Do high‐resolution fan delta records provide a useful tool for hazard assessment in mountain regions?

At present, the significance of flood magnitude, frequency and triggering forces in mountain regions is also being discussed in the context of Global Change (Kääb et al., 2005). Since the 2005 Lütschine flood event, these variables have also been considered on a local scale. The Alps are especially sensitive to changes in the circulation of the atmosphere at global scale and to events of extreme precipitation and floods. Floods are known to have resulted from extreme rainfall intensity and frequency, snow melt, glacier outburst, precipitation combined with frozen soils, landslide, lake outburst flood and other phenomena. Land use can modify considerable mountain ecosystems and river dynamics (Glaser et al., 2005).

The determination of recurrence intervals is crucial for flood hazard analysis, risk assessment and mitigation strategies (Gees, 1997; Dickau and Pohl, 2007). Data series of alpine instrumental hydrological measurements only exceptionally exceed the last 100 years and therefore they poorly record centennial climate variability. The flood reconstruction from documentary sources as chronicles, annals, paintings and flood marks provides data of the last 700 years (Pfister, 1999; Glaser, 2001), whereas the study of previous Holocene environmental variability and palaeofloods requires the use of sedimentary records as lake sediments, overbank, channel and slackwater flood deposits, etc. (Glaser et al., 2005).

Fluvial sedimentation is discontinuous in time and space, and sediments may be eroded by subsequent reworking phases. Despite the resulting discontinuity of sediment records, specific fluvial archives such as fan delta deposits provide accurate data about terrestrial environmental change, including changes in the hydrological regime and sediment supply (Migowski et al., 2006).

The multidisciplinary Fluvalps‐3000 research project addresses the influence of external factors, such as climatic variability and land use, on aggradation processes and palaeofloods. The variability of fluvial environments of the Lütschine catchment in the Swiss Alps during Late Holocene is traced from fan delta deposits using a multi‐proxy approach integrating data from other case studies of fluvial environments in the Alps. Furthermore, this paper aims to provide local authorities with an overview of the usefulness of flood data to assess flood hazards. With regard to the discussion about future extreme events as a consequence of present day global warming, palaeoenvironmental sciences could provide an outstanding contribution: do past extreme floods occurred during warmer, cooler climate or climatic transition?

Since the retreat of the Aare glacier system during the Late Glacial period, the Lütschine has been draining the northern slope of the Jungfrau massif and the Lombach river the alpine flysch landscape north of the Harder ridge to the Aare River. Both river systems have built up fan deltas (46°40′N, 7°53′E; 4,158 m a.s.l.) that separate Lake Thun from Lake Brienz (Figure 1). Layers of fluvial gravel, sand and silt intertongue with organic‐rich fine material and peat horizons. Recently, the water levels of Lake Brienz at 563.70 (+1.63/−1.25) m a.s.l. and Lake Thun at 557.66 (+1.64/−0.9) m a.s.l. define the base level of erosion of the Lütschine river and Lombach river.

Alpine‐type glaciers (e.g. lower Grindelwald glacier) and smaller hanging glaciers (e.g. Eiger glacier) cover 17.4 per cent of the 379 km² Lütschine catchment. In the northern Swiss Alps, floods, such as the 2005 Lütschine flood (264 m³s⁻¹), were triggered by precipitation anomalies, pronounced snow melt caused by warm fronts, and glacier outbursts. The lithology of the drainage basin can be subdivided into three major areas: The northern area, with elevations below 2,100 m a.s.l., mainly made up of carbonated rocks; the central sector, with maximum elevations between 2,343 and 2,928 m a.s.l., consisting of carbonated rocks, sandstones and marls; and the southern part, with limestone at lower altitudes and crystalline rock reaching up to 4,158 m a.s.l. in the summit area of the Aare Massif.

The smaller Lombach catchment with a surface of 48 km² shows a different topographic configuration. Highest elevations of the catchment do not exceed 2,085 m a.s.l. and no glacier persisted during the Holocene. Lithology of the Lombach basin is dominated by flysch deposits mainly formed by marls, limestones and sandstones. Pleistocene moraine material is also present in north facing slopes. The Lombach river is controlled by a nivo‐pluvial regime.

