Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , and 1 on slopes and dis- ff , J. Llorca 4 , R. Julià 3 3392 3391 , T. Schmidt 1 O anomalies, cooler summer temperatures and phases of , F. Carvalho 18 2 δ O, tree-rings, NAO, SNAO) identify similar periodicities of around Ti) peaks and Factor 1 anomalies. Geomorphological, historical 18 / δ , J. C. Peña 1 5 Spectral analysis of the geochemical and documentary flood series and several cli- This discussion paper is/has beenSciences under (HESS). review Please for refer the to journal the Hydrology corresponding and final Earth paper System in HESS if available. Department of Physical Geography, University ofMeteorological Barcelona, Service Barcelona, of Spain Catalonia, Barcelona,Schmidt Spain Information- and Webdesign, Düsseldorf,FluvAlps Germany Research Group, University ofInstitute Barcelona, of Barcelona, Geography, University Spain of Bern, Bern, Switzerland mate proxies (TSI, Abstract A 2600 yr longdelta plain composite sediments palaeoflood ofAlps. record the Natural Hasli–Aare is proxies floodplain compiled reconstructed on fromdata the from sedimentary, were northern geochemical high-resolution calibrated and slope by geomorphological ofthan textual the 12 Swiss and of factual thenation sources 14 and of historically instrumental the recorded data.flood Hasli–Aare extreme No layers, events Correction fewer log(Zr between in 1480and 1875 and instrumental were the data also termi- estimations provide identified of evidence severe by and for coarse-grained catastrophic flood historical floods. damage intensities and discharge losilicates (from the medium high catchmentmaxima, area) match suggesting those reduced of flood Total Solar activityof Irradiance during clusters warmer of climate pulses. floodcatchment Aggradation area layers (plutonic with bedrock) increased1720 (e.g., contribution and 1300–1350, of 1811–1851 1420–1480, cal yr siliciclasts 1550–1620,solar AD) 1650– from irradiance, occurred the lower predominantly highest during periods with reduced 60, 80, 100, 120 andNorth 200 years Atlantic during circulation the last andfloodplain millennia, record solar indicating illustrates that the forcing periods influence on of of organic alpine the soil formation flood and dynamics. deposition of The phyl- composite drier spring climate insnow the patches Alps. susceptible Increased to waterabrupt melting storage rises processes by in associated glaciers, temperature with snowcharges substantially rainfall cover of increased episodes and alpine surface and run-o rivers.severe This and catastrophic interpretation historical is floods in inpositive the agreement SNAO Aare pulses with since after 1670 the occurred yearscooler findings mostly or annual during that temperatures. even the decades dominated by negative SNAO and H. Veit 1 2 3 4 5 Received: 26 February 2015 – Accepted: 3Correspondence March to: 2015 L. – Schulte Published: ([email protected]) 27 MarchPublished 2015 by Copernicus Publications on behalf of the European Geosciences Union. A 2600 year history ofBernese floods Alps, in Switzerland: the frequencies, mechanisms and climate forcing L. Schulte Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/12/3391/2015/ 12, 3391–3448, 2015 doi:10.5194/hessd-12-3391-2015 © Author(s) 2015. CC Attribution 3.0 License. 5 10 20 15 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ected by a flood ff cult to confidently ffi . Due to the unequal 2 3394 3393 200 years using short instrumental series, and > ects of climatic changes on alpine floods outside ff ects of land-use. In the context of global climate change, it is striking that the ff The aim of this paper is to reconstruct long time series generated from high- In contrast to urban gauging stations in the foreland (e.g., the Basel-Rhine station, Proxy data from sedimentary records such as lake sediments (Irmler et al., 2006; resolution floodplain sedimentswhich of reproduce the interdistributary fluvialin dynamic, basins including a of trends, medium-size clusters basin. thebut and Medium-size gaps may Hasli–Aare basins in also are delta, the not respondthe floods only investigation to of influenced the the by floodplain regionalcupation local dynamics and factors, and/or will integrate hydraulic global information managementfocuses climate about that human on variability. interact oc- Furthermore, the with Bernesereliable the information Alps, fluvial systems. on for The the twotorically study hydrological reasons: has risks firstly, been the incalibrating considered societal a geoarchives as densely demand by a populated for historicalwill flood area more sources test and which “hot the instrumental his- spot”; geochemical data.ries and flood Furthermore, provide secondly, proxies we information by the regarding applying possibilityvariability the spectral similar of frequencies analysis to if of theanalyses these hydrological and periodicities time and possible se- correlations environmental of contribute Late toing the forces Holocene understanding behind palaeoclimate of alpine the floods, proxies. possible and driv- These the mechanisms at work. spatial distribution of thetive precipitation rainfall events caused (due by for examplewhether summer to alpine thunderstorms the lake orientation and records of advec- variability. slopes), show the a question predominantly arises local of response to regional climate of lake sediments ratherWilhelm than et to al., 2012; those Wirthof of et the fluvial al., studies sediments 2013; in Glur (e.g.,2011) et Lake Magny and al., Bourget et Lake 2013). (Arnaud al., However, Brienz with etby 2010; (Wirth the small al., exception et catchments 2005), al., ranging Lake 2011) from Silvaplana most several (Stewart of hectares et to the al., a alpine few lakes km analysed are fed gap from AD 1937lar to climate AD pulses 1967 (e.g., (Gees,may 1997). during not The the be fundamental Little recorded problem Ice in is Age) these that and flood secu- low-frequency series. extreme For this events reason it is di assess floods with a return period of in operation since AD 1808)the data inner series Alps of only instrumental hydrological go measurements back in 100 years and many of the series are a the known range of extremedata. events reconstructed Continuous from high documentary resolution andments palaeohydrological of instrumental floods time and series debris flows from are terrestrial generally attributed sedi- to decadal and annual records Stewart et al., 2011;(Schulte Wilhelm et et al., al., 2012; 2008,data Wirth 2009a, for et the 2014; al., study Laigre 2013) of et and the al., flood potential plain 2013; e deposits Carvalho, 2014) can provide 1 Introduction Mountain regions like theexposed Alps to cover changes sensitive and inthe vulnerable atmospheric e ecosystems circulation, which extremeannual are mean meteorological temperatures in events, the and Alpstemperature have over increased three the times last moretrend than 100 years the is global (Hartmann not et dependentenvironmental al., on gradient, 2013). altitude with In (Hansen major general, et altitudinaland the al., limits so warming on, such 2010); makes as however, the the the alpine strong treeline, area the vertical very snowline, sensitive to climate changes. other methods need to be applied.sources For example, like flood chronicles, reconstruction annals, from paintings documentary land and over flood approximately marks the provides lastet data from 750 al., years Switzer- 2011) (Röthlisberger, encompassing 1991;Medieval Pfister, the Warm 1999; Period, latest the Wetter climatic Little cycles Ice of Age, and the the Holocene: 20th the century end warming. of the 5 5 15 20 25 10 15 10 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 m 6 -large 2 10 × at the summit level of the Aare massif. 1 at the Brienz gauging station, with a maxi- − 1 3396 3395 − and sediment volumes from 15 to 26 E; Fig. 1), located on the northern slope of the s 0 3 1 − 04 ◦ N, 6 being recorded on 22 August 2005. 0 1 − 41 ◦ s 3 1.25) ma.s.l., Lake Brienz defines the base level of erosion of the − 1.63/ at Interlaken to 2800 mmyr + 1 − In the northern Swiss Alps, floods have mainly been triggered by precipitation In spite of the potential geographical marginality of high mountain regions such as At 563.70 ( Catchment lithology (Fig. 1) is an important issue for the interpretation of geochem- The present alpine geomorphology shows a high diversity of complex connected lake outburst floods (Gees, 1997;1175 mmyr Weingartner et al., 2003). Precipitation ranges from anomalies such as intensivefall summer combined with thunderstorms pronounced and snow long-lasting melt as advective well rain- as glacier lake or landslide-dammed per 500 yr-time slicesthe (Carvalho Hasli–Aare and delta, Schulte,by equivalent palaeochannels, 2013). to levees, the The crevasse splaycores bottom floodplain and show of morphology interdistributary how the basins. of layersbeds Sections Lower of and and fluvial Hasli peat gravels, valley, sand horizons isments. and which defined silts are intertongue related with to organic-rich a high water table of wetland environ- According to the instrumental hydrologicalgauging data stations, recorded the since hydrological 1905 regime at isthe defined the as fact Brienzwiler nival-glacial, that taking into approximatelymean account discharge 17 % of of Aare river the is catchment 35 m area is covered by glaciers. The mum discharge of 444 m and mitigation strategiesthese for strategies are natural still part hazards of1876, the have the cultural been landscape lower and Aare developed. settlementhydroelectric pattern. stretch In Since power has AD have some been influenced channelized areas flood and dynamics since due AD to 1932 changes reservoirs in for their retention the Alps, periods(Schaer, of 2003; increased Guyard land-use et have al., been 2007; recorded Ebersbach since et the al., Bronze 2010) Age and various adaptation landforms such as alluvial fans,tennial alluvial climate plains variability. and deltas may be sensitive to intracen- upper Aare river system,limited which by the accumulated slopes a of 12plain the km-long Lower range and Hasli from valley 1 km-wide (Fig. 1.16 1). delta to Sedimentation plain 6.20 rates mmyr of the flood elevation 1578 ma.s.l.), consists ofous carbonate sandstone, rocks marly such shales as and limestone, calcareousthe schist, phyllite. calcare- To Infrahelveticum the (2.4 south % this of arearow is the band limited catchment by of area; sandstone-rich mean flyschof elevation and the 2171 limestones. ma.s.l.) catchment The area; a central mean nar- areanorth elevation of 2171 to ma.s.l.) the south basin belongs (37 the tochlorite; % the para-Mesozoic feldspar-rich Aare gneiss; bedrock massif. and includes From micaschistThe granite and with southern gneiss, rich sericite, catchment in epidoteformed biotite area and by and (28.4 muscovite. basic-ultrabasic % old oflate crystalline the Palaeozoic rocks area; intrusive (amphibolite,slopes mean diorite rocks and and elevation (granite, summit gneiss) 2528 quartz ma.s.l.) areas and steraarhorn. diorite, in is syenite) the Aare forming Massif, the up highest to anlandforms such altitude as of cirques, 4274alluvial m glacier cones, forefields, at discharge moraine the channels, walls, Fin- rockthese scree avalanches, slopes, landforms alluvial debris fans result and and frominterglacial deltas. non-linear adaption Some cycle of threshold (e.g., dynamics rockto avalanches; as low Huggel a frequency et consequence climate al., 2012); changes of others (e.g., the respond Holocene moraines; Hantke, 1980), but some ical proxies of key coresnorthern and fringe for of tracing the sediments basin, to the Helvetic establish Nappe their (31.7 provenance. % The of the catchment area; mean Swiss Alps, is dominatedcrystalline by landscapes alpine in the limestone south,Aare landscapes carved catchment in by is Quaternary the subdivided glaciers. into northÜrbach, The four Gen and 596 major km headwater and by catchments, Gadmen alpine thewhich valleys, Higher additionally and Hasli, is the fed by lower several main tributary valley, basins the (e.g., Lower Alpbach, Hasli Reichenbach). valley, 2 Regional setting The upper Aare basin (46 5 5 15 10 20 25 15 20 25 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3398 3397 ) are among the highest per productive area in 2 − erent sedimentary facies were identified depending on the flood plain ff The most detailed sedimentary records in the Hasli–Aare floodplain, in terms of A total of 16 cores were obtained by percussion coring down to 10 m depth. The AA-10, at a distance ofand 200 m AA-05 from at the delta aAMS shore distance line, radiocarbon of AA-02, datings at 4.5 a km ofLaboratory, distance (Fig. Uppsala peat, of 1). and 1.5 wood km, compared The and to age–depth plant the models remains chronology are analysed of based other at on core the 11 sites Tandem in the study lithological-geochemical and temporal resolution,basins were and retrieved their lateral from transitional interdistributary landforms. In this paper we focus on three key cores: shallow drillings (85 cores). Sediments,scribed organic macromorphologically soil and horizons wood, and plant,collected peat layers mollusc and were fragments classified. de- and Sediment artefactscesses structures, were as facies well and as associatedtion. the geomorphic Furthermore, mineralogy pro- sedimentological data of were selected compiledby flood from the core layers inventories geological were provided database analysed(WWA). of by the thin Bureau sec- of Water Management of the Bern Canton lateral extension of the major units was traced by four cross-sections of 20 m-spaced terrain model. Di and silt deposits areor formed, flood and gaps. organic Therefore, richsurfaces, peat a horizons high layers and water are peat table, and marker during minimum horizons minor sediment that floods contribution. represent stable land morphology, changing environments, and riverdeposits dynamics. Channel are and generally crevasse splay composedand by overbank coarse deposits by sand finerich and and sand gravel, organic-rich and layers levees as silt, by well andmay as sand cause peat interdistributary erosion horizons. layers, basins Particularly and during contain redeposition, shifts, whereasdeposited clay- channels sediments conformably. Thus, in according intradistributary to basins the are resultset from al., the 2008), Lütschine delta alluvial (Schulte the plain sediments Late provide Holocene excellentrecord aggradation geoarchives for aggradation and reconstructing of flood coarse-grained history. flood During layers; larger during floods moderate these floods basins fine sand the Alps. However, the limited spacemostly in to be the found Hasli in valleychine alluvial that delta, fans is no and suitable towns trough for or shoulders. settlement villagesexception In is are of contrast located the to in small the the municipality nearby Hasli–Aareties Lüts- of delta (e.g., Unterbach). floodplain tourism) However, (with present-day are the human notpressure activi- limited during to the traditional 19th lowment and risk of 20th areas, the due century flood to andhydroelectric the plains. the power demographic Furthermore, stations, introduction infrastructures gas of such pipelines,are hydraulic railway as all manage- tracks exposed highways, and to power the flood lines, hazard. Meiringen Air Base 3 Methods The integrated multi-proxy approachin the focuses Lower on Haslifrequencies the valley, were Late the reconstructed main Holocene from alpine geoarchives,sediments flood particularly valley (Sect. dynamics from in 3.1), alluvial the delta geochemicalseries upper plain from records historical Aare (Sect. sources river. and 3.2) Palaeoflood instrumentaltime data series and (Sect. such their 3.3). as Frequencies palaeoflood calibration ofwere proxies, various by investigated historical (Sect. flood data 3.4). records, and climate variability 3.1 Geoarchives from delta flood plains Meso-scale fluvial landforms werevalley mapped by in geomorphological the delta survey1928–1944), flood and IR plain and analysis of SPOT of images, the historical historical Lower maps aerial Hasli and photographs a (AD 2 m-spatial resolution digital capacities. As the resultand of infrastructure, the the development ADthe of 2000 upper grazing, census Aare agriculture, basin. recorded Furthermore, industry, aLower the tourism Hasli population population valley densities of (50–100 of 8190 inhab. the km municipalities inhabitants in in the 5 5 25 20 15 10 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C ◦ er- ff C was punctually ◦ 3399 3400 and NaO could also be measured. Spectrometric 5 O erent excitation of the atoms in the substance in re- 2 ff area (Röhl and Abrams, 2000). The data were acquired content, loss on ignition (LOI) at 950 2 3 O curve. For detailed information on the radiocarbon dating, the reader is re- 18 δ Because the XRF-scan results (counts per area) express the relative variability of For comparison of CaCO To generate environmental proxies from delta plain sediments, the geochemical vari- fluorescence according to the di Digital Spectrum Analyser DAS 1000, andtube an Oxford with Instruments rhodium 50W XTF5011 (Rh)elements X-Ray target Al, material. Si, S, The K,at following Ca, 30 X-ray kV, Ti, tube 0.75 Mn, mA Fe settings and at were 60 10 s; kV, used: and 0.35 Cu mA at and 20 30 kV, s; 0.25 Rb, mA Sr, and Zr, 30 Pb s. and Br measurements were undertaken onestimate pearls the using of a majorThe Philips element major PW contents 2400 elements of spectrometer were 82tional to quantified reference samples samples by collected in a from pearls. calibration the curve split generated cores. bymeasured following 58 Heiri interna- atorganic al. carbon (2001) (TOC) content and was Santisteban analysed systematically et down-core al. by LOI (2004). at In 550 addition, total ability of the core sampleselements was were analysed plotted vs. in lithology, a grain-sizeple and series depth. total of organic Second, steps. carbon elements First, along seriesnature were with of analysed sam- of individual as Ti Ti duringmove ratios, possible because alterations transport in of XRF-scan and the intensities conservative roughness weathering caused by of (Kylander pore volume, the et the split changing al.,ness), core 2011), and surface (counts in so per order on.software area to to Third, decrease explore re- factor the with variability analysis increasingThe of rough- (FA) first the was two geochemical factors computed data were sets with (Schulte extracted the et (rotated al., and STATISTICA 6 2009a). unrotated) from TOC values and the by a Canberra X-PIPS Silicon Drift Detector with 150 eV X-ray resolution, the Canberra provide non-destructive analysis1 of cm split intervals over core a surfaces 1.2 cm collecting down-core data at sponse to bombardment byble percentages incident of energy, element it contents.maximum Therefore, was anomalies calibration was not of carried possible individuallighter out samples to elements by with such obtain conventional as X-ray compara- MgO, fluorescence. P In addition, at 1 cm steps. TOC valuesset of to wood avoid remains alteration were of removed the case-by-case geochemical from proxy. the data To investigate the geochemical variations of2600 years, the alluvial the plain element sediments compositionfluorescence during of the (XRF) the last core samples scanning techniques retrievedconventional XRF (MARUM-University was of (Central analysed Laboratories Bremen) by of and X-ray scanning the by techniques University Serial (AVAATECH of No.2; Barcelona). Canberra The X-PIPS XRF Silicon core Drift Detector) ferred to Table 1 in(2014). the Supplement and to Carvalho and Schulte (2014)3.2 and Carvalho Geochemical flood proxies ent sites. Radiocarbon dating ofshow bulk reversal sediment, of plant ages, remainsbeds and due and charcoal to frequently redeposition sampleagreed processes. contamination with Radiocarbon by the ages reworked sample’swas older stratigraphic were calculated position. organic-rich rejected from The age-depth when chronology modelsibrated they of based ages each on dis- calculated linear core with interpolation(Stuiver sample the et between CALIB the al., Radiocarbon cal- 2014). Calibrationby Calibration program identification of Version of the 7.0 historical geochronologicalsecondly flood model by layers was the and performed correlation metal of firstly thirdly anomalies marker by horizons (from the and the major comparison last geochemical ofcal century), anomalies, possible proxies and and synchronized palaeoclimate trends records. and Forwithin variability example, maximum of age-depth probability models geochemi- were intervals corrected (Magnyof et peaks al., in 2011) our where datathe regular series displacement were observed compared to other climate records such as area (Schulte et al., 2008, 2009a,with b; Carvalho 161 and Schulte, radiocarbon 2013).(when datings, From our we not experience suggest removed) show that consistent radiocarbon and ages reproducible of ages peat that and correlate wood at di 5 5 25 10 15 20 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Rb ratio. / ) because floods AA M Ti peaks were compared / middle and coarse sands). In = Ti ratio calculated in the delta flood plain / Ti ratios were compared with grain-size frac- 3402 3401 / fine sands, M3 = O record (GISP2, Reimer et al., 2004) and Total 18 δ Rb and Sr / Ti, Zr / silty fine sands, M2 raction grain size analyser) and macroscopically and microscopically = ff In the second step, the tributary catchments were included in order to consider the To estimate historical flood intensities between AD 1480 and 2012, in the first step Original flood descriptions were analysed to locate the reported damage geographi- Furthermore, the Zr tributaries and headwaterattributed catchments to were the multiplied floodsin by the in 0.5. main the valley This stretch normally(e.g., higher result of the weight from floods the higher is of lower discharges AD from Hasli–Aare 1762 several ( subcatchments and 1831), while discharges that cause severe damage spatial dimension. In theLower case Hasli of valley the were Aare river, multiplied flood by categories a in factor the of bottom 1, of the whereas flood categories in the flood criteria to localAare physiographic, and socio-economic Lütschine and catchment. demographic settings of the primary and secondary indications werescale defined of for the classifying damage floods andfications according geomorphic and to typologies change the have (Table 1). beenberger, Although proposed 1991; several by flood Pfister, a classi- 1999; large range Sturm of et publications al., (Röthlis- 2001), in the present study we adapted the data by coring along cross-sectionsmation as was described also in obtained Sect. viaAare 3.3. comparisons floodplain In and between addition, the the useful descriptions spatialSwiss of infor- evolution the Inventory of historical the of road Hasli– network Thoroughfares1992). reconstructed (Inventar by the Historischer Verkehrswege der Schweiz, cally, to estimate the floodedage. area Reported geomorphic and processes to such reconstruct asvalidated channel the by migration the type and geomorphological aggradation and were data magnitude obtained of by mapping dam- and the sedimentological the Swiss Federal InstituteAD for 1972–2009. Forest, Singular flood Snow events and wererecords also Landscape of compared Research the to instrumental for IDAWEB precipitation database thestations provided of period Guttannen by since MeteoSwiss AD precipitation 1876charges and data of Meiringen from the since the upper AD 1898. Aarestation Information river located on was dis- 1.4 taken km from from the Lake Brienz, records of since the AD 1905 Brienzwiler (data gauging provided by BUWAL). sediments of the Lower Hasli valley was a moreto sensitive the signal historical than flood index the reconstructed Zr from documentary3.3 sources (Sect. 3.3). Historical flood series and instrumentalFlood data series of thecal upper and Aare regional historical (Hasli monographs, valley)and newspapers, were regional scientific compiled authorities, reports, chronicles, from reports the textual ofmaps, parish historical local sources register) paintings (lo- and and factual photographs)events sources (Pfister, were 1999). (historical These compared reconstructed to flood land episodes