Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 7410 7409 , and K.-F. Wetzel 2 erent questions concerning climate variability and flood ff , R. Glaser 1 , J. Jacobeit 1 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. Institute of Geography, University of Augsburg,Institute Augsburg, of Germany Geography, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany transition from the post Little Ice Age period to the Modern Climate Optimum around 1730–1780, 1820–1870, and 1910–1955 asThe well flood-rich as periods in a arerich 9th characterized and period by beginning flood-poor longer in periods floodconnected 1980. (in durations. to Most particular changes of the innumbers the beginning (as natural flood- and a climate measure the of variability. endas solar These of activity), include well so-called them) Little changing can as Iceexternal sunspot Age be forcing changes Type Events factors, which (LIATEs) in couldin be the used the to Bavarian North explain Alpine the Atlantic Foreland,such changing end flood as Oscillation in frequencies the 1930. (NAO). Relationships correlation within Climate of the flood signals climate system frequencies from with the NAO have changed during the the Alpine Foreland of Germany, summerwritten floods historical prove sources, to the be mostreconstructed flood important. history back Based to of on the therich” Alpine 14th and Foreland century. “flood-poor” of One Germany episodes majorrecorded can in result in be nearly the is periods cyclical the 1300–1335, sequences. occurrence 1370–1450, Flood-rich 1470–1525, of periods 1555–1590, “flood- 1615–1665, were varying due to altering climatic conditionsdiscussions since historical whether times? man-made In the climate contextfrequencies, of change recent a will modify look thefloods back present into in state the general of pastvariability flood and and is of changes essential recent inseries. to floods a understand A in comprehensive the particular. perceived way,since occurrence it In increase of is 1997 order necessary of requires tofrequencies to summer examination understand in review of floods climatic long a long proper time in way. time eastern In series view Germany of to and the estimate annual Bavaria changes distribution of in flood flood events within This paper describes theGermany flood and history addresses of di frequencies the from Bavarian the part 13th offlood century the frequencies until Alpine within today. Foreland Will of the recent Bavarian climatic Alpine change modify Foreland the or are the flood frequencies Abstract Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/11/7409/2014/ 11, 7409–7440, 2014 doi:10.5194/hessd-11-7409-2014 © Author(s) 2014. CC Attribution 3.0 License. Flood history of the BavarianForeland Alpine since the late Middlecontext Ages of in internal the and externalforcing climate factors O. Böhm 1 2 Received: 28 May 2014 – Accepted: 2Correspondence June to: 2014 O. – Böhm Published: ([email protected]) 3 July 2014 Published by Copernicus Publications on behalf of the European Geosciences Union. 5 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ff erent European flood histories with erent parts of Central Europe have ff ff ected the Bavarian Foreland. ff 7412 7411 erent parts or catchment areas of Germany, while Rohr (2008) ff ects the investigation area in total). For the past, this can be seen from ff All the rivers coming from the Northern Limestone Alps traverse the Flysch Zone, To generate a long time series, it was necessary to integrate three di The Bavarian part of the Alpine Foreland of Germany (hereafter termed Bavarian enter the areamoraines of and gravel the fields. The faulted substratum Molasse of the sediments lower sections and of the cross rivers is the formed belt of Pleistocene In this paper theareas Bavarian Foreland of is the defined aforementionedby by rivers. the the From river lower west sections Iller toin of (in east Fig. the the the 1. catchment west) The research and headwaters,northern-alpine area the however, rivers is are mountain located Inn bordered rivers in and (apart theas Salzach a Alps from (in foreland so river the river). that The east) Wertach all mainDanube as which of rivers river. depicted Iller, the should Lech, rivers be Isar are and regarded Inn are Alpine tributaries of the merged for one overallForeland time includes more series. than The 550 timeline individual flood of events the (see methods’ flood section). history2 of the Bavarian Investigation area and compilations. These written recordslate can Middle be Ages analysed as inavailable depicted a from statistical in the way Glaser so-called since (2008). the earlyFor From at instrumental the least period year one (EIP) representative 1826considered, gauge (cf. onward, recorded station Jacobeit historic data in et water are the level al., records lowerof 1998). can sections be of the evaluated. every From alpine the 20th river beginning discharge century measurements) are