The research project on fluvial variability in the Swiss Alps combines different methods from several disciplines such as sedimentology, geomorphology, geography, palynology and geochronology (Schulte et al., 2007, 2009). This paper focuses on sedimentological and geocronological methods applied to the fluvial records of key section IN‐2 and core IN‐16 located in the central area of the Lütschine fan delta and to the sedimentary record of key section LB‐10 of the Lombach fan delta (Figure 1).

The alluvial fan deposits were sampled at various intervals. The core IN‐16 was sampled at 1 cm resolution from 560 to 270 cm depth. Above 270 cm, the fan deposits are exposed in a 30 m wide section (profile IN‐10). According to the continuous lateral extension of the lithostratigraphical units, the IN‐10 section can be traced to the 120 m wide and 330 cm thick IN‐2 outcrop (Figure 2) which shows a well differentiated sequence of peat and organic‐rich horizons, gastropod‐rich silty beds, silt layers, sand beds and coarse grained channel deposits.

The sedimentological units of the upper part (from surface to 120‐240 cm depth) of the key section LB‐10, located at the lower middle area of the Lombach fan delta, were traced horizontally in a 180 m‐wide trench. The lower units (up to 420 cm depth) were studied from several cores. By contrast to the Lütschine sections, the Lombach sequence shows frequent shallow gravel channel deposits that interfinger fine‐grained sandy alluvial and silty organic rich sediments.

Sediments and soil horizons were described, and trunk, plant and mollusc fragments were collected and classified. To study the geochemical variability of the alluvial fan sediments, major and trace elements of 48 samples extracted from the IN‐2 key section and 95 samples from the LB‐10 key section were determined by conventional X‐ray fluorescence (XRF) using a Philips PW 2400 spectrometer. With regard to the geochemical record of the IN‐16 core, Ca, Ti, K, Fe, Cu and Sr were determined at the Geosciences Department of the University of Bremen using a XRF spectroscopy core scanner according to Jansen et al. (1998). Organic carbon (OC) was performed by loss on ignition (LOI). Radiocarbon dates were calibrated using the CALIB 5.0.2 Program (Stuiver et al., 2005).

Finally, the obtained alluvial fan proxies, i.e. lithology and geochemistry were correlated with global proxies such as ¹⁴C residuals (Reimer et al., 2004).

Several logs were obtained from the central Lütschine fan delta. Key section IN‐2 and the core IN‐16 (Figure 2) record the aggradational evolution during the last 3,500 year. Figure 3 shows the lithology, the obtained radiocarbon ages, the Ca/Ti relationship, the Ca content reported as CaO percentage for IN‐2 and as counts per second (cps) for IN‐16, the Cu content as ppm for IN‐2 and as cps for IN‐16, and the percentages of OC.

The radiocarbon dates were used for the chronological model of the aggradational pulses. The four radiocarbon ages obtained from the bottom and top of the two thicker peat layers of IN‐2 provide information about the elapsed time without accumulation (bottom and top of the same peat layer) and the elapsed time between the occurrence of an aggradation and the formation of the next peat layer. According to these dated samples about 15 cm of peat were deposited between 40 and 90 years, whereas a period of 70 years was required to re‐establish similar peat environments after deposition occurred.

The lithology (Figure 3) shows the different aggradational pulses characterized by predominant upward thinning sequences where the organic beds correspond to relativly stable conditions in the general aggradational dynamics of the Lütschine fan delta. Gravel beds correspond to channel or crevasse splay deposits whereas sand and silt are interpreted as overbank deposits.

The calcium content shows its lower values during the peat deposit formation, probably due to the acidic waters of these environments, whereas its higher values correspond mainly to silty deposits. The Ca/Ti in general, highlights the gravel deposits probably as a consequence of grain size distribution because the Ti content is closely related to fine phyllosilicates (Schulte et al., 2009). This fact evidences minor aggradational pulses inside the overbank deposits which are characterized by the progressive decline in the Ca/Ti and a slight increase in organic matter at the top of each pulse.

The Cu content is used here as an indicator of major mining activity in the Lauterbrunnen Valley (lead, zinc, iron and baryte mining). In steep mountain areas, mining can supply large amounts of incoherent material, which can easily be introduced to the river channel. Nevertheless, the high‐Cu content can be also interpreted as a consequence of pyrite oxidation and the formation of acidic waters, mainly during peat formation. Thus, the high‐Cu content in peat beds is not taken into account as an indicator for mining.