provided recorded by Röthlisberger in (1991)the existing for period flood the AD databases period 1496–1995; AD forCivil Gees 1020–1988; Switzer- Engineering (1997) Pfister (1999) for Department the for ofdigital period the flood AD Bern archives 1800–1994; provided Canton) Hählen by for the (2007, the Swiss Flood period and AD Landslide 1600–2005 Damage Database and of tions (laser di analysed coarse-grained flood layers to producesity grain-size levels flood (M1 proxies of threecontrast inten- with the results ofupper Jones River et Severn in al. mid-Wales (2012) (UK), on the the Zr geochemical flood recordsFinally, of the the frequency and magnitude of flood layers and Zr geochemical data matrix (originaling data the and geochronological Ti ratios). modelrecords, The such and as scores reconstructed then were temperature compared plottedgen and precipitation apply- to et curves al., data of 2011), the series Alps the of (Bünt- Greenland palaeoclimate Solar Irradiance (TSI, Steinhilbersition et and al., diagenetic 2009). processeschlorite, To calcite investigate of and the pedological the features provenance, materials, wereand depo- microscopically factor minerals identified analyses in such were thin as section, fractions also of quartz, applied selected to feldspar, samples. conventional XRF data, TOC and grain size 5 5 25 20 15 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 C < 14 3.5 are ≥ erences in height ff 2 are severe and those ≥ 3404 3403 , (1) ) 0.5 · i ) do not necessarily generate significant flooding in the main valley i erent patterns of floodplain dynamics: first, abrupt channel shifts, occa- M ( ff M 1 O anomalies (the GISP 2 record from Greenland; Stuiver et al., 1997), n = i X 18 + δ is the number of flooded tributaries. ) are defined as the sum of both flood categories. Flood event intensities n AA M M C anomalies (Reimer et al., 2004) and reconstructed temperature and precipitation = For example, in AD 1766 the engineer Mirani (1766) measured di The precision and continuity of historical flood data series may change over time. 14 where In particular, informationlimited. on The small data became and moreon medium reliable after River flood the Correction introduction categories of indue before the to AD Swiss AD the Federal 1854, increased Law 1850 information andflood available is episodes, improved in several authors the over (Röthlisberger, press. 1991; the Aset Gees, al., course 1997; for 2011) Pfister, severe note of 1999; and that Wetter catastrophic the theyon are 19th generally society. well century recorded Flood in Switzerland mitigationearly due to as management their the was impact 13th implemented centurycentury (Vischer, in (Wetter 2003) et the and al., more Bernese 2011). frequently Alps since the as 18th3.4 and 19th Spectral analysis of flood andSegments climate of series the geochemical data seriesshow of a cores quasi-cyclic AA-02, variability AA-05 and (Schultevariability, AA-10 et the (Sect. al., data 3.2) 2014). were To processedSchulz explore by the and spectral frequencies Mudelsee, of analysis 2002). this (Schulzflood Frequency and series analyses of Statteger, were 1997; the also uppersuch applied Aare as catchment to (Sect. the 3.1) historical and other palaeoclimate records, of up to 5.4 mFig. between the 1). southern Under andfloods, the this thus northern predisposition changing edges of its thetributary the course basins). river valley Consequently towards (Willi, a can the 1932; new lowest cyclecross-sections break of the parts progressive following through aggradations of shifts begins. were levees the In identified: four valley between during 957 (e.g., and larger interdis- 1251 yrcalAD ( showing two di sionally from one edge of thenel valley aggradation, floor to combined the with opposite; minorproduce and a second, horizontal the dissymmetry displacements. vertical of This chan- thebe pattern valley reinforced floor tends by topography. to In the addition, slow these subsidence dynamics produced may by the compaction of delta sediments. The key-cores retrieved fromdelta the plain Hasli–Aare facies floodplain definedand (Figs. by crevasse 1 sequences of and splay shallow 2) deposits,palustrine gravel show fine-grained coarse-grained channel alluvial sediments, flood beds, organic-rich sandytratigraphical layers data beds levee within an and aggradation overbank model peat deposits, of horizons. the From Hasli–Aare floodplain lithos- is reconstructed, curves from the Alpsodic (Luterbacher signals et in al., unevenly 2002;Walden, spaced 1993) Büntgen was time et performed data al., using1997). 2011). series, the The To a SPECTRUM detect periodograms software harmonic peri- were (Schulz analysiswith and calculated a (Percival Statteger, from rectangular and window, the using Lomb–Scargleconfiguration a detects Fourier significance a level Transform false-alarm of level 0.05the of and 99.6 Siegel a % lambda test for of white (Siegel,cessed 0.4. noise with 1979). This assessment the through The REDFIT red-noise software (Schulz spectra and of Mudelsee, 2002). the records have4 been pro- Results 4.1 Aggradation processes in the floodplain in a tributary ( (e.g., the floods ofriver AD ( 1869 and 1915). Finally, the total flood intensities of the Aare are considered as small and medium-sized, those δ catastrophic. The maximum value of 4.5 was reached in AD 1762. TheM equation is 5 5 25 20 15 10 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C dating; 14 feldspar ratios / ecting the distal area of ff 32 yr cal AD, core AA-21), ect of groundwater dynam- ± ff and frequently contain disperse 3 3405 3406 Ti peaks associated with coarse-grained flood Ti) shows a sensitive variability with maximum Fe ratio, used by several authors as an indica- / / / (Ca 3 80 yrcalAD (core AA-12; 56 Ti and Ca ± / ects which may partially compensate for each other (Pfister, ff Ti, Sr / 172 yr cal BC and 158 ± In the Hasli–Aare floodplain the water table is very close to the surface, ranging Figure 2 shows seven major deposition pulses (units I–VII) of upward thinning se- The catchment lithology is reflected by thin section micromorphology. Eighteen sam- Over the last centuries anthropogenic activity has become a major driver of flood flood layers (Fig. 2). However, the Mn ics on carbonates. Inwhereas core above AA-05 this carbonates depth are CaCO leached below the depth of 213 cm, quences. The aggradation ofrately sandy recorded overbank by deposits Zr duringlayers major (Fig. flooding 2). is Silty accu- ing paludal minor beds, floods, which show high reflect values decreased of sediment K, Ti contribution and dur- CaCO between 1.4 and 2.5 cmthe interpretation in of depth. geochemical Therefore, records. Fora hydromorphic example, positive dynamics Mn correlation, and particularly are Fe in relevant values fine-grainedlattice mostly for layers, when (Tebbens show et they are al., bound 2000). in Minimum the values clay of both elements are recorded in sandy (Supplement; Table 1). The floodby layers historical of sources the (AD youngest 1811 units at3). (unit 36 The cm VII) established depth were chronology and calibrated was AD tested 1851peak by at (AD comparing 44 cm the 1967 depth; interpolated Figs. at agearound 2 of 7 and AD cm the 1970 Pb depth) (Weiss with et al., the 1999). maximum consumption of unleaded gasoline tor of palaeo-redox conditions (Koinigwhere et organic al., decomposition 2003), generates decreases oxygenditions depletion, in and contributing the mobilization to organic of anoxic horizons Mn(II). con- Also important is the e values about 7 % (Fig.geochemical 2). proxy To with avoid maximum inhomogeneous resolution,focuses time on in series samples this and from paper to between the investigate a analysis the depth of of core 217 cm AA-05 and the surface. ples retrieved from flood layers of cores AA-05 and AA-10 show quartz multiple aggradation pulses arelogical intercalated model by 14 of organic the horizons. last The 2600 geochrono- years was established by six AMS radiocarbon ages organic matter and plantat remains. the The top organic of each bedscalm cycle and deposition (at soil environments depths or of horizons 90, even (4–12 to 125, % 188 stable TOC) and conditions 213 without cm) flooding. correspond to relatively 4.2 Sedimentary delta plain records In general, the 10 ma deep marginal core basin AA-05 located reflectsBrienz at low (Fig. the energy 1). southern The deposition basin valleythe environments is floor of Aare protected at northwards upstream distance during by of the a 4.5 landslide last km deposit 3000 from years. which Lake Sand diverted and silt beds deposited during of the river barrier1434 at and the 1865 outlet (Willi,the of 1932; lake Aare Kurz Brienz, delta, and raising (2)local Lerch, it river the detour by 1979), repeated created 1.50–1.95 thus m by levee1932), a the between construction (3) local AD and river the management maintenance correction cooperativethe of as in riverbed the AD well from 1579 Aare as (Willi, the Riverconnected the Aare in reservoirs gorge AD to 1876, to produce channelling themitigation, hydroelectric and river ground power straightening mouth; sealing, since and deforestation,tices AD (4) reforestation, 1933. have the and However, operation opposite flood changing of1999). e land-use several prac- plain dynamics. In the Hasli–Aare catchmenthave a influenced number of the structural floodplain hydraulic measures dynamics in the Lower Hasli valley: (1) the construction the large Kienholz debris flowBalm of landslide AD 1499 of (which AD destroyed 1650,Krummeney the and (until castle to the of a 1860s). Kienholz), the lesser extent the active scree slope southwest of dating; core AA-02 and AA-P1.25) and AD 1762 (historical sources and Aa-P1.12; Fig. 1). Aslides third and mechanism debris of flows574 channel such shift as was the introduced Bitschi by landslide, large dated land- by radiocarbon between 5 5 15 10 20 25 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 0.1) correspond to Ti ratio of core AA- / − 0.5 ( cient carbonate leaching − ffi (7 %) due to the fact that 65 % of the 3 O 0.72; Fig. 2) throughout the entire record. 2 = r 3408 3407 (18 %) and Fe 3 O Ti ratio indicates a significant positive correlation with flood 2 / raction analyses, CaO values up to a maximum of 2 % are related erent facies were detected at core site AA-10, located 200 m from ff ff 0.85 and sand fraction ( (74 %), Al − Ti ratio of core AA-05 (AA-10) samples above / 2 > Ti / The mean chemical composition of the sediments of core AA-02 reflects the domi- Two units of di The 6 m-deep core AA-02, retrieved from a central interdistributary basin located in We stress that thegrain ratios size, and of provenance thesesand of stable in sediments. association elements Zr with provide is quartzof information frequently (Kylander bedrocks of et enriched throughout al., two the in 2011)for Aare kinds: coarse sediment which catchment. supply silt is from At and present the the in highestcause area same many this of time, types heavy the mineral zircon basin is (mean is presentamphibolites altitude: in also 2528 of the ma.s.l.) a crystalline late be- tracer rocks Palaeozoic suchratios, intrusions. as is syenite, The related granite to element and clay Ti, mineral assemblages the and denominator to of phyllosilicates located these in the para- layers (Sr flood layers, thus providing a palaeoflood10 proxy. However, the shows log a Zr reverse patternFig. between 2), depths while of the 156 log and 188 Sr cm (1460–1350 calyrBP; that the log Zr 4.3 Geochemical palaeoflood proxies The youngest sediments (217–0 cmportunity to depth) study at flood the dynamicsanisms key from at alluvial site a plain AA-05 high sediments provide resolution.five and organic a Seven their soil clusters related good horizons of mech- (TOC op- 4–11 coarse-grained %) flood and silt-rich layers still intertongue water deposits. Figure 3 shows the delta plain deposits ofogy the of upper AA-10 unit, was which basedfine-grained on cover still the the water last correlation deposits 700 of of years.century, beds core such The with as AA-05. chronol- characteristic the In flood Pb addition, peak layersmay the at and be metal 9 cm peaks associated depth of with and the pre-WW Znfied. 