Sed i men tary re cords of 2010 and 2011 Warta River sea sonal floods in the re gion of Poznañ, Po land
Katarzyna SKOLASIÑSKA1, *, Witold SZCZUCIÑSKI1, Marta MITRÊGA1, Rob ert JAGODZIÑSKI1 and Stanis³aw LORENC1
1 Adam Mickiewicz Uni ver sity in Poznañ, In sti tute of Ge ol ogy, Maków Polnych 16, 61-606 Poznañ, Po land
Skolasiñska, K., Szczuciñski, W., Mitrêga, M., Jagodziñski, R., Lorenc, S., 2015. Sed i men tary re cords of 2010 and 2011 Warta River sea sonal floods in the re gion of Poznañ, Po land. Geo log i cal Quar terly, 59 (1): 47–60, doi: 10.7306/gq.1179 The Warta River near Poznañ (West Po land) rep re sents a me an der ing low land river mod i fied by hy dro-en gi neer ing pro jects.
Re cently, two large floods oc curred dur ing the sum mer of 2010 and the win ter of 2011. Rapid re sponse sur veys were con - ducted to doc u ment ero sion and sed i men tary re cords of the floods (spa tial ex tent, grain size, com po si tion, grain micro - textures). Fol low-up stud ies, which were con ducted dur ing the two years af ter the floods, as sessed postdepositional changes in the flood de pos its. A thick sand layer formed that ranged from an av er age of 10–15 cm (sum mer) to 30–35 cm (win ter), build ing nat u ral lev ees, side bars and cre vasse splays. The sand lay ers con sisted of fine- and me dium-grained sands that were well-sorted, fine skewed and sourced from the river chan nel. The lon ger but smaller win ter flood pro duced thicker and coarser de pos its at dif fer ent sites com pared with the sum mer flood. An or ganic-rich mud layer and al gal mats, which were short-ex ist ing, were also de tected on the floodplain. The study proved that the flood re cord on en gi neered rivers may be only in the sand bod ies near the river chan nel and their pres er va tion is mainly con trolled by their thick ness. A sin gle site may not re cord all floods, as par tic u lar events tend to leave de pos its in var i ous places.
Key words: low land river, flood de pos its, overbank sed i men ta tion, postdepositional changes, Warta River, Cen tral Eu rope.
INTRODUCTION
River floods com prise an im por tant nat u ral haz ard. The as - sess ment of their risk re quires knowl edge of the ex tent and fre - quency of pre vi ous events. This in for ma tion is nec es sary for plan ning flood pro tec tion struc tures, which are usu ally con - structed with the con sid er ation of the larg est flood dur ing the last hun dred or thou sand years. As re corded hu man his tory is usu ally too short to cover these time pe ri ods, sed i men tary ar - chives must be searched to de ter mine the fre quency, du ra tion and ex tent of pre vi ous floods for the as sess ment of flood haz - ards (e.g., Falkowski, 1975; Gonera, 1986; Kalicki, 1996, 2000;
Gêbica and Soko³owski, 2001; Szmañda et al., 2004;
Kaczmarczyk et al., 2008). These geo log i cal re cords are crit i cal to the dis cus sion of in crease in ex treme rain fall re lated to the cli mate change, that gen er ates larger and more fre quent floods (e.g., Milly et al., 2002; Kundzewicz et al., 2010).