available. up The separately torivers evaluated flood Iller, the histories Lech of present, the with tributary modern Wertach, instrumental Isar, Inn data and (water its level tributary and Salzach have been following summer floods of 2002 (Elbe/Danubefloods Flood) (despite and their 2005 special (Alps naming) Flood). have All a these periods of flooddescriptive documentation. period and The has oldest been obtained information from comes historical from writings such the as so-called chronicles Flood) 1999”, both of which took place at the end of May, can be compared to the 1997 has experienced numerous floodsmonths. triggered The by so-called Vb-conditions “(River) during Oder Flood the 1997” summer and the “Pfingsthochwasser (Whitsun Foreland) has constantlystrong experienced floods flood as events,standard well but reference as periods the of forbeen return 30 triggered flood-rich years. periods by All or e.g. cyclonesso-called of flood-poor following for Vb the a periods cyclone recent track special cannot major seemsevents pathway to summer be in (cf. be floods van derived the the have Bebber, maincyclone by Bavarian 1891). condition a Foreland, This causing catastrophic currently flood reconstructions and of historic also weather in patterns (cf. the Böhm, 2011). past The (but recent period not since every Vb a focus on Central Europe. Nevertheless,Foreland the flood has history of not theAdditionally, entire been the Bavarian Alpine Bavarian analysed Alpine into Foreland climatic a represents changes a (cf. systematic Auer region et way with al., until 2007). a high now sensitivity (cf. Böhm, 2011). Historical climatology, especially theincreasing branch interest addressing during historicalbeen floods, the has investigated. last gained decades. For(1984, Di example, 1996, Schmoecker-Fackel 1999) andexamined analysed the Naef flood the history (2010) flood ofet the history and Czech al. Republic, of Böhm Pfister (2004), and Switzerland,(2008) Deutsch Wetzel (2006), investigated Brázdil and Mudelsee di et Pörtgeexamined al. (2001, (2005) extreme 2002), Deutsch naturaland et events Glaser al. in and (2004), Austria Stangl and (2003a, including Glaser b) floods. analysed Sturm di et al. (2001) climate change. 1 Introduction 1930. Natural climate variability might have been outperformed by anthropogenic 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er ff , 2000–2002; Brázdil, ff in the region of the Danube river up 1 from the headwaters into the Bavarian − ff 7414 7413 erentiate spatial and chronological aspects of ff ect hydrological interpretations concerning the ff erentiate the Little Ice Age into so-called Little Ice Age ff ers from around 600 mm a ff and more within the highest elevations of the investigation area. The 1 − The investigation period 1300–2008 covers the Little Ice Age (1300–1850) and the Due to the spatial distribution of the catchment areas within the northern Limestone In the Bavarian Foreland we can di 2008) which wereinstrumental re-examined records in with the Bavarian Foreland a started with focus the on year 1826. More the than 20 Bavarian Foreland. The early to the yearand 1880. chronicles The (e.g.Wissenschaften/Historical the evaluated Commission “Historische written ofpublished the Kommission evidences 37 volumes Bavarian der originated of Academyprint Bayerischen city from of chronicles Akademie media, handwritings between Sciences” der 18621987; has compilations and Fliri, 1968), (e.g. 1998; annuals,2005), historical Stahleder, Sonklar, unedited 1995–2005; historical Börngen 1883; leafletAdministration and database Weikinn, of (Schorn, Tetzla Inheritance) † 1958–1963; and 1937; Ferdinandeum already Innsbruck Alexandré, existing databases (Militzer, 1998; Glaser, Augsburg (Lech/Wertach), Munich (Isar),Within Wasserburg the (Inn), framework Burghausenproject, of (Salzach)). a a database calledwas DFG developed IBT in (German (Inundationes cooperation Research Bavariae with2008). HISKLID Thesaurus) The Foundation) (historical (cf. first funded climatic investigation Böhm, database period research 2011) – was cf. the Glaser, descriptive period from the 14th century periods, starting with LIATE3,and are 1810–1850. descripted for the years 1300 –1380, 1570–1640, 3 Database The body of historicalthe source northern material alpine isone mountain due to rivers. notable the All historical wide of site range the of (among above-mentioned settlements a rivers along host multitude at of least other sites, e.g. Kempten (Iller), substantially to each other (cf. Figs. 5 and 7). transition period to the Modernet Climate al. Optimum (2000), as it found is today.Type advisable According Events to to (LIATEs) addressing di Wanner three major periods of extended glacier tongues. The The flood-rich periods of the summer months and of the whole year correspond peaks (rivers Inn anddistribution of Salzach). the This flood spatial events indicated distribution in is Table 2. reflectedAlps by and