respect to peak, minimum and meandischarges (Table 2). Interruptions of the hydrographsare caused by malfunction of the data loggers or waterlevel sensors. Therefore there are different durations ofthe observation periods (Table 2).

Runoff is highly variable in the Lahnenwiesgraben; itreacts rapidly and sensitively to rainfall input. The floodhydrographs show short lag times and very steep rising

and falling limbs. In the Lahnenwiesgraben 55 floodevents were registered. The maximum discharge was26.13m3 s−1 during the May 31st and June 1st event in2003 (Fig. 9). Though the observation period for thispaper comprises only three summer seasons, the wholespan of discharge values measured at the Burgrain gageduring the 17-year long all season operation wasincluded during our field measurements.

The Partnach is a buffered system. Buffering iscaused by karst hydrology (Wetzel, 2004) and thestorage systems behind the landslide dammed lakes.Runoff peaks are less steep with longer base times.Discharge variability is much lower in the Reintal thanin the Lahnenwiesgraben. The ratio between maxi-mum and minimum discharge is about 22 in theReintal and about 2500 in the Lahnenwiesgraben. Thedifferent discharge characteristics of the catchmentshave important consequences for sediment transportdynamics. They make the two catchments interestingnatural experimental sites for comparing sedimenttransport attributes in coupled and uncoupled systemsas well as in buffered and non-buffered fluvialsystems.

4.2. Sediment output

Sediment output from the basins was calculated forthe individual measuring periods, using the ratingcurves and other methods described in the previoussection. It was not possible to compute annual load,

Fig. 8. Hydrographs of the observation periods 2001 (a), 2002 (b) and 2003 (c). The interruptions of the hydrographs were caused by data logger orwater level sensor failure.


Table 2Main discharge characteristics of the Partnach river (mean discharge of all three observation periods about 2.5m3 s−1) and the Lahnenwiesgrabenriver (mean discharge of all three observation periods about 0.5m3 s−1)

River Year/duration ofobservation period

Mean discharge(m3 s−1)

Peak discharge(m3 s−1)

Minimum discharge(m3 s−1)

Specific discharge(ls−1 km−2)

Partnach (Reintal plusZugspitzplatt region)

2001 137 days 2.99 5.56 2.15 106.332002 158 days 3.06 11.40 1.76 108.822003 108 days 1.05 2.88 0.52 37.33

Lahnenwies-graben 2001 137 days 0.67 10.38 0.09 40.312002 207 days 0.61 25.10 0.14 36.702003 208 days 0.29 26.13 0.01 17.34


because field measurement were only carried out duringthe summer season, which geomorphologically is themost active part of the year with respect to sedimenttransport. Moreover, the field observation periods haddifferent lengths (Table 2). So sediment load is ex-pressed as mean daily sediment yield (kg day− 1 km− 2)for the two basins (Fig. 10a, b). The catchment areas forthe individual types of load differ in the Partnachsystem. The area feeding the karst spring (Partnachur-sprung) has to be added to the contributing area fordissolved load (total contributing area for dissolved load28.12km2). On the other hand, the catchment areaupstream of the landslide dam of the Vordere BlaueGumpe (Fig. 3) has to be subtracted from the total areadownstream of the karst spring when calculating bedload yield. The contributing area for bed load yield isonly 4.82km2.

Owing to the different discharge characteristics (Fig.8) of the individual years sediment yield differs between

Fig. 9. Hydrograph and SSC distribution during the 2003 May 31

the observation periods (Fig. 10). In the limestone-dominated and disconnected system of the Partnachdissolved load output is predominant in the entiremeasuring period. Solid load output accounted for lessthan 10% of total sediment export in 2001, but for about25% in 2002, when peak discharges were higher. In thedry year 2003 solid load was less than 5%. It must benoted that the instruments failed in the Partnach duringthe peak discharges of that year.

In the connected system of the Lahnenwiesgrabenwith throughput of solid load, suspended load and bedload output are much more important with almost 60%of total load in 2001, more than 80% in 2002, and morethan 90% in 2003. The percentage of solid load for 2002and 2003 is most probably much higher, because duringextreme discharges it was not possible to apply themanually operated Helley–Smith sampler.

The particle-size distribution of the suspendedmaterial varies during flood events as the example of

st and June 1st flood event in the Lahnenwiesgraben river.

Fig. 10. Mean daily sediment yield of the Partnach river (a) and Lahnenwiesgraben river (b). The observation periods (2001–2003) have differentdurations. Therefore sediment yield is expressed in kg day−1 km−2.


the May 31st and June 1st event shows (Fig. 11). Thehighest amount of clay particles (52%) occurred close tothe flood peak, shown by the upper cumulativefrequency distribution (Fig. 11). Clay particles werederived from debris-flow material input. The maximumSSC in the Lahnenwiesgraben with 131g l−1 occurredduring the June 21st event in 2002 with a peak dischargeof 25.1m3 s−1. This event was accompanied by anumber of debris flows in tributaries. This maximumSSC is almost an order of magnitude higher than themaximum values of SSC in the national observation netin Germany.