The ma jor ity of data on mod ern flood de pos its is de rived from post-flood sur veys; for in stance, sur veys in the Sudety moun tains in Po land (Teisseyre, 1985, 1988; Zieliñski, 2001, 2003), the Parsêta River val ley in Po land (Zwoliñski, 1985,
1992), the river val leys in Ja pan (Iseya, 1989), the Rhine and Meuse River val leys in the Neth er lands (Asselman and Middelkoop, 1995), the Tu ross River in Aus tra lia (Fer gu son and Brierley, 1999), the Dan ube River val ley in Slovakia (Lehotskú et al., 2010), the South Sas katch e wan River val ley in Can ada (Smith and Pérez-Arlucea, 2008; Smith et al., 2010) and the Mis sis sippi River val ley (e.g., Farrell, 1987; Gomez et al., 1997;
Khan et al., 2013). These field in ves ti ga tions of floodplain sed i - men ta tion are ac com pa nied by nu mer ous lab o ra tory ex per i - ments (e.g., Bathurst et al., 2002; Fraselle et al., 2010) and nu - mer i cal mod el ling (e.g., Marriott, 1992). These stud ies show that river flood sed i men ta tion is sig nif i cantly con di tioned by lo - cal fac tors and re mains poorly un der stood. The stud ies of mod - ern flood de pos its also re vealed that these de pos its dif fered from older flood re cords pre served in sed i men tary rock (Brierley et al., 1997; Hud son, 2005). These dif fer ences may be re lated to the ef fects of postdepositional pro cesses, which have not been sub stan tially in ves ti gated (Teisseyre, 1988; Zwoliñski, 1992; Benito et al., 2003; Skolasiñska and Rotnicka, 2011).
Pro longed and tor ren tial rains in May 2010 re sulted in a ma - jor flood that af fected the ma jor ity of the coun tries in cen tral Eu - rope (Bissolli et al., 2011). In Po land, this flood ap peared to be the larg est flood dur ing the last 130 years in the Wis³a River ba - sin (e.g., Zaj¹czkowski et al., 2010; Wierzbicki et al., 2013) and one of the larg est floods in re cent his tory of the Warta River (Fig. 1 and Ta ble 1). Sev eral months af ter this event, the Warta River val ley was flooded again in the win ter of 2010/2011 (Skolasiñska and Rotnicka, 2011). These two floods pro vided the op por tu nity to ex am ine the sedimentological ef fects of ma -
* Corresponding author; e-mail: katskol@amu.edu.pl
Received: May 9, 2014; ac cepted: July 16, 2014; first pub lished on line: July 17, 2014
jor sea sonal floods and the pres er va tion po ten tial of flood de - pos its.
The ma jor ob jec tive of the study is to pres ent doc u men ta - tion of sed i men tary ef fects of two large Warta River floods (June 2010, Jan u ary 2011) in the river val ley near Poznañ (Po - land; Fig. 2A). This sec tion of the Warta River con sists of a nat - u ral floodplain (south of Poznañ) and a por tion in which the course of the river val ley is reg u lated and lim ited by flood em - bank ments (in Poznañ; Fig. 2B). Many low land rivers in Eu rope have been reg u lated for cen tu ries. Thus the study of flood de -
pos its in both nat u ral and en gi neered sys tems are im por tant for the ap pli ca tions of sedimentology in river-flood haz ard as sess - ment (e.g., Klasz et al., 2014).
This study as sesses par tic u larly the two fol low ing is sues:
– if sum mer and win ter floods pro duce vari able sed i men - tary re cords;
– if the sed i men tary re cords of floods are sig nif i cantly al - tered by early postdepositional changes dur ing the two- year post-flood pe riod.
Fig. 1. Pho to graphs of the study area dur ing the floods A to C; ae rial pic tures pre sent ing the max i mum sum mer flood in 2010 (af ter Kaczmarczyk, 2010); note the var i ous ori en ta tions; fields en cir cled with dots de note ap prox i mate lo ca tions
of the sam pling sites, which are rep re sented on Fig ure 2B, C
A – flooded river ter races near Naramowice For est Dis trict; B – flooded area near Lech Bridge; C – in un dated wa ter in take area at Dêbina;
river chan nel is on the right; D1–D3 – the pres ent Warta River val ley near the Naramowice For est Dis trict; the pic tures were taken dur ing D1–
sum mer flood 2010, D2 – win ter flood 2011, and D3 – av er age flow con di tions; the red tri an gles de note the same ori en ta tion points; E1–E3 – pres ent the Warta River val ley near the Lech Bridge; the pic tures were taken dur ing E1 – sum mer flood 2010, E2 – win ter flood 2011, and E3 – av er age flow con di tions; red tri an gles de note the same ori en ta tion points
STUDY AREA
The study was con ducted in the area shaped by the Late Pleis to cene ice sheets – pri mar ily dur ing the Weichselian gla ci - ation. Dur ing the re treat of the last ice sheet, the ma jor land - forms af fect ing the mod ern river val ley were formed. These land forms in clude the War saw-Berlin ice-mar ginal val ley used by the mod ern Warta River in its lat i tu di nal-ori ented course and its north ward-di rected break through part of the river val ley. The lat ter was formed dur ing the Chodzie¿ subphase ap prox i mately 17,200 years BP (Kozarski, 1983, 1991). Stud ies by Bartkowski (1957), Witt (1974), Kozarski (1983), Antczak (1986), Gonera (1986), Kozarski et al. (1988) and Tobolski (1988) re vealed that the Warta River changed from a braided river to a me an der ing river dur ing the late Weichselian.