the the seasonal Bavarianthe Foreland, eastern the river highest sectionsand proportion of Lech Inn of (57 %). (79 summerand %) Due floods Wertach and to occurs only Salzach have the in (73summer about %), lower floods 40 followed % extent to by of of the Isarinformation floods annual alpine is (58 during %) owed time catchment summer. to series In area, minimized can total data the a be quality rivers and dominance stated. information of Iller Hereafter before the the 16th use century. of annual into the individual catchments.chronological We annual can mean observeinvestigation a discharge area west-east with maximum a gradient spring starting contrasting peakriver (rivers in the Lech Iller and the and Isar, Wertach). located western Thea in catchment part the distinctly areas central marked of or part summer of the peak the followed investigation to area, the are eastern denoted part by with prolonged summer a high-pass-filter has beenprecipitation applied totals (see di methods). Theto regional distribution 2500 mm of a annual share of alpine catchment isForeland important for due runo tobarrier. its In Table 1 function the as reference data temporary of the water relevantflood rivers storage genesis are as listed. a reservoir function of and hypsometric distribution orographic and thereto linked snow retention in their east-to-west extension.segments The are geological of formations particularsubsoil of interest and the because anthropogenic of outer encroachments their alpinethemselves. texture. after stream These Due 1850, circumstances to the theEIP. a To riverbeds assure texture homogeneity have of in deepened the the comparison of flood events of individual time series, by sandy sediments of the Molasse trough. All traversed geological formations di 5 5 25 15 20 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent river ff 0.86) between the data = r cient ( ffi 7416 7415 erent data periods, we used the following approach. To compare ff To create a wide data base as possible, the time series “flood frequency of the To merge the di the administration did notinstead change extended the the datum measuring of sticks the of the measuring gauges device into for the a negative time, range, but a total descriptions. Therefore, floods can act as an indirect climatic indicator. 4 Methods In Fig. 2 the monthly(35 km maxima of south water of levelsFigure of Augsburg) 4a the before shows example (a) gauge theinto Ettringen/Wertach and deepening the after of river system. the (b) The riverbed high-pass beginning due of filtering to this are anthropogenic deepening depicted. took encroachment place around 1860. Since hydrological events. Withinhas the an range exceptional position.damages of Common which historical threads have climatic connectingthe led NCA all data, to is flood flood burdens basedto informations on information on are the former the particular neighbors. reasonable burdens The assumption that main – historical argument contain flood for more reports objective – information due than other climatic Bavarian Foreland” usesBavarian all Foreland flood which couldwithout events source-critical be of verification. gathered the This duringinformation process outer due the minimizes to alpine descriptive the anthropogenicnot period, loss river or varied natural of with sections historical calamities. historical and records, To in flood we avoidpractice refer the the verified to usual a criticism inter “non to (cf. critical alia approach” Böhm, by (NCA), a 2011). cross-comparison methodical with The verified NCA records, is e.g. a HISKLID procedure especially designed for extraordinary considered, whereas Level 1 events fromoverlapping the period instrumental (1826–1880) period were between disregarded. thesuggested An descriptive this and procedure. the Samples instrumentalshown of periods that rudimentary the descriptive traditional flood ofon information historical strong flood have events information (cf. Böhm, through 2011). time are mainly based information, all floods of the descriptive period from intensity Levels 1, 2 and 3 were data were used, see methods). According to experience in working with historical flood of water-related structures (e.g.was bridges, reported weirs or and ifwas mills) there assigned or were to buildings indicators the nearsystems, for flood. the long-lasting associated Catastrophic rivers flooding floods, with of asloss severe a farmland, damage of rule Level or 2 reported lives, destructionthe from long-lasting di of fluvial flooding water-related system, of structures, based wide were on areas the classified monthly and asmeasurements maxima plus geomorphological Level of one, water changes two 3. level or in classification The or three standard discharge. of selected deviations The the define instrumental mean the instrumental values thresholds data data for of the are these (in case of water level data high-pass filtered of historical floodsscheme which of was Sturm adaptedlevels. et