4.3. Effective discharge

Effective or dominant discharge is defined as theflow or flow class which performs most work in terms ofsediment transport (Wolman and Miller, 1960). Thereare other definitions of dominant discharge, which areseen in the light of the influence on geomorphological

channel parameters (Knighton, 1998). This paperfollows the original concept of Wolman and Miller, inwhich effective discharge is the water discharge thattransports more sediment than any other discharge (seealso Emmett and Wolman, 2001). For the determinationof effective discharge information on the magnitude andfrequency of water flow and material transport must beavailable. In most cases effective discharge has beendetermined for bed load transport (Biedenharn et al.,2000; Emmett and Wolman, 2001).

Effective discharge may be calculated separatelyfor the different types of sediment transport (dis-solved load, suspended load, bed load) and also, inan integrated approach, for total load. In this paperboth approaches are followed. In Fig. 12 effectivedischarge calculations and characteristics are shownfor the 3-year observation period. It must be notedthat the calculation of effective discharge is notbased on full annual series, it is restricted to fieldseason flow (April to December, see Fig. 8) and thus

Fig. 11. Cumulative frequency distributions of particle size of the suspended sediments for the May 31st and June 1st 2003 flood event in theLahnenwiesgraben river. The central graph shows the mean particle size distribution for all samples taken during the event. The upper envelope showsthe distribution during the flood peak, the lower envelope during the recession limb of the flood (cf. Fig. 9).


mainly to events triggered by frontal or convectiverainfall.

In the Partnach river (Reintal) effective discharge fortotal load is found in low flow classes close to meandischarge (Fig. 12b), because sediment output isdominated by dissolved load, which has its maximumefficiency at low and moderate discharges (Fig. 12a).Solid load output plays a minor role in the buffered anddisconnected system of the Reintal, which does notallow throughput of solid load. It is most effective atabout 4.5m3 s− 1, which is approximately two times themean discharge. A more general discussion of therelations of effective discharge to mean or bankfulldischarge and the respective return periods is found inWard and Trimble (2004).

In the Lahnenwiesgraben, however, most work isdone by discharges much higher than mean dischargeduring extreme individual flood events (Fig. 12c, d).More than 70% of the total solid load of an observationperiod can be transported in a single flood. But thegreatest suspended sediment loads were not carried bythe highest discharge classes above 25m3 s− 1. Theywere transported by extreme events that occurred onJune 21st 2002 reaching about 22 and 25m3 s− 1. On thisday two rainstorms triggered a number of debris flows intributaries of the Lahnenwiesgraben (Haas et al., 2004),which supplied the fluvial system with exceptionalsources for suspended load. After these debris-flowevents higher sediment yields were measured in thetributaries (Haas et al., 2004), which also caused high

suspended sediment output from the whole catchment inthe 2002 observation period (Fig. 10b).

5. Discussion and conclusions

Though the catchments Reintal and Lahnenwies-graben are located in approximately the samephysiographic and climatic setting, their sedimentoutput and sediment transport attributes are verydifferent. The Partnach river in the Reintal isdominated by dissolved load output. Solid loadplays only a minor role. The system is disconnected,because landslide dammed lakes retain solid load.The conceptual model of connectivity of coarsesediment in stream channel systems developed byHooke (2003) can be applied for each subcatchmentin the Reintal valley. The system is buffered, aslarge parts of the basin are controlled by karsthydrology with relatively long retention times(Wetzel, 2004). In the Lahnenwiesgraben, on theother hand, solid load transport is predominant andthe absolute sediment yieldismuchhigher(Fig.10aandb). On a larger regional scale in the southwestern USASchmidt (1985), was able to demonstrate that suspendedsediment yield and the proportion of mechanical denuda-tion, compared to chemical denudation, increases withincreasingrunoffvariability.

The basins differ fundamentally in the absolute andrelative amounts of the individual sediment load typesand also in total load attributes. It becomes obvious that


measuring results from a single catchment cannot beregionally extrapolated to other basins in the vicinitywithout having more detailed information on litholog-ical attributes and on runoff and sediment transferconditions with respect to connectivity and buffering.This holds especially true for catchments in highmountain environments.

Fig. 12. Total dissolved solids, suspended sediment load, bed load as well as(a, b) and the Lahnenwiesgraben river (c, d). The diagrams are based on dataSection 3.2.