Cur rently, the Warta River is the third lon gest river in Po land (Fig. 2A). It is a low land me an der ing river with av er age gra di - ents of 0.46‰, and ~0.18‰ near Poznañ (Wiœniewski, 1995).
In the study area, the val ley cuts through ar eas of flat or un du - lat ing mo raine and is pri mar ily filled with Pleis to cene and Ho lo - cene de pos its. In some places, the river chan nel is cut in older clayey sed i ments of the Up per Mio cene and Plio cene age (Bartkowski, 1957; Kozarski et al., 1988).
The study area is lo cated in the mid dle sec tion of the Warta River course (Fig. 2A) from the re gion of Krajkowo in the south to north of Poznañ; it ex tends ap prox i mately 40 km along the course of the Warta (Fig. 2B). In the study sec tion, the Warta val ley var ies from a nat u ral broad val ley (width of ap prox i mately 2 km) in the south (ar eas of Krajkowo and Sowiniec) to a nar row val ley zone (sev eral hun dreds of metres to sev eral doz ens of metres) in the break through sec tion (ar - eas: Dêbina, Lech Bri dge, Naramowice rail way bridge, and Naramowice For est Dis trict).
From the nine teenth cen tury un til the 1970s, the Warta River in Poznañ was sub jected to ar ti fi cial reg u la tions that were
aimed at flood pro tec tion. The banks of the Warta River within the city are cur rently re in forced with con crete slabs, and the val - ley is sur rounded by flood em bank ments. The width and depth of the river in the vi cin ity of Poznañ are de pend ent on the wa ter level and range from 40 to 50 m and from 1.5 to 3.0 m, re spec - tively. The study ar eas of Krajkowo and Dêbina are pro tected due to the ex is tence of the wa ter in take fa cil i ties for the city of Poznañ.
HYDROLOGICAL CHARACTERISTICS OF THE FLOODS IN 2010 AND 2011, AND THE FLOOD
HISTORY IN THE POZNAÑ REGION
High wa ter lev els in the Warta River oc cur sea son ally – usu - ally 1–2 times a year from win ter to spring and/or dur ing the sum mer. The snowmelt floods, which oc cur from March to April, are com mon and rep re sent 80% of all floods dur ing the last 450 years (Kaniecki, 2004). Sum mer floods, which are caused by long-last ing rains, are less fre quent but are usu ally larger than the floods that oc cur dur ing the win ter and spring.
In May 2010, the high est wa ter lev els since 1979 were mea - sured in the val ley of the Warta River in the Poznañ re gion (Ta - ble 1). In 1988, the res er voir “Jeziorsko” was con structed (ap - prox i mately 200-km up stream; Fig. 2A). De spite the con sid er - able dis tance from Poznañ, it has a sig nif i cant im pact on the wa ter lev els and dis charge of the Warta River, par tic u larly dur - ing floods (Miler, 2001). Ac cord ing to un pub lished data from the In sti tute of Me te o rol ogy and Wa ter Man age ment, the 2010 flood in Poznañ be gan on May 10, 2010 with an in crease in wa - ter level from 270 cm (dis charge of 115 m3/s) to 667 cm (dis - charge of 630 m3/s) on June 1, 2010. Thus, the flood per sisted for three weeks (Figs. 1 and 3). The wa ter alarm level (450 cm) was at tained on June 16, 2010 (Fig. 3A).