to The classification al. the is based instrumental (2001), onevents the period. damage were reports flood According and mentioned weather events to descriptions. onlyonly were If the by minor, flood classified the rudimentary into event descriptive was three information classified intensity as or a damage regional was flood (intensity Level 1). If damage (Iller), Landsberg am Lech (Lech),(Salzach). Landshut The (Isar), EIP Wasserburg time (Inn) series andperiods, of Burghausen verified the by river a Wertachfrom high was the Pearson gauge merged correlation stations between Ettringen coe overlapping andwere Augsburg/Oberhausen. From available 1900 from onwards the data Bavarian Water Authority. flood events from written historicalor discharge sources during with the flood instrumental events period, measured we by used an water existing level intensity classification to monthly maximaof of gauge water stations, level. therepeatedly). Due gauge To homogenize to datum the haspaper physical data, been structures we a changed and choose high-passlongest in vertical filter one some coherent was erosion cases representative time applied. (sometimes series gauge In since the station 1826. present for They each include river, the each time series with of the Kempten historical gauge station records were examined. The data were analysed with respect 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | test in t erent databases and data densities (e.g. ff 7418 7417 erent changes. erent historical sources and locations which refer ff ff erent data density from early historical times until the present ff level of 0.05 (solid line) is depicted in Fig. 4. Most of the detected fracture α The determinations of flood-rich and flood-poor periods are based on a polynomial To better understand the long-term development of flood events in the Bavarian The first flood-richchanges period, in though the atmospheric with framework. a Wanner low et al. data (2000) density, are can dating be the onset associated of with of the inventionorder of to letterpress. prove Single significantfrequencies changes flood-rich of within periods the the Bavarian will time Foreland,Fig. series be we 4 of have (cf. discussed depicted Glaser the below. and the 31the year Stangl, In estimators NAO 2003b). running of index In flood- the and this the context,discussion changing sunspot follows climatic numbers subsequently). parameters will like be approached briefly (a5.1 more extensive Flood-rich period #1: 1300–1335 In Fig. 3depicted. the Based flood history onflood-rich of a and 8 the polynomial flood-poor Bavarian periods functionbest can Foreland in be of between identified. view the The AD of 1300day. polynomial 5th the function A and matches di degree 2010 rising (see is data the density red after line), the 9 mid-15th- century must be seen in a context frequency time series ofreconstructed the NAO Bavarian index-values Foreland (cf. has Luterbachermean additionally et sunspot been al., numbers 2002) (data correlatedbetween as after with Hoyt well these and as quantities Schatten, withWerner, 1997). include moving 2002). Significant the correlations consideration of inherent autocorrelations (cf. 5 Results The time series forwhich can the identify Bavarian fracture points ForelandThe within has the been time series submitted (cf.points to Glaser coincide and a with Stangl, two-sided changes 2003b). in t-test atmospheric conditions (see next section). The flood 4.1 Statistical significances function of the 5th degreegeneral, for the the running intervals flood frequencies above/belowpoor (see the red function periods. graph graph in Due Fig. arenecessary 3). defined to In to as interpolate the flood-rich/flood- in14th/15th changing some century data cases. – Di basisperiod) the were over period thus the considered of as entire the well as Renaissance time possible. – series, beginning it of was the instrumental considered. For example, thebiggest summer floods since flood the of beginninga of the flood written year mark records is 1501 (quantitativethe evidence located which in at IBT terms was the more of one “Fischmarkt” thanflood in of 150 frequency Passau, the times. of Bavaria), This the has Bavarian event been Foreland. is recorded counted in only once in the 31 year running Foreland, normalized 31 yearmany running earlier flood studies frequenciesBavarian (e. have Foreland, all been g. flood calculated Glaser,overall events as 2008). within time this in series. To study To revealto area integrate the have one di been flood meteorological merged history event,days into before a one of and time-window after the including aduration entire of designated a hydro-meteorological event sequences maximum has (from the number beento genesis introduced. of of the synoptic Therewith termination seven disturbances the of varying flood waves) as well as the blur of historical informations can be first counter-measures (like lateralAround water-buildings) 