In small mountainous catchments the quantitativedetermination of a correlation between discharge andSSC poses considerable problems, because of theuncertainly associated with the temporal and spatialvariability of controlling factors such as precipitationamount, duration, intensity and spatial extent, availabil-ity of sediment sources, changes in the differential

total load and frequency of the discharge classes for the Partnach riverfrom the total observation period, for methods of load calculation see

Fig. 12 (continued).


activity of contributing areas and changes in hydraulicboundary conditions (Becht, 1989; Bley and Schmidt,1994; Ergenzinger and Schmidt, 1994; Johnson andWarburton, 2002; Unbenannt, 2002). One possibility forapproaching the problem is to determine event-specificrating curves (cf. Fig. 5). But these rating curves areonly defined for one individual event and cannot betransferred to other events in the discharge record.

Longer term extrapolations of sediment loads are notpossible with this approach.

Highest suspended sediment concentrations aremeasured during events which are triggered by extremerainfall and accompanied by debris flows on the slopesand in the tributaries of the system. This type of eventalso brought highest SSC values in a catchment in theItalian Dolomites (Lenzi and Marchi, 2000). Debris-

Fig. 13. Relation of event peak discharge and suspended sediment load in the Lahnenwiesgraben river.


flow material is transferred into the stream channel anddramatically increases suspended sediment transport.The debris flows supply the river with fine sediment,which normally is not available in the river bed. In 2002,which was the year with the greatest debris-flowactivity, the highest solid load export was registered.The link between debris flows and fluvial transportgives evidence of the connection between slope,tributary and river systems.

In the Lahnenwiesgraben there is a 17-year longdischarge record at the Burgrain gaging station at thebasin outlet (Fig. 1). For our observation periods,which included a total of 55 events, a reliable andhighly significant correlation (correlation coefficient:rPearson=0.9, significant at the 0.001 level) betweenevent peak discharge and the suspended sedimentload transported during the respective event wasfound (Fig. 13). This method of estimating eventsuspended sediment transport by using peak dischargeas a predicting variable has been tested before in anAlpine catchment by Becht (1989), yet on the basis ofa much smaller number of events. For the Lahnen-wiesgraben gaging station the discharge data of thelong record will be used to calculate long termsuspended sediment output variations and relatedclimatic and environmental controlling factors in futureresearch.

Acknowledgements

The study is financially supported by the DeutscheForschungsgemeinschaft (German Science Foundation).

For the field campaigns driving permissions from theForstamt Garmisch-Partenkirchen and cars from theMartin-Luther-University were made available. Specialthanks go to the other members of the SEDAG group fortheir helping comments, and last but not least to ourgraduate and post-graduate students (Sebastian Fuchs,Antje Krause, Holger Redlich, Ingo Sahling, MarkusWitzsche) for their active assistance during the fieldcampaigns.

References

Becht, M., 1989. Suspended load yield of a small Alpine drainagebasin in Upper Bavaria. Catena, Suppl. 15, 329–342.

Biedenharn, D.S., Copeland, R.R., Thorne, C.R., Soar, P., Hey, R.D.,Watson, C.C., 2000. Effective Discharge Calculation. A PracticalGuide. Technical Report. U.S. Army Engineer Research andDevelopment Center, Vicksburg.

Bley, D., Schmidt, K.-H., 1994. Schwebstofferfassung über dieTrübungsmessung in einem Wildbach (Lainbach/Oberbayern).In: Barsch, D., Mäusbacher, R., Pörtge, K.-H., Schmidt, K.-H.(Eds.), Messungen in fluvialen Systemen. Feld-und Labormetho-den zur Erfassung des Wasser-und Stoffhaushalts. Springer,Heidelberg, pp. 159–172.

Bunte, K., 1999. Scale considerations and the detectability ofsedimentary cumulative watershed effects. National Council forair and stream improvement. Technical Bulletin 776. ResearchTriangle Park, NC.

Campbell, F.B., Bauder, H.A., 1940. A rating curve method fordetermining silt-discharge of streams. Trans.-Am. Geophys. Union21, 603–607.

Emmett, W.W., Wolman, M.G., 2001. Effective discharge and gravel-bed rivers. Earth Surf. Processes Landf. 26, 1369–1580.

Ergenzinger, P., Schmidt, K.-H. (Eds.), 1994. Dynamics andGeomorphology of Mountain Rivers. Lecture Notes in EarthSciences, vol. 52. Springer, Berlin.


Gomez, B., Church, M., 1989. An assessment of bed load sedimenttransport formulae for gravel bed rivers. Water Resour. Res. 25,1161–1186.

Haas, F., Heckmann, T., Wichmann, V., Becht, M., 2004. Change offluvial sediment transport rates after a high magnitude debris flowevent in a drainage basin in theNorthern LimestoneAlps, Germany.In: Golosov, V., Belyaev, V., Walling, D.E. (Eds.), SedimentTransfer through the Fluvial System. Proc. Moscow Symp. August2004. IAHS Publ., vol. 288. IAHS Press, Wallingford, pp. 37–43.