The OC content (OC in Figure 3) was drawn in logarithmic scale due to the high‐values recorded in the peat layers compared with the low values found in sandy or silty beds. The peaks of organic matter, correlating to the minima values in Ca/Ti, were used to model the main aggradational pulses.

At least seven major aggradation pulses can be differentiated from the bottom to the top (Figure 3):

• 1.

  Pulse I. (Figure 3, Ca/Ti anomalies log): from the gravel bed recorded at 5.3 m depth in the IN‐16 core to the organic layer dated at 3,005±35 yr BP.

• 2.

  Pulse II. From 3,005±35 yr BP to the organic layer dated at 2,700±45 yr BP. During this aggradational period four minor pulses can be differentiated on the base of Ca/Ti and OC content.

• 3.

  Pulse III. From 2,700±45 yr BP to the peat layer dated at 2,305±45 yr BP. Ca/Ti content show five minor aggradational pulses.

• 4.

  Pulse IV. From 2,305±45 yr BP to the peat layer dated at 1,980±30 yr BP. During this period, the lithology differentiates three further aggradational pulses. The occurrence of four peaks of Cu content suggests mining activities in the Lütschine catchment. The upper metal anomaly could be related to the Roman mining activities found in the Alps (Morin et al., 2007).

• 5.

  Pulse V. From 1,980±20 yr BP to the peat layer dated at 1,650±20 yr BP. The upper part of this main pulse is characterized by the occurrence of two thick peat layers separated by silts which represent a flood event. Two more pulses can be differentiated by the lithology and Ca/Ti. The Cu content is the highest of the section although its interpretation could be ambiguous due to the peat formation.

• 6.

  Pulse VI. From 1,650±20 yr BP to the peat layer dated at 1,160±20 yr BP. Ca/Ti relations also suggest the occurrence of four minor pulses not reflected by OC oscillations. The copper content peaks at the beginning of the eighth and ninth centuries, suggesting middle ages mining activities in the Lütschine catchment.

• 7.

  Pulse VII. From 1,160±20 yr BP to the top of profile IN‐2. No sensitive aggradation pulses were recorded. Land use changes related to the establishment and prosperity of the Monastery of Interlaken in 1133 AD (Affolter et al., 1990), detected by pollen records from site IN‐2 (Schulte et al., 2009), and channel management changed the sedimentation pattern.

Lithological and geochemical studies consisting of macroscopic description of soils and sediments, loss on ignition and mayor elements by XRF were carried out also in the lower central area of the Lombach fan delta where the fan deposits are exposed in a 180 m‐wide trench (Figure 2). The 4.3 m high outcrop was sampled at intervals from 3 to 5 cm providing the aggradation history for the last 3,000 cal yr BP. Figure 3 shows the Ca/Ti relationship versus age cal BP and the main lithological units. The chronological model was obtained from five radiocarbon dates and artifacts.

The lithology and Ca/Ti ratio provide information about the aggradational pulses limited by low‐Ca/Ti values and by organic rich sediments. The lower Ca/Ti values correspond to a decalcification soil process such as can be observed in the top of the sequence where artifacts dated between sixteenth and nineteenth century were found. A radiocarbon age of 1,255±40 yr BP obtained at a relative shallow depth (−56 cm) suggests a large period of stability of this part of the fan delta. Similar low values of the Ca/Ti ratio related to soil processes were found at the following intervals: from 410 to 370 cm, from 230 to 215, and from 175 to 155 cm. During these intervals Ti and Al percentages show higher values due to their mayor stability, whereas Ca drops to minimum values.

The high values of the Ca/Ti correspond to high‐calcium carbonate content in predominant coarse‐grained flood deposits of the fan delta. These carbonate‐rich beds evidence erosion processes in the Lombach catchment mainly formed by marly flysch deposits.

Following the sedimentary model of the Lütschine fan delta four major aggradation pulses can be differentiated (Figure 3):

• 1.

  Pulse I. From the organic‐rich layer at the bottom of the sequence, dated at 2,710±40 yr BP to the organic layer determined with an age of 2,305±40 yr BP. The obtained logs show homogenously high Si, Al and Ti values and low Ca percentages which mask minor aggradation pulses as recorded in the middle part of the Lombach profile. However, the major pulse I of the Lombach section can be correlated clearly with phase III of the Lütschine fan delta.

• 2.