1885 obviously the occurred incisiontwo around seems datum 1870. to changes be can stopped.suitable method After be to a identified. address short these The di data high-pass gap filtering around seems 1895, to be the most riverbed incision of more than 6 m within 30 years can be documented. Furthermore, 5 5 20 25 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ect the flood ff test estimators. test value shows t t -level 0.05) as well α first grey bar in Fig. 5) is = test estimators as well for the t test estimator indicates significant values t 7420 7419 test estimator, a possible evidence for unsettled t -level of 0.05) at the beginning and significant values at the end of period #4 α 2.00 at From 1500 onwards we can use reconstructed NAO-Index (NAOI) values (cf. test estimator values. The maximum value is accompanied by the end of the Spoerer > numbers which have been directly observedabsolute for the minima first of time since sunspots 1610 starting (cf. Fig. in 6). The 1660 turned into the Late Maunder minimum Period #5 isbeginning again as for accompaniedand the by the ending Maunder significant (seea Minimum Fig. (1645–1715, conspicuous 4). cf. behavior Theatmospheric Schönwiese, of conditions. transition 2008) Period the period #5 is tooket between accompanied place al., period by during LIATE 2000); #5 2declining the (1570–1640, cf. flood retreat Wanner of frequencies. the Period glacier #5 tongues also (peak fell around into 1650) a coincides period with of declining sunspot (not shown) and summer( (cf. Fig. 7). The (cf. Fig. 4). Thetemperature flood anomalies frequency that maximum lead coincides into with LIATE2. a distinct period5.5 of negative Flood-rich period #5: 1615–1665 NAOI is more significant during the winter than the5.4 summer half of Flood-rich the period year. #4: 1555–1590 Between the years 1550 andlow 1700 index-values. the Within normalized this NAOI(see period, is Fig. generally variations characterized 5) in by falling with flood NAOI-values, respectively, frequencies increasing for the can and whole be year declining as identified well values as being for the accompanied seasons of by winter rising and Luterbacher et al.,accompanied by 2002). an obviously Theseasonal declining values end NAOI (Fig. for 7). ofyear annual Due on (Fig. flood to period progress, 5) the the as full #3 impactconditions. year well development of In of ( as precipitation the general, NAO summer to however, may the the reflect mean entire correlation weather hydrological between weather conditions and the frequencies in the Bavarian Foreland. 5.3 Flood-rich period #3: 1470–1525 The transitional period betweencoincides the flood-poor-period with #2 an andas obviously the with rising flood-rich-period #3 the estimator(cf. end (significant Wanner of at et a the al.,t 2000). distinct The period end of ofMinimum, negative period again temperature #3 an anomalies is indication marked in for again the changing by Alps climate highly conditions significant which a The increase ofDespite flood the absence frequencies of significant is estimators,changing the climate accompanied end of conditions by period characterized #2another significant coincides by sunspot again the with minimum beginning between of the years the 1450 Spoerer and Minimum, 1534 (cf. Glaser, 2008). significant changes with the beginning andduring the end the of Period flood-active #1. phases Theapproaches estimator a (this declines climax, can the be floodinput frequencies verified decline into for considering the a most alpine timepoints of glaciers lag in due them). (cf. Fig. to Wanner While mass 4 et LIATE3 coincideperiods al., in with 2000). Fig. the Most 3. beginning of and the the significant end fracture of5.2 the flood-rich or Flood-rich flood-poor period #2: 1370–1450 triggered by multipleLIATE3, a volcanic first eruptions. period of Period advancing glacierenhanced #1 tongues by during the coincides the Wolf Little solar with Icethe activity Age, additionally the minimum sunspot (1282–1342, beginning cf. numbers Glaser,coincides of after 2008). with Following a Usoskin period et of sunspot al. minima. (2004), According to the Fig. first 4, the flood-rich period exactly the Little Ice Age at the beginning of the 14th century, based on Miller et al. (2012), 5 5 20 25 10 15 20 25 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | test t test estimators, t erent overlapping trends. ff erent pattern. The absolute ff test estimators (cf. Fig. 4). The t test estimators with a last significant test estimators during increased flood t t 7422 7421 test estimators in general will not show significant variations for the t test estimators reveal this transition at the beginning of the period (unique t The development between LIATE1 (1810–1850) and period #7 requires a particular The following flood-poor years until 1820 are characterized by a next The flood frequencies are rising while the mean NAOI-values for the full year are correlations) between