20th peak I Radiocarbon at zinc ages 20 cm tin on depth production;show charcoal (the reversals Weiss latter and of peak et plant age al., fragments due 1999)the to were distal were redeposition rejected delta identi- processes floodplain because of environment. they the charcoal After geochemical correction and of plant variability the remains (factor geochronologicalwith in 1 model, the scores) variations of of core AA-10 AA-05 shows (Fig. a 3; Sect. very 4.3). close correlation catchment consists of crystallinethan bedrock 30 of % the ofriver Aare the Massif system, Aare (Fig. Ca 1). counts catchmenting Although are area to more very the contributes X-ray low carbonate-richto di in hornblende sediments the and to total not databeds the to series (except carbonates. for of The the core absence lower AA-02. of gravel Accord- deposits) carbonates suggests: in (a) the e fine-grained nance of SiO Lake Brienz. The lowercoarse unit sand (between and fine depths gravelper of which unit 1.80 (0–1.80 were m and deposited depth) shows on 12.00 sandy m) the floodplain consists delta deposits. In front, of the whereas clean paper the we refer up- only to 220 cm, multiple pulses ofsedimentation. overbank The deposition upper show a unitup general (50 to trend 45 to % of 220 total upward cm organicof fining carbon. depth) the The contains floodplain presence lasted four of minerotrophicalluvial more peat fens floodplain than horizons in sedimentation half the with started a central again. area millennium, from 1450 to 1000 calyrBP, until by acidic water in peatas wetland a environments, source and of (b) fine-grained the materials dominance (the of metamorphic phyllosilicates rocks of the Aare massif). the axis of thejor aggradation Lower pulses Hasli over valleyriver the were floor last drilled 2600 from 2 years. km 800 Coarse toceased from abruptly, channel 650 probably cm the deposits due depth. to of The lake channel aggradation theposition abandonment, shore, of and of Aare the records continued organic channel through and nine facies the then silty de- the ma- material influence of from the palustral Aare environments. river After is 2220 again calyrBP, more noticeable. Between the depths of 470 and of grains (30–1500 µm) rangingfeldspar from contribution from 0.4 the to plutonicment, 0.7. bedrock particularly Low in during the ratios cooler highest point climate terrain to pulses of the (Sect. the dominance Aare 5.1). catch- of 5 5 25 20 15 10 20 15 25 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O 2 O (plagio- 2 3410 3409 -MgO (biotite, e.g., in gneiss), Sr-Na 3 O ers from that of the other core sites: the first factor 2 ff O (K-feldspars), Fe 2 With regard to core AA-02, factor analyses were applied to three data sets. First, the To conclude, the analysis of the geochemical records of the cores AA-05, AA-10 and Factor analysis was also applied to 27 calibration samples in which grain size data Factor analysis (FA) is a powerful tool for inferring palaeoenvironmental processes These findings coincide with the results of core AA-10. The 2-D-plot (not shown) distribution of variables of scanned samples(Fig. retrieved from 4c). 0–551 The cm depth order was of studied the factors di rocks) and, finally, a groupand defined siliciclasts). The by loading theexcept of elements for the Zr, Sr, sand indicating Sr, perhaps fraction (Al) acomposition is and lesser of the Si influence samples. opposite of (plutonic Ca the of rocks is sand all related fraction other on to variables, the hornblende chemical and feldspars. AA-02 provides evidence thatinfluenced the by: (1) chemical grain composition size,(organic of (2) material, the the lithology leaching floodplain of of depositsof the carbonates source provenance is and were area, and detected redox (3) bybedrock, processes). soil FA: The the the formation following southern central areas catchmentclearly) area area the a comprised northern plutonic predominance area presented of carbonate-rich metamorphic bedrock. rocks, and (though less of AA-02 corresponds to factorof 2 variance, of corresponding AA-05, to and F2of vice K, of versa. Ti, AA-05) Factor Al, is 1 Fe,of defined of Rb variance, by AA-02 corresponding and the to (52.9 Mn strong % F1 andmetals negative of the on loadings AA-05) positive the shows loading opposite Zr of side. andshowed Second, TOC, Sr the whereas FA on typical of factor one element 26 side 2 calibration distributioncontent and (21.3 samples of % percentages: TOC (conventional the and Fe, XRF) Hasli–Aare Al, delta Tithe floodplain and according silt Mn to fraction; (phyllosilicates, metamorphic Zrfinally rocks) a (quartz related group to diorite-syenite, of Sr, granites)these Na related and outcomes Si to (plagioclase, are the quartzgrain-size supported diorite) sand fractions with fraction of by weak approximately and, loadings. additional 300 Finally, (Fig. FA samples 4d). collected computation from of 251 to XRF-scanning 551 cm and depth and conventional XRF databy were an obtained element (Fig. distribution 4b). veryspite The similar the to first reversals that two of of factorsthe factors the are F1 scanned FA and defined of samples, F2, scanned and the XRF show samples. groups a De- of noticeable the relation variables to are grain-size: equivalent Zr, to Sr and Na with carbonates and plagioclase),The while second the factor (F2; loadings 22.8 of %als of Si (Pb, total and variance) Zn, Ca demonstrates Cu) positive areAl, loadings associated not and of with met- K, significant. organic associated with material siliciclastic (TOC) rocks. and negative loadings of Si, are related to the sandsuggest fraction, that phyllosilicates there to is silt,(Schulte a and lithological et metals control al., and of TOC 2009a)Pb-TOC the to because (metal-organic clay. chemical We several complexes), composition Zn-Clay variables of (enrichment aresurfaces), the due Rb-K grouped to samples in increased characteristic adsorption clase pairs: e.g., in quartzplutonic diorite; area). a less close relation) and Zr-Sand (heavyof minerals loadings in shows the thethe following clay groups fraction of (soil variables: formation), phyllosilicates metals related and to TOC the associated silt fraction with (metamorphic from geochemical variables ofAA-05 a (Fig. sediment 4a). record, asproperties Factor exemplified 1 of by the (F1) the samples explainspositive data measured loading 47.9 of % by of core XRF Fe, of Ti, coreand the Rb, K-feldspars scanning. K, variability in It Al gneiss of is and andZr the defined Mn (associated other by (phyllosilicate with geochemical metamorphic heavy components a rocks), minerals such strong a like as zircon strong biotite and negative also loading with of quartz) and Sr (associated Mesozoic metamorphic rocks of the2171 central ma.s.l.). area of Finally, the Sr Aare valuesreported catchment are (mean by associated altitude: Kylander et with al. both (2011) carbonates and and illustrated silicates, in as Fig. 4. 5 5 25 20 10 15 15 20 25 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O val- 18 δ ect on the ff peaks (Fig. 2) O values may 3 18 δ Ti and CaCO / C production rate (Stuiver et al., 14 Ti peaks does not systematically coin- / 3411 3412 cult to evaluate in all cases whether a flood layer corresponds ffi Ti ratios and with a total of 26 coarse-grained flood layers, forming seven / The figure (Fig. 3) illustrates a significant correlation between the clusters of flood lay- To study the flood dynamics prior to periods of persistent human impact on land- Although trends in geochemical proxies appear to show a close correlation with the The correlation between cores AA-10 and AA-05 and also with the historical data delta lobes on the other.tween The AD lowering 1852 of and the outlet 1862 of (Willi, Lake 1932) Brienz may by have 3.5 decreased feet the (1 blocking m) e be- ers detected in core AA-05(Sect. and 4.5). the Aare However, flood the episodes magnitude recorded of by the historical sources Zr the visual correlation between the sedimentary proxies of core AA-2 and the scape, as shown bypercentages; palynological Schulte data et al., (falls 2009a), in wewhich focused arboreal provides our pollen high analysis particularly resolution and on records mesic core from AA-02 tree 2600 pollen to 1600 calyrBP. Figure 5 illustrates pointing to increasedbedrock discharge (lower contribution Aare fromcurred catchment, catchment around mean 1390, areas 1480, altitude: with 1660, 1578 1700 ma.s.l.) calcareous and 1760 during cal yr floods AD. that oc- cide with the historical flood intensity,are for the defined following by reasons: higher firstly, some carbonateare flood contribution layers changes and in decreased the Zr distance values;area; from secondly, and there the thirdly, main historical channel flood and series in may the also extension include of a(Fig. the range 3) flooded of uncertainties. provides argumentsflood plain. for However, the the amplitude validity ofcore factor of AA-10 1 are and flood the lower reconstruction total thanrecords, number in in of due core the 13 AA-05, to flood indicating Hasli–Aare the layers a in influenceof lower of suspended sensitivity flooding of load by the during Lake floodplain to the Brienz the on AD change one 1390 in hand and the (e.g., 1762 distance deposition flood from the episodes: channel see as Sect. a 4.5) consequence and of displacement of river drainage caused by highrection lake Project levels. Since in the AD termination 1875,have of geochemical been the and Hasli–Aare grain noticeably Cor- size masked floodby because proxies structural sedimentation of flood both processes mitigation core have (Sect. sites 4.5). been reduced 4.4 Correlation and periodicities When the scores ofpulses inside the the first overbank deposits factortion are are environments. detected, For which plotted example, indicate aggradational against changing pulsesare sedimenta- depth, in characterized core multiple over AA-05 the aggradational (0–213 cm(metamorphic last depth) rocks) 700 years and by the thegranite, decline increase quartz in in diorite elements the andshown such phyllosilicate by syenite as content Zr (intrusive negative and rocks scorespeaks Sr of at of Zr associated 2528 factor ma.s.l. with 1episodes: mean (Fig. 1250–1350, altitude) 3). around as 1390, These1811–1851 calyrAD. 1420–1480, negative 1550–1620, Eight scores of 1650–1720, coincide these flood 1762 with layers and show Ca climate proxy, it is di ues of the GISP2 recorda of time the Greenland slice Ice of sheet(XRF-scanned (Fig. samples) 1000 5a; years. defined Reimer Figure by et(positive siliciclasts 5b al., scores). 2004) (negative represents over scores) Additionally, the Fig. andples variability organic 5c and of content grain shows size scores scores fractions),sand of of where fraction, factor whereas negative factor positive scores 1 2 scores correspondFig. are (XRF-scanned to associated 4d). sam- Si, with The Sr, TOC Ca, and curvescontent metals Zr show and (Sect. and 4.3, elements a associated veryrelates with similar with plutonic pattern, a rocks cooler from suggestingcorrelate climate the that with in highest milder the Greenland catchment climate higher whereas cor- pulses. silicate soil formation and lesser flooding to precise climatecalibration pulses (e.g., (minima for or thehistorical peaks). sources period The (before 450–700 reason 700 calyrBP) calyrBP).there for may or this Furthermore, be total the is time question lack the lags arises of inadequate between of any the whether two calibration data by series: for example, record delays from 0 to 40 years with relative to the 1997; Versteegh, 2005). 