A few months later, in No vem ber 2010, the next flood oc - curred, which per sisted un til Feb ru ary 2011 (Fig. 3B). The high - est wa ter level of 599 cm was mea sured Jan u ary 22–23, 2011, when a river dis charge of 479 m3/s was at tained. Dur ing the win ter flood, the wa ter lev els and wa ter dis charge were lower than the wa ter lev els and wa ter dis charge dur ing the sum mer flood, whereas the win ter flood lasted lon ger and was char ac ter - ised by three dis tinct flood stages with ris ing and fall ing wa ter lev els (Fig. 3).
METHODS
The geo log i cal im pacts of the 2010 and 2011 floods in the Warta River val ley were as sessed by sur veys that were con - ducted dur ing and im me di ately af ter the floods, when the river wa ter level de creased to an av er age level. A to tal of six sites were in ves ti gated (Fig. 2B, C): A – Naramowice rail way bridge, B – Lech Bridge, C – Krajkowo, D – Dêbina, E – Sowiniec, and F – Naramowice for est dis trict. Sur veys were con ducted in 2010 and 2011 in all six ar eas. In 2012, sur veys were also con ducted at Dêbina; sam ples from the bot tom of the river chan nel were also col lected dur ing the low wa ter level state of the Warta River (25.09.2012).
The sur vey at each site in cluded pho to graphic doc u men ta - tion dur ing and af ter the flood, a re cord of ero sional fea tures, wa ter flow di rec tion in di ca tors, dam age to floodplain in fra struc - ture and the dis tri bu tion of flood sed i men tary de pos its. All fea - tures were mapped us ing GPS (76 sites). In each area, sev eral shal low trenches were dug, doc u mented and sam pled (41 T a b l e 1
Av er age and ex treme wa ter lev els and wa ter dis charges of Warta River in Poznañ
Wa ter level [cm]
Wa ter dis charge [m3/s]
Char ac ter is tic states of the Warta River in Poznañ in pe riod 1946–1990
Ex treme – 26.03.1947 728 1035
Av er age high 484 356
Av er age 268 111
Av er age low 164 41
Low er most – 09.01.1985 93 22.5 Large floods
Af ter the reg u la tion of the river (in 1978 year)
03.1979 700 832
Af ter build ing the stor age res er voir “Jeziorsko” (in 1988 year)
06.2010 667 630
01.2011 599 479
Wa ter level data are for river gauge sta tion (Roch Bridge; Fig. 2B), where 0 cm level is fixed at 49.46 m above sea level, 400 cm is as - signed as a warn ing level and 450 cm is an alarm level. Pre sented data cover pe riod from 1946 to 2012, the av er age val ues are based on pe riod 1961–1990 (data af ter In sti tute of Me te o rol ogy and Wa ter Man age ment; Kaniecki, 2004)
trenches). Sed i ment sam ples for ad di tional anal y sis were col - lected from flood de pos its, un der ly ing soils and river chan nels (208 sam ples – de tails on the sam pling points are pre sented in Ap pen dix 1*). Subsamples col lected for geo chem i cal anal y ses were pre sented by Kozak et al. (2012).