  Pulse II. From 2,305±40 yr BP to the organic‐rich horizon dated at 1,685±40 yr BP. Four aggradation pulses are shown by the Ca/Ti plot (Figure 3) and coarse‐grained layers. The decrease of the Ca/Ti ratio at 2,000 cal yr BP may correspond to the boundary between phases III and IV in the Lütschine fan sequence.

• 3.

  Pulse III. The organic layer dated at 1,685±40 yr BP and the peat horizon dated at 1,545±40 yr BP are only separated by two minor aggradation phases. The lower organic layer correlates to the upper peat horizon of the Lütschine fan pulse V.

• 4.

  Pulse IV. From 1,545±40 yr BP to the week organic layer dated at 1,255±40 yr BP correlates to the Pulse VI of the Lütschine section. The Ca/Ti curves of both sections show four minor aggradation pulses.

The upper section from 1,255±40 yr BP to the top may record a further aggradation pulse. However, the lack of precise radiocarbon dates difficultates the determination of the chronological framework. The abrupt decrease of the local sedimentation rate from 3.7 mm yr⁻¹ of pulse IV to 0.4 mm yr⁻¹ in the upper section and the decalcification of the top soil, indicate clearly the switch of the sedimentary pattern form an active flood plain system to a nearly stable land surface. This change and the position of the section on the margin of the slightly higher level of the eastern Lombach fan, evidence the shift of the active channels toward the western fan area after 1,255±40 yr BP.

Sedimentary architecture and facies analyses from chronologically constrained sections provide useful data in defining the environmental variables that control the evolution of the Lütschine and Lombach catchment. Figure 3 shows the composite lithological sections (IN‐2 plus IN‐16; LB‐10), the Ca/Ti anomaly, the Cu anomaly and the OC content compared with the global climate record of ¹⁴C residuals (Reimer et al., 2004).

Tectonics and climate are the primary variables considered in conceptual models of alluvial fan development. However, in areas formed by glaciers, such as the Lütschine and Lombach catchment areas, glacier dynamics and outbursts, landslide lake outburst, shifts in vegetation densities, snow melt and rainfall regime seem to be the main variables involved in alluvial fan evolution. Channel profile changes can also be triggered by isostatic re‐adjustments on the basis of a large time scale and, furthermore, by lake level changes.

Taking the collected data into account, the following facts can be highlighted (Figure 3):

• 1.

  According to radiocarbon dates and lateral extension of lithology, major entrenchment phases are negligible at the studied sites during the last 3,600 yr.

• 2.

  The gravel deposits mainly occur during positive ¹⁴C residuals (Reimer et al., 2004), suggesting more frequent floods during cold periods. The five flood episodes detected during the last two millennia correlate with periods of increased debris flow events recorded by turbiditic layers in lake deposits in the Dolomite Alps (Irmler et al., 2006) and in the Lower Tauern (Schmidt et al., 2002). These cold phases were also detected in stalagmite records from the central (Mangini et al., 2005) and southeastern Alps (Frisia et al., 2005).

• 3.

  The major aggradational pulses of the Lütschine fan occur at intervals from 580 to 200 years, whereas in the Lombach catchment intervals range from 350 to 120 years.

• 4.

  At least 19 minor aggradational pulses are reported in the Lütschine catchment at a medium recurrence interval around 116 years at least from 3,005±35 yr BP until 1,160±20 yr BP and in the Lombach basin ten pulses at an average interval of 105 years. These deposition events could be seen as return period of moderate flood intensity while catastrophic events could be related to the mayor 580‐200 years periods (average interval of 370 years) in the Lütschine catchment and 350‐120 years periods (average interval of 262 years) in the Lombach catchment. The minor pulses occurring at intervals between 70 and 150 years could be related to solar forcing cycles detected at centennial scale, such as the Gleissberg cycle, in other sedimentary records (Castagnoli et al., 1994; Versteegh, 2005).

• 5.

  Despite the different fluvial regimes, glacio‐nival regime of the Lütschine river and pluvio‐nival of the Lombach river, the following correlation can be pointed out (Figure 3):

  • synchronous trends of the Ca/Ti ratios;

  • major flood events at 2,250, 2,100, around 1,850 and at 1,300; and

  • formation of organic‐rich horizons and peat at 2,820, 2,300, 1,600 and 1,450 yr cal BP.