5 5 15 10 20 25 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2) in the Hasli– ≥ M 2) were recorded after AD 3.5), three of which reached M < 211 yr cycle; Versteegh, 2005) in M < ∼ ≤ 60 years were not considered due to the 2 were obtained, because minor damage < 3.5) recorded not only extraordinary flooding 3414 3413 ≥ M < M 105 yr and the Suess cycles ( ∼ 3.5), and eleven events as severe floods (2 ≥ 81 yr cycle), the From AD 1480 to 2012, fifteen severe and catastrophic floods ( Because of the quasi-cyclic pattern of the geochemical delta plain proxies and the According to the results (Table 2) the sedimentary record of core AA-2 shows peri- M ∼ was not recorded innine written minor sources. In floods contrast betweenartefact to AD which this 1855 reflects lack and a ofing AD turning flood hydrological 1875 point data, hazards. can Firstly, in a after be the cluster thelocal interpreted of destructive human-environmental residents events interaction were partially of more regard- AD as sensitivelikely 1831 an to to and hydrological AD report hazards; 1851, minor secondly, they orauthorities were medium to more flood fund damage in theily order creation eroded to the of force infrastructure the aits cantonal of solid and construction the river state from Hasli–Aare embankment; AD Correctionmeasured and Project 1867 (AD during thirdly, to 1875) floods by the 1876 engineers eas- period (Willi, (Hählen, of 1932) 2007). and were therefore reported and 1855. Before AD 1855 no records of Aare were caused bythunderstorm three events rainfall and episodes, oneinformation). three rainfall All rainfall-snowmelt catastrophic episode episodes, floods with three ( thunderstorm (five events without magnitude of the uncertainty intervalstion in was fluvial not deposition possible. environments when calibra- odicities around 60, 80,With 100 and regard 205 to years the forthe last the existence 700 period of years, from three the 2600 cycles:riodicities spectral 80, to of analysis 96 1600 60, calyrBP. of and 86, 196 the years.periodicities 102 AA-05 Factor and obtained 1 record 184 from of suggests years. core the All1997), AA-10 GISP2 the the shows cycles record Total pe- Solar obtained (69, Irradiance are (75, 81,and 86, very 105 the 105, similar North and 129 to and Atlantic 208 the yrs; 207drochronological Oscillation yrs; Stuiver Steinhilber (65, series et et 80 provide al., al., and 2009) vals cycles 100 yrs; of of Luterbacher 73, reconstructed et 130 al., and( spring 2002). 200 yrs precipitation Den- (Büntgen at et inter- al., 2011). The appearance of the Gleissberg in the Lower Hasliments valley and/or floor tributaries. but The also extensive1831 impact damage floods of in in the one the ADtial or Hasli–Aare 1342–1343, distribution more 1480, catchment of 1762 coincides headwater flood and with subcatch- damagethese data the in indicate Swiss greater episodes catchments of volume long (Röthlisberger, andquence lasting 1991). of spa- rainfall Moreover, higher or temperatures rainfall plus and snowmelt snowlines.event as The in a cause the conse- of Hasli the valley is extraordinarymay not AD known, 1551 suggest but local the lack heavy ofunlikely precipitation. damage because in A other from scenario Swiss the catchments of historical a and single instrumental glacier data outburst of flood the Lütschine is catchment the data series analysedconsidered provides as evidence a that major the driver of influence floods of in solar the4.5 forcing Aare catchment. can be Historical flood series The reconstruction of the Hasli–Aarethe floods period yield a 1480–2012 total (Fig.ing of 7), 35 to flood with the damage classification flood events(94 for of %) intensities occurred Table ranging 1 during from the and extended 0.5 Eq. summer to (1). period (JJAS). Thirty-three 4.5 This of accord- temporal the distribution 35 reported events intensity level 3. Finally, 21 small and medium floods ( is consistent with the findingsflood of data Weingartner from et 85 al. Alpine1342–1343, (2003), catchments 1480, who in 1551, analysed Switzerland. 1762 instrumental Five( and extraordinary 1831) episodes (Fig. (AD 7) were defined as catastrophic floods possible correlation with the Greenlandmer Ice temperature record (Fig. and 5) springanalyses and precipitation the were of reconstructed performed. sum- the Thefrom Alps harmonic AA-05, (Büntgen analysis F1 et (Fig. scores al., 6a)composite from 2011), was palaeoflood AA-10, spectral applied F1 record to andseries (AA-05 F1 F2 considering and scores scores noise. AA-02) from The(Fig. AA-02 to valid and, 6a detect signals finally, and detected periodicities to b). were the in Peaks above the of the time return Siegel test intervals level 5 5 10 15 10 15 20 20 25 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3; the area was de- ≥ (a conservative estimate) M 1 − s 3 3416 3415 did not produce any damage or flooding in the Lower Hasli 1 − s 3 Ti) peaks in Core AA-05 (Fig. 3b) and to a lesser extent also in core AA- / 1 disappeared completely between AD 1876 and 1976. First, a flood gap in Swiss ≥ The flood dynamics in the Hasli valley changed significantly after AD 1875, as illus- The magnitude of the damage and extent of flooding in the Hasli valley is illustrated An important issue in the research undertaken is the question of whether historical hydrological time series isNaef reported (2010) by and Röthlisberger Stuckito (1991), et long-term al. Schmocker–Fackel and (2012). summer PfisterSchulte precipitation (1999) (2014) minima attributed stress the the betweenin decrease lack Switzerland AD of of as 1935 floods a extremelantic consequence and weather of Oscillation. conditions 1975. the from Second, predominance Peña AD accordingand of and 1944 to reservoirs negative substantially Summer to Gees reduced North 1972 (1997), smallerHasli At- river and valley medium regulation, several floods embankments actions aftertem AD contributed (Sect. 1854. to In 4.1): the the loweringriverbed flood (AD of 1875), mitigation the the in lake commissioningsince the level of AD in interconnected Aare 1932, reservoirs and (AD river and moreexample, 1862), sys- power recently in the plants the AD channelling construction 1875, of of thea retention year discharge the basins the of Aare (AD Hasli–Aare 351 2013). m correctionvalley, whereas For was one year completed, before, a in AD floodin 1874, the with bridges new were embankment destroyed were anda eroded, two breaches even foot though lower the than flood in level AD of 1875 the (Hählen, Aare 2007). river4.6 was Estimations of historical flood discharges Determining the historical flood dischargesis a that challenging defined task the and damage inhistorical this threshold data paper (Fig. and we 7) present the only dischargeof some the measurements rough embankment by estimates. in From engineers AD the during 1875tion (Hählen, the of 2007) the construction we Aare can Correction assume in that AD before 1875 the the termina- level of 351 m trated by Figs. 7M and 8. For climatic and anthropogenic reasons, floods of intensities area of fine materialfrom deposition the SPOT and satellite delimitation (30AD of August 2005 2005; the flood, Swisstopo) and flooding from images, can oblique taken be aerial six photographs days easily taken after traced on the the day after the flood. last half millennium, no coarse-grained flooda layer minor was change detected was in observed coreexplained AA-10 in and by the only geochemistry the (factor rise 1). ofdelta, This Lake meaning contradiction Brienz that can only be (Willi, suspended 1932) fine and material flooding was of deposited the at the distal AA-10 area site. of The the by the following examples.floods According destroyed to entire the villages: historicalin Bürglen, sources, AD Tschingeln, the Hinterluchena 1551 most and (Aare); catastrophic Meiringen Niederhufen or in parts 1342–1343, of 1762Lower villages and Hasli as 1851 valley occurred (Alpbach). floor in Flooding corresponded Balm of to in larger flood AD areas 1551 intensities of (Aare) the and 10 (Fig. 3calthough and the d), AD 1762 where flood the is influence the largest of event recorded Lake in Brienz the is Hasli valley noticeable. during For the example, we can assume thatspreading flood approximately 20 crests km. did not produce severe damage in the deltas after the 15 severe andHasli–Aare catastrophic Correction events in which ADand occurred 1875, log(Zr before are the also termination detected of by the coarse-grained flood layers floods are reproducible by the proxy data from sediment records. No fewer than 13 of scribed as a “continuous(AD lake” 1762) (AD or 1851), “only1979; trees where and “boats Mätzener; stables crossed 1984). were the visible”floodplain Many highest (1867; morphology, of Willi, particularly fences” 1932; these shifts Kurz1831), of floods and and the Lerch; introduced Aare caused important mainplain massive channels dynamics changes aggradation (Fig. (AD 1) in of 1499, were gravel,1766, the 1762, documented Wyss stones by historical in and maps 1813 published boulders. andSchulte, by Dufour Both 2014). Mirani in in Mass flood AD 1876 destruction and1342–1343, of by 1499, houses geological 1551, cross-sections and 1762 (Llorca lossplease and and for of 1831 assistance farmland, generated and as subsequent famine, reorganization. occurred abandonment, migration, in AD 5 5 10 15 20 25 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 1 − s 3 0). The ). These (Hählen, > σ 1 i − M s 3 0 and = AA 1; dry autumn; Richli and M = 0.5: see Eq. (1) – when the AA + M 2 ected the Higher Hasli–Aare sub- = ff M 1, then 3418 3417 = i 1. Since AD 1875, flooding of this magnitude dis- M ≥ AA M 2 and = ; Siegenthaler and Sturm, 1991) were probably deposited by AA σ M 1). For example, during the flood of 10 October 2011 (367 m = AA cult to homogenize the flood intensities series before and after river cor- M ( corresponded to an intensity of 2.5, but if it had occurred before AD 1875 it ffi 1 1 − − s s Ti) values. Organic beds just below and above the coarse-grained overbank de- 3 3 / 1). However, since AD 1932 several connected reservoirs have been in operation 2 and as a result may have been considered as severe events. Interestingly, dur- = ≥ However, geoarchaeological data recorded from excavations of the Sankt Michael There are no written reports of the AD 1342 and/or 1343 event in the Hasli Val- Under the present river configuration, the AD 2005 event with a discharge of M appeared from the data series untilcatchments AD was 1977, any and damage only noted, in and tributaries then and only headwater low-scale sub- ( the water slightly overtopped( levees at Unterbachfor and hydroelectric power caused generation. The small floodsflood that pounded of occurred lakes AD during the 1999) spring andof (e.g., the early the Higher summer Hasli were valley because retainedproduction the for during reservoirs the recorded the most lower winter levels part months. due(the to Through in reservoir electricity late the level is summer, headwater retention high, due capacityas to is it snowmelt), lower but did it in can still AD contribute to 2005 flood ( reduction new threshold of flooding in370 the m Lower Hasli is located approximately between 360 and rection and reservoir construction, at least in the data series analysed. level was low due to inspection work) and in AD 2011 ( 2007) which may have markedclude, the the possible changing magnitude configuration ofmakes of catastrophic it the floods. di mitigation To con- structures and retention capacities ing the 1860s engineers originally planned a channel capacity of 510 m Andres, 2012). Flood levels,profiles reconstructed downstream from of lichenometric the dating Räterichsbodenseenot at included Dam three in during this sample summer paper), ADcatchment indicate after 2014 that AD (results floods 1932, still but a thatin the AD flood 1922, levels the of year known of floods the are last much lower major than flood444 m before the construction ofmight the have reservoirs. reached intensity 3trophic. or Likewise, 3.5, various in eventsM which of case intensity it 1 would and have 1.5 qualified may as correspond catas- to intensities several construction and restoration phases (phasesto I to flood XIII) of events which (e.g., somewas are AD damaged related 1733 twice and by destructive 1762). floods According just to before Gutscher AD (2008) 1351 the the church date engraved on church in the village of Meiringen, located on the alluvial fan of the Alpbach, indicate 4.7 Evidence of the AD 1342The and/or catastrophic 1343 flood flood episodes waveas of the “Magdalena AD flood”, 1342 isrope and/or described during as 1343, the the last cited millennium. outstanding in The floodcontroversially number discussed episode the of in in pulses, Bork German Central their and exact literature Eu- Bork datesKiss (1987), and Röthlisberger (2009), drivers (1991), Wetter are Glaser et (2001), al.central (2011), and Zbinden northern (2011) Switzerland and historical Hergetanalysed information et (Pfister about al. this (2015). and flood Whereas1999; Hächler, wave in Wetter has 1991; et been al., Siegenthaler 2011),bidite and beds little recorded is Sturm, in known the 1991; about sediments1270–1420 calyrBP its of Röthlisberger, Lake impact Urner (2 in and western dated between Switzerland. 