Hirtlreiter, G., 1992. Spät-und postglaziale Gletscherschwankungenim Wettersteingebirge und seiner Umgebung. Münch. Geogr.Abh., B 15 (München).

Hooke, J., 2003. Coarse sediment connectivity in river channelsystems: a conceptual framework and methodology. Geomorphol-ogy 56, 79–94.

Johnson, R.M., Warburton, J., 2002. Annual sediment budget of a UKmountain torrent. Geogr. Ann. 84A, 73–88.

Keller, D., Moser, M., 2002. Assessments of field methods for rock falland soil slip modelling. Z. Geomorphol., Suppl.Bd 127, 127–135.

Knighton, A.D., 1998. Fluvial Forms and Processes. A NewPerspective. Arnold, London.

Lenzi, M.A., Marchi, L., 2000. Suspended sediment load during floodsin a small stream of the Dolomites (northeastern Italy). Catena 39,267–282.

Martin, Y., 2003. Evaluation of bed load transport formulae using fieldevidence from the Vedder River, British Columbia. Geomorphol-ogy 53, 75–95.

Miller, H., 1961. Der Bau des westlichen Wettersteingebirges. Z.Dtsch. Geol. Ges. 113, 161–203.

Morche, D., Schmidt, K.-H., 2005. Particle size and particle shapeanalyses of unconsolidated material from sediment sources andsinks in a small Alpine catchment (Reintal, Bavarian Alps,Germany). Z. Geomorphol., Suppl.Bd 138, 67–80.

Morche, D., Katterfeld, C., Fuchs, S., Schmidt, K.-H., in press. Thelife-span of a small high mountain lake, the Vordere Blaue Gumpein the Bavarian Alps. - IAHS Publications, Wallingford, IAHSPress.

Rickenmann, D., 1997. Sediment transport in Swiss torrents. EarthSurf. Processes Landf. 22, 937–951.

Schmidt, K.-H., 1984. Der Fluß und sein Einzugsgebiet. Hydro-graphische Forschungspraxis. Steiner, Wiesbaden.

Schmidt, K.-H., 1985. Regional variation of mechanical and chemicaldenudation, Upper Colorado River Basin, USA. Earth Surf.Processes Landf. 10, 497–508.

Schmidt, K.-H., Vetter, T. (Eds.), 2002. Late Quaternary Geomorpho-dynamics. Z. Geomorphol., Suppl.Bd, vol. 127. GebrüderBornträger, Berlin.

Schmidt, K.-H., Bley, D., Busskamp, R., Ergenzinger, P., Gintz, D.,1992. Feststofftransport und Flußbettdynamik in Wildbachsyste-men—Das Beispiel des Lainbachs in Oberbayern. Die Erde 123,17–28.

Schrott, L., Niederheide, A., Hankammer, M., Hufschmidt, G., Dikau,R., 2002. Sediment storage in a mountain catchment: geomorphiccoupling and temporal variability (Reintal, Bavarian Alps,Germany). Z. Geomorphol., Suppl.Bd 127, 175–196.

Schrott, L., Hufschmidt, G., Hankammer, M., Hoffmann, T., Dikau,R., 2003. Spatial distribution of sediment storage types andquantification of valley fill deposits in an Alpine basin, Reintal,Bavarian Alps, Germany. Geomorphology 55, 45–63.

Unbenannt, M., 2002. Fluvial sediment transport dynamics in smallalpine rivers—first results from two Upper Bavarian catchments.Z. Geomorphol., Suppl.Bd 127, 197–212.

Walling, D.E., 1977. Assessing the accuracy of suspended sedimentrating curves for small basins. Water Resour. Res. 13, 531–538.

Ward, A.D., Trimble, S.W., 2004. Environmental Hydrology. LewisPublishers, Boca Raton.

Wetzel, K.-F., 1994. The significance of fluvial erosion, channelstorage and gravitational processes in sediment production in asmall mountainous catchment area. In: Ergenzinger, P., Schmidt,K.-H. (Eds.), Dynamics and Geomorphology of MountainRivers. Lecture Notes in Earth Sciences, vol. 52. Springer,Berlin, pp. 141–160.

Wetzel, K.-F., 2004. On the hydrology of the Partnach area in theWetterstein Mountains (Bavarian Alps). Erdkunde 58, 172–186.

Wilcock, P.R., 2001. Toward a practical method for estimatingsediment-transport rates in gravel-bed rivers. Earth Surf. ProcessesLandf. 26, 1395–1408.

Wolman, M.G., Miller, J.P., 1960. Magnitude and frequency of forcesin geomorphic processes. J. Geol. 68, 54–74.

Zanke, U., 1982. Grundlagen der Sedimentbewegung. Springer,Berlin.

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