The grain-size dis tri bu tion of all sed i ment sam ples were ob - tained through dry siev ing at 0.5-phi in ter vals. Sam ples with high con tents of fine-grained frac tions were washed on a 4.0 phi sieve. The grain-size sta tis tics were cal cu lated with GRADI - STAT soft ware (Blott and Pye, 2001) by ap ply ing log a rith mic Fig. 2. Study area and sam pling points
A – study area; B – Warta River val ley near Poznañ with 6 iden ti fied test ar eas (in bold); the lo ca tion of the river gauge sta tion and the bor ders of the city of Poznañ (black line) are also marked; C – sketches of the study ar eas with marked po si tions of trenches, sur face sam pling sites and sites in which postdepositional changes were in ves ti gated (ex per i ment sites)
* Supplementary data associated with this article can be found, in the online version, at doi: 10.7306/gq.1179
Folk and Ward graph i cal mea sures (1957). For 35 se lected sam ples, grain-size frac tion that ranged from 1.5–2.0 phi was ana lysed for ma jor com po nents. The iden ti fied quartz, feld - spars, lithic grains, opaque min er als, plant rem nants and shell frag ments were counted un der a bin oc u lar. Five sam ples in the frac tions of 1.0–1.5 phi and 1.5–2.0 phi were ana lysed for the round ness of the quartz grain (an gu lar, in ter me di ate and rounded) and the char ac ter of the grain sur face (shiny or matt) us ing the scale of Cailleux (1942) with mod i fi ca tions of Mycielska-Dowgia³³o and Woronko (1998). Quartz grains in the frac tion 1.0–1.5 phi were se lected from two sam ples and ana - lysed us ing a scan ning elec tron mi cro scope (SEM). The iden ti - fi ca tion of sur face microfeatures in the SEM im ages fol lowed ap proach of Krinsley and Doornkamp (1973) and Mahaney (2002). In three sam ples of mud-al gal mats, or ganic mat ter con tent was de ter mined by the loss on ig ni tion test at 550°C.
The pres er va tion of flood de pos its was mon i tored by re vis it - ing the ma jor ity of the sites that were doc u mented im me di ately af ter the flood, one year af ter the flood and two years af ter the flood. In ad di tion, three test sites were es tab lished in Dêbina in Au gust 2011 (Fig. 2C – points S1, S2, S3), where pre vi ously doc u mented flood de pos its were partly cov ered with a plas tic net (50 x 50 cm) for mon i tor ing changes in sur face sed i ments.
RESULTS
EROSIONAL AND DEPOSITIONAL EFFECTS OF THE FLOODS
The ero sional and depositional forms were doc u mented as the wa ter level de creased, as many of the forms were ephem - eral and could be sub jected to nat u ral re work ing and anthropo - genic res to ra tion ac tions. The re sults are pre sented in Fig ures 4 and 5. As the ef fects of the sum mer and win ter floods were sim i - lar, they are de scribed con cur rently, with the ex cep tion of spe - cific in for ma tion.
EROSION
The ero sional struc tures were iden ti fied only in spe cific places and were com mon for both floods. The most fre quent fea tures were un der cuts of the river banks and the par tial or to - tal de struc tion of the veg e ta tion cover on the river banks. The ob ser va tion of microterraces formed dur ing the grad ual low er - ing of the wa ter level dur ing the late stages of the floods (Fig.
4A) was com mon along the banks. Cre vasses were formed in Fig. 3. Hy dro graphs of (A) the sum mer 2010 and (B) win ter 2011 floods of the Warta River,
as mea sured at the river gauge sta tion (Fig. 2B) Data were pro vided by the In sti tute of Me te o rol ogy and Wa ter
Man age ment – Na tional Re search In sti tute
sev eral places, pri mar ily dur ing the win ter flood. Com mon fea - tures in cluded scours and as so ci ated shadow struc tures, which are re lated to trees (Fig. 4B) and other flow ob sta cles (e.g., wells on the Dêbina wa ter in take). These fea tures were com - mon in the floodplain-prox i mal zone, which ex pe ri enced rapid wa ter flow.
Ero sional fea tures were rare on the grassy ar eas of the floodplains, es pe cially in sum mer, when the grass cover was well-es tab lished. The most fre quent sites for the cre ation of ero - sional niches were ar eas in which pre vi ous earth works had been per formed, e.g., in re la tion to road pro jects and bridge con struc tion (e.g., Lech Bridge, Fig. 4C). Their max i mum depth ex ceeded 0.5 m, and the area ex ceeded 10 m2. In the area of wa ter in take, Dêbina de pres sions sev eral tens of centi metres deep were formed due to suffosion.