990–1250 Tur- and channels) influence the depositionthat environment the and nature flood of bedsat sediments, identified 197–189 it cm in is core show striking log(Zr AA-05 the at highest 211–200 cm scoresposits depth of are and Factor dated in 1, by coreages high radiocarbon AA-10 are to sand quite 1179–1269 contentferent consistent, and (85 catastrophic %) but 1279–1394 flood calyrBP they and events, do such(Röthlisberger, (2 1991). as not the allow AD a 1275 priori or 1342 to and/or distinguish 1343 between episodes dif- the AD 1343 flood in the River Reuss. ley, but interesting evidence candata. be Although inferred from changing sedimentary distances and between geoarchaeological source and deposit (e.g., shifts of river produced damage of intensity 5 5 25 10 15 20 10 25 15 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | of materials into the Aare river sys- 3 3420 3419 ect the area of erodible metamorphic rocks and ff of sand, gravel and stones over a distance of 7 km to the basin 3 more (Hählen, 2010; Huggel et al., 2012). After the sediment input 3 by the Spreitlaui creek on 12 August 2010, within a few days the Aare 3 The increased input of phyllosilicates during warmer summers can be attributed To conclude, the sedimentary data of the flood plain and the geoarchaeological find- shallow soils (Lithosols andage Regosols) altitude with of low 2171 ma.s.l. waterstrated (from retention most 619 capacities clearly to in at 4076 the ma.s.l.) andebris Rotlaui aver- and and flows their Spreitlaui on impact tributaries. the can In Rotlauitem, be the fan AD demon- and yielded 2005 500 flood, since 000 large m yielded then 600 pulses 000 m inof AD 100 2009, 000 m 2010 and 2011 on the Spreitlaui fan have transferred 20 000 m of Innertkirchen (intermediate storage; Hählen, 2010). The absence of any increased permafrost is locatedsnowmelt processes at (rainfall on snow approximatelyof cover and warm 2600–2900 ma.s.l.), frozen air soil, masses, snowmelt rainfall, snowfallconnected due on to dynamics and unfrozen the particularly soil) entry repeated during a late spring and summer. These to a variety of mechanisms such as permafrost degradation (limit of continuous records of the lastadequate 700 resolution years (Sect. (Sect. 5.1),secondly 4.3) on in and the which is possibility palaeoclimate of(Sect. supported extending 5.2). information by this obtains palaeoflood historical model data to (Sect. the past 4.5),5.1 2600 years and Palaeofloods and climate variability ofFigure the 8 last illustrates 700 years the quasisent cyclic silty variability beds of rich Factor in 1soil phyllosilicates scores, formation and where during organic maxima phases matter. repre- This ofment, and facies minor the is flooding deposition related or of to fine floodmetamorphic in grained gaps, rocks. situ crystalline soil According material to erosion particularly Figs. in fromhigh 8 areas the Total and with catch- Solar 9 phases Irradiancetures of (Steinhilber smaller (JJA) et floods in correlate al., the with density 2009) European chronologies and Alps (Büntgen as to et reconstructed al., higher 2011). from summer recent tempera- and historic larch ring the 1342–1343 flood episodesJuly occurred 1342, July-August-September very 1343; likely Hergetthe during et episodes al., the of 2015; summer February Kiss and months et November (e.g., al., 1342 2015) should and be so excluded. 5 Discussion The spectral analysisof conducted the (Sect. variability 4.4) ofclimatic provides sedimentary records floodplain evidence proxies of that are the theagreement similar with Alps, frequencies to the Europe solar the cycles. and cycles Moreover,ical the of the proxies synchronous palaeo- of evolution North of core the Atlantic AA-02fact geochem- that and, and floods the furthermore, in Greenland the are Icefactors Hasli–Aare in and/or Record are by influenced GISP2 not the (Fig. just Northern 5)anisms by Hemisphere points and local climate. to drivers factors To but of the investigate by catchment the regional dynamics, possible the mech- discussion focuses firstly on the flood ings of the Sankt Michaellikely church left suggest their that mark thespecific AD on flood 1342–1343 the episodes flood Hasli episodes duringAccording valley, very AD but to 1342 it the and is flood 1343 not pattern possible in reconstructed to Central by assign Europe time the or events series Switzerland. to from AD 1480 to 2012, the church bell,the but northern no wall particularrebuilt (phase flood (phase VI event VII). During according wasdebris a to named. second up Gutscher, The flood, to 2008) first massivedue a aggradation which flood either filled height was to damaged the of the subsequently churchConsequently, 3.5 volume the with m. new of church In material floor this or wasGutscher built to (2008) case right argues the on the that short the the ancientthe flood recurrence two archaeological sediments church floods findings interval (Phase showed occurred was of VIII). that within the the not aafter church events. walls very the excavated, were short not first time, plastered event; with because Oberland this mortar during would the have 14th been century. highly unusual for a church in the Bernese 5 5 20 25 15 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | dur- 198). ff cients = ffi n on slopes. For ff 0.47 between Zr and TOC ( − = r 3421 3422 and Sr values) are recorded. These elements 3 Ti ratios were obtained in beds dominated by coarse- / Ti and Ca / ect on the Rhine, Reuss and Linth basins. The flood was caused ff Ti, Si / Ti peaks are not recorded during warmer climate pulses. We suggest that / 0.58 between Si and TOC and − ect of permafrost degradation on erosional processes in the plutonic bedrock ff = r Nevertheless, the aggradation of the palaeoflood clusters (1250–1350, 1420–1490, Cooler climate trends promote glacier advance and more extensive snow cover. This The possible correlations of periods of low flood frequencies with the regional cli- Against this background, it is interesting that during the warmer climate pulses berger (1991) and validated laterevent by was Schmocker-Fackel and the Naef outstanding (2010),had the flood an AD episode intensive 1762 e in Switzerland during recent centuries and climate (Fig. 8).incide Furthermore, with the the 1550–1620 flood-richNaef and periods (2010), Glur in 1811–1851 calyrAD et Switzerland al.the identified (2013) clusters highest and by Zr co- Peña Schmocker–Fackel et and al.grained (2014). flood layers Minimum (Figs. scores 2 ofof and factor 3). 1 The and correlation matrix shows negative coe 1550–1620, 1650–1720 and 1811–1867 calyrAD)riods with occurred cooler predominantly during summer2012), pe- temperatures reduced (Büntgen solar et irradiance,sulphate al., clusters from 2006, of major 2011; increased volcanic eruptions Trachsel Northern et (Gao Hemisphere al., et aerosol al., 2008) and phases of drier spring by the combination of four1984; days Röthlisberger, of 1991). rainfall, high temperatures and snowmelt (Mätzener reflect sediment yield from limestonefected the areas, lower thus catchment indicating (1578 ma.s.l. rainfallcase events mean in altitude) that of the also the AD af- Hasli–Aare. This 1762Lower was event, Hasli the the valley largest (Sect. floodbedrock ever 4.5). was recorded The demonstrated by by lateral historical the contribution sourcesflood tremendous in from which description the tributaries caused of massive the with aggradation catastrophicAccording limestone in Alpbach to the the historical village flood of analysis Meiringen of all (Mätzener, 1984). Swiss catchments conducted by Röthlis- greater water storage in turn produces higher base discharges and surface runo precipitation anomalies (Büntgen et al., 2011)1660 from and 1350 from to 1720 1410, 1500 tomers to 1810 produced 1560, calyrAD. around increased discharges The during combinationwarm spring of and high wet early springs summer, summer, and the whereas warmoccur critical during sum- during season this for time), large lessthe flood stored Hasli–Aare events water (92 indicate % volume that is inwarmer available. floods climate the The pulses triggered Hasli–Aare historical or by data intermediateand thunderstorms from climate Weingartner (Figs. correspond 7 et mostly and al. 8).produce to However, severe (2003) Pfister flooding (1999) stressed in mid- that and local large-size or catchments. shortaround thunderstorms 1390, only 1660 rarely andbonate contribution 1762 cal (high yr Ca, AD, CaCO coarse-grained beds with a noticeable car- According to these relations,coarse-grained overbank floods beds of with resistant high siliciclasts(e.g., (e.g., flow zircon) quartz) velocities and eroded heavy deposited from minerals mean medium the altitude; Figs. highest and 1 catchment and 8). with plutonic bedrock (2528 ma.s.l. ing summer months (Stuckiclimatic et snowlines al., and 2012). glacier Astible advances, regards it to the is melting spatial important processes significanceincreases to of (e.g., associated note lower caused with that by the rainfalland Foehns) area may episodes can shift suscep- and grow to the substantially abruptand high in temperature snow summer mountain patches (flood) topographies through season.and Moreover, the saturated the summer soils outlast of favours in snow the adjacent cover existence terrain, of thus increasing impermeable surface areas run o mate variability arephyllosilicates shown (maximum in scores) correlate Fig. with 8. positive Periods late spring of and reduced early summer flooding and deposition of discharge of the Aareupper during slope, the this fluvial period systemF1 indicates and or the the Zr delta high floodplains.the connectivity However, e between negative scores the of area of the Aare(2528 ma.s.l.) catchment is has been less locatedthe important above present the because warmer permafrost more climate limit (Institut than (2600–2900 ma.s.l.) für half Kartographie, during of 2004). this domain 5 5 10 15 25 15 20 25 10 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 ect ≥ ect. ff ff M C line. This ◦ cult to assess ffi ects of the structural ff 3424 3423 erent kinds of anthropogenic activity may have had a compensatory e ff Comparison between the historical flood intensities (Fig. 7) and F1 score (Fig. 8) In addition, atmospheric dynamics during the winter season may also have a delayed Palaeofloods in the Upper Engadine (eastern Switzerland) from 1177 to The influence of land-use on flood discharges and sediment yield is di From the historical data (this paper), the study of flood damage in Switzerland over from the Lower Haslidata; valley Peña et and al., the 2014) SNAO from AD index 1700 (annual to values 2000 show and the 11 following yr relation: floods smoothed glacier dynamics (Stewart etbetween al., increased 2011). floods Wirth in etdeposits, the al. and Southern (2013) overall Alps, underline annual reconstructedAge, the and due by coincidence to decadal flood a negative layers southerly NAO in position phases of lake the during Atlantic the Storm Little tracks. Ice influence on summer flood frequencies, especially in terms of snow accumulation and Level Pressure (SLP)caused increased over advection of western anomalous2000 calyrAD. humid Europe south and westerlies between the 1950 and western Mediterranean that 2000 calyrAD were reconstructedcording by to Stewart their et results, al. floods (2011) may from be lake related sediments. to Ac- strong negative anomalies of Sea in the Aare occurredclearly displayed mostly by the during AD positive 17491987 flood trends and and 2005). of by In the the SNAO modern casethe phases. of floods episodes the since This correlate severe AD AD to pattern 1977 1703, short (1977, dominated 1707, is positive 1811, by