floodthese frequencies time series and seem to sunspot be decoupled, numbers as do depicted in exist. Fig. 6. Thereafter The beginning of period (cf. Figs. 5frequencies and and NAOI 7). values. Theimpact In and this following significance context of years we thein are summer can the NAOI Bavarian generally characterized for Foreland identify the (discussion by an development see of increasing below). both flood frequencies declining5.8 flood Flood-rich period #8: 1910–1955 Period #8 isestimator-value again within framed the by significant time series (see Fig. 4). Until 1930 similarities (or whereas the precedingcorresponding LIATEs flood-rich (# periods. The 3 maxima of andof the preceding #2) low LIATEs fall into flood did intervals frequenciesA not noticeably framed end aligned by development at between thecan the the end NAOI-values be same and and highlighted the time the for flood like frequencies the beginning the whole of year flood-rich as periods. well as for the summer and winter seasons natural river systems. Thus, period #7The falls into a section of di estimator values, seecan Fig. be 4). interpreted as TheModern inhomogeneous Climatic end Optimum. climatic The of conditions increasingincreasing flood-frequencies during the of sunspot the period numbers period, transition #7 (cf. coincide Fig. based to with 6). the on reflection, because LIATE1 and the flood-rich period end at about the same time, Period #7 is marked byand a early changing instrumental database period). (transition Inperiod addition, between between it documentary the represents end period the ofOptimum beginning the as of Little well the Ice as transition Age the and beginning the beginning of of (systematic) the anthropogenic Modern interference Climatic into the 5.7 Flood-rich period #7: 1820–1870 reasons for this will be explained below. frequencies and NAOI-values, but duringdecline the in flood a frequencies’ distinct peakglacier way the tongue (cf. NAOI-values movements Fig. shows 5). a The slight development stagnation. of the Littlesunspot Ice minimum, Age in theaccompanied terms Dalton of by Minimum relatively (1790–1830, lowMinimum flood cf. and frequencies the Schönwiese, (see beginning 2008),flood Fig. of frequencies again 3). the (cf. next The Fig. 3) flood-rich end as period of well is the as accompanied extraordinary Dalton by extreme Period #6 isfrequencies; again the marked end ofvalues. by the The significant period isnext marked 80 by years a (cf.of distinct Fig. the evolution 4). NAOI-values. of The the Period whole-year estimator #6 development shows is a accompanied parallel by increase a of flood noticeable development declining; the flood frequency peakdecline coincides of with minimal the NAOI-values. The floodand following 7). frequencies The is development accompanied ofmaximum the by value winter rising of NAOI NAOI-valueswinter reveals flood (see a NAOI. frequencies di Figs. This coincides 5 water could with retention be which a could an short-termed favor summer indication increase floods for during of snow wet5.6 the melt. winter conditions Flood-rich resulting period #6: in 1730–1780 vast With the beginning ofcorrelation direct between the sunspot 31 year number movingperiods observations, sunspot numbers until we and 1930. can flood-rich and The refer flood-poor Minimum, to end compare Fig. a of 5 distinct LIATE and 2 Wanner coincides et with al. (2000). the beginning of the Maunder and were accompanied by the absolute flood frequency minimum from 1500 till today. 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ff 0.01). After 1930, ect the large-scale = ff erent sign) coincide α ff cient amounts to 0.62, ffi erent authors. According to ff er with respect to the sign of ff ect on climate development within ff ect the flood frequencies in the Bavarian ers amongst di ff ff 7424 7423 1280–1340) coincides with the first calculated flood-rich ∼ ective sample size based on a method by Werner (2002) which regards ff climatic conditions in detail Not all flood-rich and flood-poor periods can be connected to sunspot minima or With the beginning of the Maunder Minimum period the relationship changes its sign. The Wolf Minimum ( The duration of the Spoerer Minimum di the statistical persistence of database-inherent autocorrelationsthe ( relationship of sunspotA comparison numbers of and global flood temperaturesshows and a frequencies GAR temperature seems (Greater leap to Alpinesince over Region) the be the temperatures beginning calculated decoupled. of neutral-point the temperature early development instrumental period (cf.maxima, Auer et but al., 2007). allconditions sunspot independent extremes of its can trends be (cf. Böhm, connected 2011). to changes of overall climatic in a similar1830) way. again The shows coursebetween a the of years similar 1610 both development. andbetween 1995 graphs These the 1700 Pearson data during correlation and coe indicate theusing 1930 a the Dalton to e significant Minimum 