DEPOSITION
The most com mon flood sed i ments con sisted of sands.
Their spa tial ex tent was re stricted to a nar row (usu ally 2.5–3 m) zone close to the river chan nel. Sands were de pos ited pri mar ily on well-de vel oped lev ees and on side bars. In the case of cre - vasse splays, which formed when flood wa ter de stroyed the nat u ral lev ees and de pos ited sed i ment on a floodplain, the ex - tent of sandy de pos its reached to a few dozen metres from the river chan nel bank. The thick ness of the sandy de pos its from the sum mer flood ranged from 10 to 15 cm, with a max i mum doc u mented thick ness of 40 cm. Con versely, the win ter flood de pos its were thicker, with an av er age thick ness of 30–35 cm and a max i mum thick ness of 70 cm.
Fig. 4. Sur face depositional and ero sional fea tures af ter the 2010 sum mer flood
A – microterraces on the sandy bank left af ter the wa ter level re ceded (Dêbina); B – de po si tion around trees, in - clud ing scour, shadow struc ture and small cur rent ripplemarks near the bank of the river (Dêbina); C – ero sional scours around the con crete road (Lech Bridge); D – small rip ple marks with crawl ing traces pro duced by bi valves (Dêbina); E – bi valves wan der ing in shal low wa ter on the sandy bot tom of the Warta River (av er age flow con di - tions) and leav ing the same traces as in D (Dêbina) and F – ap prox i mately 1–2 mm thick mud-al gal mat af ter the sum mer flood (Sowiniec); re fer to Fig ure 2B for place names
Sed i men tary struc tures were rarely de tected in the sed i - ments due to the ho mo ge neous min eral com po si tion and good sed i ment sort ing. The most com mon struc tures in cluded climb - ing-rip ple lam i na tion (thick ness of sin gle sets was on av er age 1–2 cm) and mas sive struc tures. On the sed i ment sur face, the most com mon but ephem eral struc tures in cluded small cur rent rip ples (Fig. 4B, D) and mol lusc creep traces (Fig. 4D, E).
Thin lay ers of or ganic-rich muddy de pos its, with a thick ness of a few milli metres, were also fre quently en coun tered. They were clas si fied as muddy sands, as the av er age mud con tent (<4 phi) was 23%. They con tained ap prox i mately 10% or ganic mat ter. These de pos its were pre dom i nantly iden ti fied at a dis - tance of sev eral metres from the chan nel banks. Af ter dry ing, their sur faces were marked with des ic ca tion cracks (Fig. 4F).
Flood de pos its were also ob served in the form of or ganic de - pos its that were com posed of shells and plant de bris. Shell ac cu - mu la tions were de tected in both the prox i mal and the dis tal part of the floodplain. They were com posed of mus sel and snail rem - nants, which were mixed and pre sented as well-pre served spec i - mens (Fig. 5A) and crushed shells. They were lo cated in spe cific ar eas, with a max i mum cov er age of a few square metres. A com - mon form of ac cu mu la tion con sisted of plant de bris (branches and grass), which were fre quently aligned par al lel to the di rec tion of the cur rent flow (Fig. 5B). The plant de bris were fre quently de - pos ited dur ing the ris ing flood wa ter level, as they were of ten cov - ered by sand and pre served in the flood de pos its as lay ers or lenses (Fig. 5C, D). Ex ten sive ar eas of the floodplains had not been cov ered by clastic de pos its. The only depositional ev i dence
Fig. 5. The most com mon or ganic-rich flood de pos its on the floodplain
A – shell lag de pos its af ter the sum mer flood (Dêbina); B – ac cu mu la tion of plant re mains (mainly sticks), which are ori ented par al lel to the flow (Sowiniec); C – layer of sticks likely de pos ited by the ris ing flood wa ter bur ied be - neath sum mer flood sands (Dêbina); D – layer of leaves bur ied be neath win ter flood sands (Sowiniec); E – con - tin u ous al gal mat af ter the sum mer flood (Krajkowo); F – close-up of the mat from E, the mat cov ers pre-flood veg e ta tion (Krajkowo)
of flood ing was a well-de vel oped al gal mat (e.g., Fig. 5E, F). The mats were only ob served for the sum mer flood.