The regional correlation of Alpine fluvial archives shows a different picture. Sedimentological and geomorphic studies on alluvial fans, considered as a system of sediment storage in alpine catchments, have been conducted in the High Tauern (Veit, 1988), Inn Valley (Patzelt, 1994), Ötztal Alps (Geitner, 1999), Retic Alps (Burga et al., 1997), Allgäu Alps (Jerz et al., 2000) and the Bavarian Alps (Schrott et al., 2002). The chronologies of Alpine fluvial stratigraphies show a heterogeneous pattern of geomorphic processes due to the following factors: differences in time resolution, configuration of catchments, different environmental forces, and spatial distribution and intensity of rainfall events. However, the sedimentary archive of the Isola fan delta in the Retic Alps records similar aggradation processes during the colder climate phases (Göschen I and Göschen II period) and peat formation dominance during the Roman Climate Optimum (Burga et al., 1997).

All these facts indicate that the main variable controlling the Lütschine and Lombach fan evolution is climate.

Palaeoecological studies can be a useful tool to provide datasets for risk assessment of flood hazards (Dickau and Pohl, 2007). During 23 August of 2005 the Lütschine river reached the historical maximum discharge of 264 m³ s⁻¹ recorded since 1920 by the gauge station at Gsteig. Economic losses in the Lütschine catchment amount to 211 million CHF.

Despite the catastrophic impact of the 2005 flood – aggradation areas of fan channels can be traced from the SPOT image shown in Figure 1, documentary sources dated before the instrumental data series, recorded several catastrophic floods during the last 500 years. The flood inventory of Lehmann and Naef (2003) reports that the most severe flood of the last 200 years probably occurred on 9 August of 1831. Another extreme event occurred on 16 May of 1528 causing severe destruction in villages located on the fan delta (Zwahlen, 1981). These events can be correlated with gravel layers in the Lütschine key sections (Schulte et al., 2009).

Flood recurrence intervals were calculated by Department of Engineering of the Canton Bern (Jäggi et al., 2007) to assess the Lütschine flood of 2005. Based on the discharges measured from 1923 to 2005 a recurrence interval of 300 years was assigned. However, the authors showed that the recurrence interval becomes shorter, about 100 to 200 years, if the calculation includes only the hydrological data from 1976 to 2005, due to the increased flood magnitude and frequency during these three decades. Therefore, the authors pointed out the difficulty to assess future flood dynamics.

The assessment of the recurrence interval of the Lütschine flood from our palaeoenvironmental data result difficult as well. One of several reasons is the fact that modern infrastructures as motorways, bridges, railways, etc. modify substantially the way of the ramified shallow shaped delta channels. Therefore, the sedimentation conditions in the key section area have changed and no valid sedimentary proxy data of the 2005 flood were provided. However, the SPOT images (Figure 1), pictures taken during the flood and subsequent mapping of flooding processes shows that several palaeochannels mapped by our field work in 2002 (the geomorphological map was presented on the INQUA Congress in 2003) were reactivated. Furthermore, river channel control by embankment was applied on the Lütschine fan with more or less success during centuries (Vischer, 1989). Pollen data from key section IN‐2 show a strong human impact by land use on local woodland from AD1000 (Schulte et al., 2009) to the end of the nineteenth century and Cu logs indicate mining activity in the Lütschine catchment, thus modifying the fluvial aggradation pattern as shown by the Ca/Ti anomalies.

Despite the methodological limits of our multiproxy research, our studies may contribute some evidence regarding the characterization of the 2005 flood in the Lütschine catchment. As discussed in the previous chapter, our sedimentary data from fan delta records show mayor Lütschine floods at an average recurrence interval of 370 years (between 580 and 200 years, Figure 3) and minor floods occurring at intervals between 70 and 150 years (average period of 116 years). As argued before it is difficult to classify the 2005 flood as one of the major or one of the minor floods. However, our data indicate that mayor floods over the last 3,600 years coincide predominantly with positive radiocarbon anomalies (decreased solar activity) and cold phases in the Alps. The Lombach fan delta aggradation developed a similar sedimentary pattern. But in fact, the 2005 flood occurred in both river systems during one of the warmest periods of the Holocene.