SNAO 1831 negative and pulses SNAO. 1851 following This floods, of years combination snowmelt or points (e.g., even to decades together the withduring importance extraordinary short of heavy warm the rainfall; episodes Weingartner e cover within et and glaciers. al., cool Only 2003) climate the periods ADpulses 1733 dominated characterized and by by cool-moist 1867 larger air floods masses snow occurredThe transferred during AD by negative North SNAO 1762 Atlantic flood, frontpattern systems. the defined largest by eventSNAO a recorded mean negative in values, annual the probablymelt. SNAO Hasli This because index is valley, supported shows of within by a the theepisode a historical (Mätzener, singular relevance longer sources 1984; that of Röthlisberger, pulse report 1991). drivers an of exceptional other 4 positive day than rainfall snow example, the magnitude ofbelieved the to most be recent related major totended Aare the snow floods increased cover (AD (cool-moist melting winters; 1831 processes Pfister,trend of and 1999) towards advanced 1851) as higher glacier a is summer and consequence temperatures of ex- and the marked a higher altitude of the 0 cooler climate trends during thesnowmelt Little triggered Ice by Age North reflected Atlantic importantand dynamics. rainfall catastrophic With episodes floods regard with to in the Switzerlandysed frequency since the of influence AD severe of 1800, the Peñadardized principal and daily atmospheric Schulte anomalies circulation (2014) of patterns anal- Episodes sea based of level on major during the floods stan- the inNorth summer the Atlantic months Central Oscillation of Swiss July Alps (SNAO;of are and Hurrell the triggered August. et Little by al., negative IceSNAO Summer phases 2003) Age during phases (AD the warmer during 1817–1851 climatetive the from SNAO and are AD last 1881–1927 related 1977 pulses to to flood present. cyclonesthey clusters) Floods of move north-east during Mediterranean and posi- origin along by the thatwith Vb cross positive track. central cold Floods Europe fronts during as originating negative over(Peña SNAO the et are Atlantic, associated al., tracing 2014). a northwest to southeast passage the last 200 yearsbacher (Peña and et Schulte, al., 2014) 2002; and Büntgen temperature et reconstruction (Luter- al., 2006; Trachsel et al., 2012) we infer that the interpretation is supported by theplutonic major bedrock. sediment yield from the higher catchment with because di For example, the maximumthe deforestation and second half damage of causedsedimentary the by 19th debris records century flows of (Willi, during themitigation 1932; Hasli–Aare of Marlot, river floodplain, 1915) management due are (in to not the recorded form the of in e embankments the and river correction). 5 5 25 20 10 15 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ect ff cult to ffi cult over the ffi erent floodplains are recorded ff O do not coincide with increased summer 18 3426 3425 δ O. Therefore, the geochemical pattern, traced with precision over 18 δ The interpretation of the comparison between sedimentary floodplain proxies and Deposition of siliciclasts with major contributions from plutonic bedrock (minimal fac- In the upper Aare catchment located on the northern slope of the Alps it is di As regards the low-frequency flood pattern at centennial scale (Fig. 8), geochemi- last 2600 years than overperiods the of peat 700 yr formation (from referencelate 450 period with to (Sect. 580, increased around 5.1). solar 800 For irradiance and example, and 950 calyrAD) some which corre- summer temperature andAlps late reconstructed spring-early from tree summer rings (Büntgen precipitation et al., of 2006, 2011) Europe is and more di the ative anomalies of forest recovery (Schulte et al.,assumed 2009a). to In be consequence, natural. rivers and flood dynamics are tor 1 scores, shaded areastime in Fig. lags 9) of occurred around duringcorrelate 30 solar closely years. minima with Apart or the occasionally from cooler with climate a in few Greenland cases, (North these Atlantic)the recorded aggradation last by 700 pulses neg- years also (Fig. 8),nium can of be flood assumed plain to dynamics. be Thisof valid outcome alpine for is the rivers, especially last because relevant two before forBernese and the 1100 a cal understanding Alps half yr millen- was AD relatively the human low impact and on sporadic landscape phases in the of clearance were followed by deposition of phyllosilicates (peaksreduced of flood factor activity during 1) warmer matchanalysis climate the pulses of (as maxima each already of shown core).horizons by TSI, To were the validate pointing separate compared the to to regional theIN-08, IN-30) signal data and obtained of Lombach from these floodplains the2008, (LB-10), proxies, Lütschine 2009a, where ages previous (cores b) studies of also IN-02, (Schulte indicated peat IN-04, Common et a periods al., coincidence of peat between formation soil between formationfrom the and 500 three solar di to activity. 450 cal550 yr calyrAD BC, around and 100 calyrAD,records around in from 800 calyrAD. 125 the to Lütschine 250activity, In calyrAD, such and as recent Lombach from river centuries have 450 correction been to and the the disturbed palaeoenvironmental draining by of the wetlands. impact of human temperature in Europe and the Alps (Büntgen et al., 2006, 2011). This observation may (TSI, Steinhilber et al.,depicted 2009) by formation over of the peatdark last and shaded organic 2600 years rectangles. soils (Fig. (lithostratigraphic Figure data) 9). 9 were illustrates Furthermore, shown that by periods periods of organic soil formation and When calibration by historical sourcesofloods has and been mechanisms possible, contained the in the informationValley floodplain about has sediment palae- been record shown of the to Lower beand Hasli 196 accurate years (Sect. of 5.1). the Because composite105, periodicities record of (Table 129 2) 80, are and 96, very 120 207 similar years) to we the solar plotted cycles (86, factor 1 scores alongside Total Solar Irradiance cal proxies of theto Hasli–Aare floodplain 1876. record Cycles four startof major phyllosilicates quasi-cycles during (positive from warmer scores), AD followed(around summer 1350 by 1380, climate floodlayers 1480, with conditions 1658, carbonate withgressive 1700 contribution increase the and in 1762 deposition material calyrAD). fromand the The ends high cycle with altitude a continues plutonic flood withat bedrock peak a around (negative defined pro- 1460, scores) by 1590, maximumperatures 1720 negative and in scores. 1850 These the yrcalAD terminations Alpset coincide al., (Büntgen with 2009) et minima and negative of al., SNAO summer 2006), trends tem- (Hurrell Total et Solar5.2 al., Irradiation 2003; Peña (TSI; et The Steinhilber al., possibility 2014). of creating a 2600 yr palaeoflood calendar establish a correlation, because major floodsand are negative recorded during NAO years phases. ofby However, both during a positive 11 the yr Little running Icescores mean Age correlate from positively NAO 1667 with values thecatchments smoothed to geochemical (positive 1820 flood F1 calyrAD. proxy scores) Factormode 1 deposited The (cooler during contribution winters). floods of correlate Afterwards,a siliciclasts with this positive trend, negative correlation from negative NAO disappears. F1 the Whereasof scores highest (flooding) considerably NAO warmer continue shows until summer AD temperatures 1867, on due melting to processes. the e 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − s 3 O variations and 18 δ level (a conservative estimate) 1 3.5). − ≥ s 3 1, whereas discharges of 500 m M ≥ M 3427 3428 Ti) peaks and Factor 1 anomalies. The determina- / O isotopes from the Greenland ice, temperatures and precipitation re- 18 δ C, TSI, At our present stage of knowledge, the attribution of individual floods to specific Focusing on the correlation with precipitation proxies, it is striking that from Figure 9 also illustrates the possible correlation of our data with the 2600 year long Spectral analysis of the geochemical and pollen time series and climate proxies The palaeoflood clusters defined by flood layers (e.g., 1300–1350, 1420–1490, 14 δ tion of historical floodonly discharges rough that estimations are defined presented. the Fromsume the damage that historical before threshold and AD instrumental is 1875 data complex, the we magnitude and as- of 351 m broadly follows the patternfor and which frequencies historical of sources floods are in available). the last 700 years (the period 6 Conclusions Our results suggest thatresolution deltaplain composite sediments palaeoflood of the seriesand Hasli–Aare, can related which mechanisms, reproduce be including the generated trends, fluvialments. clusters dynamic from We and high- gaps calibrated ofgeomorphological natural floods data in proxies by alpine textual compiled catch- and factualthe from sources termination and sedimentary, by of geochemical instrumental the data.fourteen and River Before historically Aare recorded Correction extreme incoarse-grained flood events AD layers, since 1875, log(Zr no AD fewer 1480 than were twelve also of identified the by produced damage of small-medium intensity climate pulses may beor uncertain characteristic without climate cross-correlation anomaliesdeposition with (marker during historical events). floods data To corresponds conclude, series quite alluvial closely flood to plain solar and pulses, whereas afterAD, the during outstanding the wet “Migrationized climate by Period” predominantly anomaly the dry spring-early from floodrecorded summer over regime 350 conditions. the This switched last to has 700 to years. been 450 cal consistently a yr pattern character- or higher probably caused catastrophic damage ( 400 calyrBC to 700 calyrAD floods occurred during both wetter and drier climate incidence of flood pulses2600 was to detected 1100 cal from yr 1100 ADnot calyrAD some be events interpreted to do as not present, alutely coincide. whereas However, complete clear this from mismatch observation that of should the thewhich outstanding two coincides flood curves. with gap For an example, in unusuallyshown it long-lasting the by is dry the Aare abso- dendrochronological late river data spring-earlyposite from (Büntgen summer sedimentary 450 et period lake al., to as record 2011), 580 calyrAD,low of is variability. reflected the in Swiss the Alps com- as a relatively calm phase with very 1550–1620, 1650–1720 and 1811–1851 calyrAD)the highest with plutonic contribution bedrock of areas siliciclasts occurred from predominantly during periods of reduced flood reconstruction based on flood deposits from ten lakes in Switzerland. A good co- ( suggest that peat formationwarmer is summer conditioned temperatures. by Furthermore, theoccurred during during timing the cooler of summer last flood climate 2600reference years pulses, gaps period as not rather (Figs. previously all than 8 shown floods by by andanisms the 9); of data flood various of processes the kinds,precipitation, are related controlled variations to by of drivers summer snowline, anddation) climate abrupt on mech- (atmospheric the temperature one circulation, rises hand,and type and and glaciers) to of permafrost on winter the degra- climate other, variability as (water discussed storage in by Sect. snow-cover 5.1. fluenced by the North Atlanticmentary dynamics floodplain and record solar illustrates forcing. that The periods compositefrom of 2600 minor organic yr floods sedi- soil and flood formation gapsarea) and inferred match deposition the of maxima of phyllosilicates Total (medium Solar high Irradiance. catchment construction from tree-rings,100, NAO, 120 SNAO) and evidence 200 years. similar Thus, the periodicities mechanisms of around the 80, flood processes are strongly in- 5 5 10 25 20 15 15 10 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 ≥ M 3430 3429 on slopes and consequently the discharges of alpine rivers. ff We are grateful to Niels Hählen, Civil Engineering Department Canton ect of snowmelt during short warm episodes within cool climate periods char- ff Evidence of the influence of atmospheric circulation dynamics on alpine flood fre- The results with regard to the compilation of a composite 2600 yr palaeoflood record flooding activity in Lakehydrology, Le Holocene, 15, Bourget, 420–428, France: 2005. a high-resolution sediment record ofund ihre NW Folgen, Alps Eiszeitalter und Gegenwart, 37, 109–118, 1987. European Alps, A.D. 755–2004, J. Climate, 19, 5606–5623, 2006. Herzig, F., Heussner, K.