Grain-size dis tri bu tion of flood de pos its. Flood sands, ana lysed in 132 sam ples, ap peared to be very sim i lar in terms of grain-size dis tri bu tion. They were clas si fied as fine- and me - dium-grained sands with a mean grain size in the range of 1.51 to 2.84 phi (av er age 2.19 phi). The coarse frac tion (<0.5 phi) was pri mar ily com posed of shells and plant de tri tus. The sed i - ments were well- to mod er ately well-sorted (stan dard de vi a tion in the range of 0.27–0.61 phi). The skew ness ranged from –0.07 to 0.39, there fore the grain-size dis tri bu tions were sym - met ri cal, fine-skewed and very-fine-skewed. The kurtosis ranged from 0.86 to 1.5; thus, the most com mon type of dis tri -
bu tion was platykurtic, but mesokurtic and leptokurtic dis tri bu - tions were also rep re sented.
Muddy or ganic mats, which were ana lysed in 3 sam ples, were com posed of fine and very fine sands that were poorly sorted (av er age stan dard de vi a tion: 1.83 phi) with an av er age mean grain size of 3.27 phi. Frac tions <2 phi were pri mar ily com posed of plant detritus.
When di vided into sed i ments from lev ees, cre vasse splays, other prox i mal floodplain forms, and dis tal floodplains, only the lat ter dif fered in terms of grain size (Fig. 6A). They were finer and poorly sorted. The com par i son of de pos its from the win ter and sum mer floods re vealed that the win ter flood sands tended to be coarser and better sorted (Fig. 6B).
Fig. 6. Plots of mean grain size ver sus sort ing for A – flood de pos its from lev ees (LV), cre vasse splays (CS), other prox i mal floodplain forms (PF), and dis tal floodplain (DF); B – flood sands clas si fied as 2010 sum mer flood de - pos its (sum mer), the 2011 win ter flood de pos its (win ter) and older sandy river de pos its and C – all ana lysed sam - ples clas si fied into flood sands (Sf), mud-al gal mats (M), pre-flood soils or or ganic-dom i nated sed i ments (O) and anthropogenic sands re de pos ited dur ing the flood (Sa)
Fig. 7. Com par i son of the sandy flood-de pos its and mod ern Warta River chan nel de pos its (col lected dur ing low-wa ter dis charge sea son near the flood im pact sites)
Re la tion of grain-size sta tis tics in sandy river sed i ments and trends in re la tions be tween grain-size pa ram e ters for flu vial sed i ments (1 – river chan nel sed i ments, 2 – overbank sed i ments) con sid ered to be typ i cal
for flu vial de pos its (af ter Mycielska-Dowgia³³o and Ludwikowska-Kêdzia, 2011)
Grain-size dis tri bu tion of non-flood de pos its. The soils and or ganic mat ter-rich sed i ments and anthropogenic sands (de liv ered dur ing earth works and re de pos ited dur ing overbank flow) were ana lysed in 19 and 11 sam ples, re spec tively. They were dis tinctly dif fer ent in terms of grain size sta tis tics from the flood de pos its (Fig. 6C). They cov ered an ex ten sive range of grain sizes (from fine sand to me dium sand) com pared with flood de pos its and were char ac ter ised by mod er ate to poor sort ing.
The range of grain size sta tis tics for the river chan nel de - pos its ana lysed in 43 sam ples fell within the range of flood sands (Fig. 7). How ever, the sandy de pos its from floods tended to re veal the best sort ing in the range of the fin est frac tions, whereas the sam ples from the river chan nel re vealed that the coarser frac tions were the best sorted. The flood de pos its were mainly fine skewed, whereas the grain-size dis tri bu tions of the river chan nel de pos its tended to be sym met ri cal. The re la tion - ship be tween the mean grain size and the skewness of the flood de pos its re vealed a char ac ter is tic “zig-zag” pat tern, whereas the river chan nel de pos its tended to be char ac ter ized by more fine-skewed dis tri bu tions in the sed i ments with a finer mean grain size (Fig. 7).