0.7. trend, (1790 Considering – autocorrelation could be achieved by Glaser (2008), the Spoererwhereas Minimum takes Schönwiese place (2008) betweendefinition identifies the of years the the 1450 years Spoerer andrich Minimum, 1400–1510. period 1534, another (here According period sunspot #3). to minimumflood According to frequency coincides the the maximum with sunspot first of data aof of period flood- the Usoskin #3 et Spoerer also al. Minimum. (2004), corresponds the to the low sunspotAs numbers depicted in Fig. 6 running flood frequencies and sunspot numbers are varying minima encompassed within the investigation period, we can chronicle theperiod. following: This temporalnumbers correspondence is between unique within high the total flood time activity series (cf. and Fig. low 3). sunspot a special position which will be discussed later on. Considering the four sun-spot in 1610 and ending with the years around 1930 (cf. Fig. 6). The year 1930 occupies with changing climatic conditionsForeland. Within which these a relationships,not one discussed conspicuousness at this must point.reconstructions be It emphasized based has but to on be proxythe distinguished data. correlation between direct between Both observations flood periodsobservations and frequencies di started, and solar highwhile activity. afterwards In flood flood-rich general, frequencies periods beforebetween coincided direct coincided the with 31 with increased year solar running reduced activity. frequencies The solar is best achieved fit activity, with direct observations starting Feulner, 2011). Generallyatmospheric the circulation variability including ofand climate solar transpiration parameters activity (cf. likein can Endlicher temperature, a which precipitation and waythe Gerstengarbe, solar research 2007). Despite activity area, the it could uncertainty can have be an shown e that solar trends (of di to the use of 31 year running quantities, its5.10 validity remains unclear. The flood frequencies of the Bavarian Foreland accompanied by5.10.1 di The correlation of flood frequenciesThe and meaning sunspot numbers of varyingof solar activity fierce for the discussion climate conditions (cf. is Shindell currently a et matter al., 2001; Feulner and Rahmstorf, 2011; a parallel development (cf. Figs. 5 and 7). 5.9 Flood-rich period #9: 1980 –A ? last flood-rich period starts in 1980 intersecting with the end of the time series. Due #8 coincides with rising NAOI-values, the amplitude of these values in general shows 5 5 25 20 10 15 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ect ff 0.01) = α tests). These t 0.65, = r 0.01). The changing sign in = α 0.8 ( = r 0.01) and 1900–1999 ( 7426 7425 = α 0.78, = r 0.8). Further-more, the years from 1830 to 1999 exhibit another cients do exist. For this special period a statistical unique coherence ffi = r erent climate proxies and historical observations and transmissions. ff The NAO is of particular importance for the climatic conditions in the Bavarian The investigation period commences amid the latest climatic depression of the The annual and the summer time series of flood frequencies and of NAOI-values within the present work can be emphasized. NAO alone cannot explain theRegion very (GAR). sophisticated climatic The events presentmajor of the work atmospheric Greater describes Alpine conditions. multipleflood With mechanisms frequencies a the with shifts view influencesimportant themselves to towards within role the multiple in climaticthe changing the factors directions dominant are climatic playing of role circumstancesatmospheric an the of parameter of coincides the flood withLittle the summer development. beginning Ice In NAO of Age this the fromcorrelation and transition coe context, 1830 period Modern between onwards Climate is Optimum. conspicuous. Till the This end of the time series, high significant fracture points within thefracture time points series provide indications (according of to changing two-sided the atmospheric flood conditions which development may in a general. Foreland as well as in the Alps in general. However, according to Casty et al. (2005), the the flood frequencies and conditionson of di the atmospheric framework up to today based Subatlantic stage (2.5 ka–present) untilat today. the Despite beginning of the the reduced timefields, availability series temperature of including and the data precipitation absence (until ofbetween 1499), reconstructions climate of significant conditions pressure changes and in floodin the frequencies the can correlation flood be frequencies’ identified. trend Virtually (towards each flood-rich shift or flood-poor periods) coincides with The flood history ofthe the Bavarian beginning Foreland of could behistory the analyzed of 14th in the a century statisticaldocumentary entire onwards way and Bavarian from (based instrumental Foreland data. on was We the could compiled identify existing and statistical data). analyzed, correlations The