-U.,ropean Wanner, climate H., variability Luterbacher, and J., human susceptibility, and Science, Esper, 331, 578–582, J.: 2011. fluviales 2500 years en of los Alpes Eu- 2014. Suizos, Ph.D. thesis, University of Barcelona, Barcelona, Spain, 259, quencies is obtained whenvalley and flood indices of intensities atmospheric modes and AD geochemical 1670 to proxies 2000 are from compared. Floods the Hasli Acknowledgements. occurred mostly during positive trends(cyclones of of SNAO Mediterranean phases origin) or following shortative years positive SNAO or SNAO (North even pulses Atlantic decades front dominated systems).of by This neg- the combination e underlines the importance acterized by larger snow cover andthat glaciers. the This outcome 11 is yr also smoothedwith supported the negative by geochemical the NAO flood fact values proxycatchment Factor (i.e., 1 areas) cool (floods from winters) and AD major 1667 correlates contributions to positively from 1820. highest show that alluvial floodvariations plain broadly deposition following the during flood floodsbeit pattern responds with and a sensitively frequencies to larger ofthe climate margin the specification last of of 700 climate uncertainty. years, or Therefore, al- yond environmental palaeoflood the conditions information proxies that provided do by cause notpaleoenvironmental palaeoclimate extreme data. proxies, events permit but be- contribute complementary The Supplement related to this. doi:10.5194/hessd-12-3391-2015-supplement article is available online at Bern, for providing flood data and helpful expert advice. We thank Ulla Röhl and Thomas West- erhold (MARUM – Centreducing for in Marine the Environmental XRF core Sciences, scanningJuan University techniques Ignacio of and Santisteban, discussing Bremen) the Alexandre for XRF Badouxand data intro- and series. geochemical Gerardo We time thank Benito series also for and discussingmore, Alberto the we Martínez flood Monreal thank data for Marta mineralogicalout analysis. Baró geochemical Further- analysis Albos, and Maura helpedcollaboration Coca of in Sabater local the administration and field and retrievingthanks João property goes sediment Pedro owners to cores. Penilo concerning Hansueli We who and drilling appreciatemation, Sigrid permits. carried the logistic Balmer-Rose A support, (Wilderswil) special for plum providingpaigns. tart local The historical and flood infor- for damage their data hospitalityInstitute for during for the more Forest, period than Snow 1972–2010 10were and were downloaded field from provided work Landscape the by cam- Research IDAWEB theupper database WSL. Swiss Aare (MeteoSwiss). Federal Instrumental river Information of precipitation onof the discharges records the Brienzwiler of FluvAlps the gauging Research station Grouptution were (PaleoRisk; for obtained 2014 Research from SGR and the 507) Advancedof BUWAL. Studies was Education The (ICREA funded and work Academia, by Science 2011) the (CGL2009-0111; and Catalan CGL2013-43716-R). the Insti- Spanish Ministry References Arnaud, F., Revel, M., Chapron, E., Desmet, M., and Tribovillard, N.: 7200 years of RhôneBork, river H.-R. and Bork, H.: Extreme jungholozäne hygrische Klimaschwankungen in Mitteleuropa Büntgen, U., Frank, D. 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A.: Is there evidence for solar 5 5 10 20 15 25 30 30 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Flooding of the entire valleyand/or bottom of areas at distancechannel to Fatalities, migration, interregional assistance, donations, poverty, food shortage, etc. Subsequent action: policy, river regulation, etc. Short-duration, local flooding Flooding at several stretches ofriver, the small pounded lakes Evacuation, people flee from flood Low number of fatalities – – – – – – – 3438 3437 Loss of productive farm landmassive due aggradation to and major shifts of river channels Severe damage or destruction of several buildings or entire villages Flood and minor damage is reported Damage or destruction of abuildings few close to the river Damage to hydraulic infrastructure (e.g., bridges and levees) Aggradation on landforms close to the channel Primary indications Secondary indications – – – – – – ) i M Categories of historical Aare floods in the Hasli valley. and AA Versammlung der Oekonomischen Gesellschaft inerei, Meiringen H. den Ebinger, 23. Meiringen, Mai 64 1880, pp., Buchdruck- 1932. a pioneer geo-engineering project:Lake tracking Thun the (Switzerland), Sedimentology, Kander 58, River 1737–1761, deviation 2011. in theAlps sediments – of solarQuaternary forcing Sci. and Rev., 80, evidence 112–128, for 2013. variations inropa, North Wasser Atlantic Energie Luft, atmospheric 103, circulation, 193–203, 2011. M 3 Event category ( 1 2 Table 1. Willi, A.: Die Korrektion der Aare und Entsumpfung desWirth, Haslitales, S. Referat B., gehalten Girardclos, S., in Rellstab, der C., and Anselmetti, F. S.:Wirth, The S. sedimentary B., Glur, response L., Gilli, to A., and Anselmetti, F. S.: Holocene flood frequency across the Central Zbinden, E.: Das Magdalenen-Hochwasser von 1342 – der “hydrologische Gau” in Mitteleu- 5 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | = 6 Flood dam- age index 1766; yellow Aare tensity = 650 650 470 208 1600 – Factor 1 Factor 1 Factor 1 Flood in- 5 (AMJ) P Peña and Schulte (2014). 5 6 (JJA) Tree-ring Compos. AA-2 AA-5 AA-10 Hasli– T 3440 3439 5 Büntgen et al. (2011); 5 (JJA) ring T 4 post 1499; green 1578 – pre 1762; blue (JJA) Reconstr.Tree- T = 4 Lutherbacher et al. (2002); 450 650 650 1200 950 2600 2600– NAO 4 3 O 18 GISP 2 4785 δ 2 Stuiver et al. (1997); 3 TSI 2600 1575– 1 14C δ 1575– 4785 104– 105 129 105 – 100 110 – – – – – – 130 139 96 100 120 95 – 102 – – – 105 – – 1251–1499; orange = post Aare Correction in 1875. = Steinhilber et al. (2009); 2 Geology of the Hasli Aare catchment and DTM of the Aare delta plain in the Lower SolarGleissberg North Atlantic 81Suess Europe 86 211 81 207 80 208 Alps 78 – 78 – Lower Hasli Valley (Aare) – – – 200 Switzerland 192 80 84 196 205 78 190 86 184 89 (175) – – Comparison of periodicities of palaeoclimate time series and alpine delta flood proxies Reimer et al. (2004); Proxy Cycles Period (yrcalBP) Periodicities – – 69 65 61 64 65 – – 63 – 60 60 – 1 Hasli valley showing location ofmentioned retrieved in cores text. Below: (black evolution dots). ofmaps, Labeled Aare field dots River survey palaeo-channels represent reconstructed and key-cores from documentarydiscontinuous historical sources (this paper). Age of reconstructed channels: red Figure 1. 1800; white (Bernese Alps). Table 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (d) silty fine Factor 1 = (f) 0.9 and coarse- and − > (e) Ti) values / coarse sand) of core AA-10. = log(Sr 0.1 of core AA-10. (c) − > 3442 3441 0.5 and coarse-grained flood layers (ufS middle sand; gS Ti) values − = / > Ti) values / middle sand) of core AA-05. fine sand; mS = = log(Zr (b) Lithology, chronology and geochemical stratigraphy of key core AA-05. The bars fine sand; mS Chronostratigraphy of core AA-05 and AA-10 and comparison with historical Aare = Flood data series reconstructed by historical sources (columns) and archaeological data sand; fS scores of chemical composition of core AA-10 and AA-05 samples (reverse). floods in the(a) Hasli Valley. Time series are plotted in calibrated calendar years (cal yr AD). Figure 3. (dashed column). grained flood layers (fS Sand fraction (630–2000 µm) and log(Zr Figure 2. represent organic horizons and beds. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3444 3443 O isotope record from Greenland Ice Sheet (GISP2; Stu- 18 δ Scores of scanned Core AA-02 samples and grain size are plotted Factor 1 scores of scanned Core AA-02 samples from 2600 to (a) (c) (b) Comparison of 2-D-plots of factor loadings (factor analysis) of chemical major and minor elements, 1600 calyrBP. Correspondence of coolsigned climate by pulses dashed and lines. siliciclasts (negative values) are as- Figure 5. iver et al., 1997) and for comparison. Figure 4. total organic carbon (TOC) and grain size fractions of core AA-02 and AA-05 samples. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | > Flood (a) Composite flood (c) (left scale; referring to Table 1 and M 3446 3445 . (a) Red noise spectra of the composite palaeoflood record. Dotted line shows (b) Harmonic analysis of the composite palaeoflood record of the Hasli–Aare delta (right scale) recorded at the Brienzwiler gauging station are valid for the period Flood chronology of the Aare river in the Hasli Valley from AD 1480 to 2012. 1 − s 3 Hydro-climatological cause of floods (legend below) according to historical written sources, Eq. 1) are estimated300 for m the periodAD AD 1908–2012. 1480–2012, Discharge whereas maximum measurementsof annual in the discharges AD Aare 1875 correctionby structural were project. mitigations conducted Measured such on-site as dischargesreservoirs river by since and embankments AD engineers event since 1932 AD as intensity 1875 inof level the and the case are retention Sankt of capacities influenced the Michael of 2005(b) church flood (arrows). by Triangles flooding represent damage and severe aggradation caused by the Alpbach river. WSL flood data bank, expert reports, newspapers and precipitation data. Figure 7. intensities reconstructed from documentaryand and instrumental geomorphological data evidences (red (blue columns). columns) Event intensities frequencies. Data as in false-alarm level. Significant frequencies are shown in years. plain. Dotted lineshown represents in critical years. level for the Siegel test and significant frequencies are Figure 6. (a) Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (c) 40 yr middle (b) = Variations of Annual strato- (d) (a) Composite sedimen- fine sand; mS (c) = 40 yr averaged variations of To- (a) 11 yr smoothed JJA temperature anoma- silty fine sand; fS (b) = Flood chronology derived from flood deposits of 3447 3448 (f) Sedimentary palaeoflood proxy from the Aare delta (d) Comparison between reconstructed palaeofloods in the Hasli Valley and solar and Comparison between historical flood reconstruction of the Hasli–Aare and solar and Historical flood chronology of the Aare River (Hasli valley) from documentary, archae- 11 yr smoothed AMJ precipitation anomalies in Central Europe reconstructed from (e) (e) O of the GISP2 ice core from Greenland (Stuiver et al., 1997). 3-data smoothed biannual 18 spheric volcanic sulfate aerosolaveraged variations injection, of Northern Total Solar Hemisphere Irradiancetary (Steinhilber palaeoflood (Gao et proxy et al., from 2009). al., thescores Aare 2008). of delta chemical plain in compositiondark the of shaded Lower delta rectangles. Hasli valley Stars plain (this indicateδ samples. paper). the Peat Factor stratigraphical 1 and position organic ofdata. soils datings. are shownoak by ring width series (Büntgen et al., 2011). ten lakes from the northernGlur slope et and al., central 2013). area of the Swiss Alps (50 year moving average; sand). ological and geomorphological evidences like inof Fig. the 7 Sankt (this paper). Michael Triangles church represent damage by flooding and severe aggradation caused by the Alpbach river. Figure 9. volcanic activity and climate proxies from 600 calyrBC to 2000 calyrAD. 11 yr smoothed AMJdensity precipitation series anomalies (Büntgen in etplain the al., in the 2006). European Lower Hasli Alps05 valley reconstructed (this samples paper). from and Factor 1 coarse larch scores grained of flood chemical layers composition of (ufS core AA- tal Solar Irradiance (Steinhilberinjection, et Northern al., Hemisphere 2009) (Gao and etlies al., annual 2008). in stratospheric volcanic the sulfate European aerosol Alps reconstructed from larch density series (Büntgen et al., 2006). volcanic activity and climate proxies (1300–2010 cal yr AD). Figure 8.