The collected data are supported by the historical reconstruction of floods frequencies of the Alpine Rhine, Rhone and Reuss rivers of the last 500 years undertaken by Pfister (1999). Clusters of mayor floods occurred during cooling of the Little Ice Age from AD1550 to AD1580 and from AD1827 to AD1875, although periods without flooding (AD1641 to AD1706) are also recorded during cold periods as the Maunder Minimum. Such pattern in regional flood response has also been shown by the flood calendar of Swiss rivers compiled by Gees (1997) making use of documentary sources and instrumental measurements. The author showed that extreme events in Swiss river basins over the period from 1800 to 1975 occurred predominantly during years with lower annual mean temperatures (particularly about 1880 and 1915), but after 1975 this pattern changed. With regard to the control of geomorphic processes in alpine headwaters, Stoffel et al. (2008) conclude from dendrochronological studies on a debris‐flow cone in the Valais (Swiss Alps) that periods of enhanced debris‐flow activity from the 1570s to the 1860s correspond to cool summers with frequent snowfall at higher elevations.

According to these evidences the Lütschine flood in 2005 may not be considered necessarily as one of the mayor catastrophic events. In addition, the ongoing research on historical flood levels reconstruction from written sources and the location of historical buildings in the apex area of the Lütschine fan delta (not discussed in this paper) provide preliminary evidences, that the magnitude of the warm climate pulse 2005 flood was considerable smaller than the 1831 flood during the Little Ice Age. Thus, the Fluvalps‐3000 project provides useful data for local authorities involved in future flood risk assessment. For example, adjustment of hazard maps and new planning of emergency measures can be considered in the future as necessary actions.

It is proposed the solar influence on regional hydrological regime as the main factor triggering the flooding events in the Lütschine and Lombach catchments, a hypothesis which is substantiated by the observed correlation between the timing of mayor flood events and radiocarbon anomalies and the quasi‐cyclic Ca/Ti ratio of the analysed fan delta sediments. These findings match to the conclusions drawn by Versteegh (2005) in his review on solar forcing of climate derived from evidences from the past. He postulated that middle latitudes equatorward shift of the zonal circulation during solar minimum probably (co‐)induces wet and cool episodes in Western Europe. However, a clear link between solar activity and solar forcing based on physical processes is still missing as recently pointed out by Wanner et al. (2008) in their overview on mid‐to late Holocene climate change.

Albeit the uncertainties regarding forcing mechanism of fluvial environments and the geochronological limitations of fluvial sedimentary records, it is worth to mention that the presented 3,600‐year long flood proxy is unique in the European Alps.

These studies were funded by the Spanish Ministry of Education and Science (CGL2006‐01111) and by the Alexander von Humboldt‐Foundation (V‐3.FLF‐DEU/1070630). Conventional radiocarbon dating was carried out at the Radiocarbon Laboratory, Physics Institute, University of Bern and the authors thank Professor Thomas Stocker and René Fischer for their support.

The authors wish to thank Professor Ivan Mercolli (Institute of Geology, University of Bern) for the determination of major and trace elements by X‐ray fluorescence and Dr Daniel Gutscher and Dr Renate Ebersbach from the Archaeological Survey of the Canton Berne for the dating of the artifacts and archaeological background. The authors are also grateful to the Cantonal Office on Preservation of Historic Buildings and Monuments (Bern) and the Cantonal Office for Water and Geology (Bern) for the access to their data sets and archives.

L. Schulte is a Professor of Geomorphology and Paleoecology at the University of Barcelona and coordinator of the FluVAlps Research Group. His main research activities focus on paleoclimate and environmental records, human‐environment interaction, glacial and periglacial geomorphology, and soil science. L. Schulte is the corresponding author and can be contacted at: schulte@ub.edu

R. Julià is a Research Professor of Paleoecology and Quaternary Geology at the Institute of Earth Sciences Jaume Almera (CSIC, Barcelona). His fields of interest are geochronolgy, geochemestry, and paleoecological studies mainly based on lake sediments and travertine.

H. Veit is a Professor of Paleogeoecology, President of the Swiss Interacademic Commission for Alpine Studies (ICAS), and coordinator of the Paleogeoecology Research Group hosted at the University of Berne (Switzerland). His main academic interests are in the areas of geomorphology, soil science, and palaeoecology.

F. Carvalho is a postgraduate scholar of the Spanish Department of Education and Science and PhD student of the Department of Physical and Regional Geography, University of Barcelona. His PhD research covers the paleoenvironmental multi‐proxy analysis of Holocene fluvial sedimentary records in the Haslital (Aare catchment, Swiss Alps).