between based flood on both 6 Discussion the centuries 1500–1599significant ( correlations occurthe (again time-interval verified by by 50 years,1650–1749 the a calculated ( significant persistence). correlationhighly can Shifting significant be observed correlation forthe coef-ficient the relationship of period around 1820between (cf. the Fig. Little 7) Ice coincides Age with and the the important Modern Climate transition Optimum. period accosted. The winter floodpotential occurrences of are the mainlyin relevant alpine in general. catchment terms In areas ofsignificant spite the which correlations of retention supports of thecan the the general development be decline NAO of recognized. of (-index) floods the and In NAO the a importance time first during series step summer, of 100 year summer floods intervals have been considered. For be com-pared fromdominating AD 1500 teleconnection-patterns onwards regulatingclimatic (cf. the Figs. parameters. regional 5 Theclimatic characteristics and NAO seasonal cycle). 7). of also The many reveals NAO seasonal is variationshave one (in been of compared. context The the the confrontation of of comparison the the for annualthe valuables the is general summer depicted in seasonal dominance Fig. in of 5, Fig. summer 7. floods The in particular the importance Bavarian and Foreland were already Is it possiblethe to flood associate historyNAOI (in by of Luterbacher a the etrunning statistical al. mean Bavarian sense) (2002), values) Foreland? the the and time Based of variability series the on of of NAOI the the the (likewise flood 31 reconstruction NAO frequencies year (31 running and of year mean the values) can 5.10.2 Correlations of flood frequencies and NAOI-values in detail 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , ect of ff , V., Macková, J., Müller, M., ň 7428 7427 ek, H.: Historical and Recent Floods in the Czech Republic, š , 2011. , G. 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The − − − − − − s s ff s s s s 3 3 3 3 3 3 79.3 m 16.7 m 972 m 332 m 136 m 191 m cial downstream gauge. ffi 2 2 2 2 2 2 Catchment Area (last access: 23 June 2014), 2014. 160 km 2215 km 135 km 1290 km 220 km 6700 km 250 km260 km520 km 4162 km 8960 km 26 100 km 7432 7431 ∼ ∼ ∼ ∼ ∼ ∼ http://www.zamg.ac.at/cms/de/klima/informationsportal-klimawandel/ Reference data of the Bavarian Foreland rivers, modified after di Etappen, available at: klimavergangenheit/neoklima/lufttemperatur River HeadwatersIller Allgäu High-alps (Germany) Rivers Length Overground Medium Discharge Summer Wertach Allgäu Alps (Germany) Salzach Kitzbühl Alps (Austria) LechIsarInn Rhaetic Alps (Austria) Karwendel Mountains (Austria and Germany) Maloja Saddle (Switzerland) information “Medium Discharge Summer” refers to the lowest o Table 1. Zentralanstalt für Meteorologie und Geodynamik (ZAMG): Lufttemperatur – Entwicklung in Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 7434 7433 Iller Wertach Lech Isar Inn Salzach SummerSpring 42 %Winter 39 % 16 %Autumn 28 20 % % 14 % 57 % 23 % 18 % 58 % 14 % 79 % 12 14 % % 17 % 73 % 12 10 % % 16 % 2 6 % % 9 % 7 % 14 % Research area of the Bavarian Foreland (located between the Alpine Border and the Seasonal distribution of flood events (percentages refer to the individual outer alpine Figure 1. Danube) including the investigated rivers from the northern Limestone Alps. Table 2. river sections) in the Bavarian Foreland for the period 14th century–2008. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | high-pass filtered data. (b) cial records, ffi 7436 7435 Original data from o (a) (b) (a) Monthly maxima of water level (in cm) 1826–1937 at gauge Ettringen/Wertach 31 year running flood frequencies of the Bavarian Foreland. Right ordinate: grey Figure 3. columns show the annual flood frequencies. Figure 2. (a, b) (35 km south of Augsburg). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 7438 7437 test is 2.00 (see red line). Grey bars label flood-rich periods t test estimator of flood frequencies of the Bavarian Foreland, t 31 year running Normalized time series of annual 31 year running flood frequencies in the Bavarian Foreland (blue) andet al., of 2002). Grey annual bars label the 31 year flood-rich periods #3 running to #9 NAOI based on (red) the full-year (NAOI development. data after Luterbacher Figure 5. Figure 4. threshold value for the two-sided #1 to #9. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 7440 7439 Normalized time series of annual 31 year running flood frequencies in the Bavarian Normalized time series of 31 year running flood frequencies in the Bavarian Foreland Figure 7. (blue) and NAOI values (red) foret the al., meteorological summer 2002). (JJA) Grey (NAOI bars data label after Luterbacher the flood-rich periods #3 to #9. Foreland (blue) and “sunspot activity”Hoyt (red) and since Schatten, 1610 1997). Grey (Data barsdevelopment. for label sunspot the activity flood-rich modified periods after #5 to #9 based on the full-year Figure 6.