COMPOSITION OF FLOOD SANDS
The flood sands dis played a sim i lar com po si tion. They were dom i nated by quartz (88.5% on av er age), plant rem nants (3.5%), lithic grains (3.5%), feld spars (2.5%), opaque min er als (1.5%) and shell frag ments (0.5%). Plant frag ments and shell rem nants were only pres ent in some sam ples; the re main ing
com po nents were pres ent in all sam ples in sim i lar amounts.
The sam ples from the sum mer and win ter floods do not show sig nif i cant dif fer ences.
ROUNDNESS AND MICROMORPHOLOGY OF QUARTZ GRAINS
In terms of grain round ness and sur face char ac ter, the most com mon grains in the flood sands were clas si fied as fol lows: in - ter me di ate-shiny sur face (55%), in ter me di ate-matt sur face (32%), an gu lar (10%), round-shiny sur face (1.5%) and round- matt surface (1.5%).
The grains from in ter me di ate-shiny and round-shiny classes (Fig. 8A) were ana lysed with SEM (Fig. 8B). A com mon sur face fea ture was chem i cal etch ing, as shown by the micro - structure of the dulled sur face (smooth pol ished sur face) and the dis so lu tion sur face (rough), par tic u larly in a microde - pression (Fig. 8C). Only a few struc tures were pro duced by me - chan i cal abra sion, such as sin gle v-shaped per cus sion cracks (Fig. 8D), conchoidal frac tures (Fig. 8E) and subparallel lin ear frac tures. How ever, they were al tered by the chem i cal weath e r - ing pro cesses.
POSTDEPOSITIONAL CHANGES
The vast ar eas of floodplains were cov ered by al gal mats dur ing the sum mer flood, par tic u larly at Krajkowo and Sowiniec (Fig. 5E, F), where they were of ten the only depositional ef fect
Fig. 8. Typ i cal microfeatures of quartz grains in the 0.35–0.5 mm frac tion
A – dom i nat ing pol ished and subrounded quartz grains; B – an ex am ple of rounded and pol ished quartz grain in SEM; C – ex am ple of grain sur face with v-shaped per cus sion cracks (vp) and dulled sur face (dl); D – ex am ple of grain sur face with a dis so lu tion
sur face (ds) and a dulled sur face; E – ex am ple of grain sur face with conchoidal frac tures (cf)
Fig. 9. Postdepositional his tory of the flood de pos its in mon i tor ing sites es tab lished in the Dêbina wa ter in take area (Fig. 2C)
The mon i tor ing plots were partly cov ered by plas tic nets to dis tin guish post-flood ma te rial; the sur face sed i ments at sites S1-1, S1-2 and S2-1 are pre sented for the pe riod im me di ately af ter the flood, 4 months af ter the flood, 7 months af ter the flood and 13 months af ter the
flood; af ter 13 months, shal low pits were dug to ver ify the pres er va tion of the flood de pos its (last se ries of pic tures)
of the flood. Af ter the floodplains dried, the mats re mained for ap prox i mately one month; they were sub se quently in ter sected by grow ing veg e ta tion and de com posed.
The sandy flood de pos its were well-pre served; how ever, the sur face struc tures and up per parts of the de pos its were rap - idly re worked with lit tle po ten tial to be re corded in fos sil flood de pos its. The trans for ma tion of sed i ments was at trib uted to two pe ri ods: with out cover veg e ta tion (dom i nated by wind, rain, and hu man and an i mal ac tiv i ties) and af ter colo nis ation with plants (dom i nated by soil-form ing pro cesses). Among the ob served ef fects as so ci ated with the first pe riod, the most im por tant ef - fects were the redeposition of sand by wind, rain blur ring, traces of liv ing an i mals and hu mans (in clud ing traces of car wheels).
In ten sive wind trans port ob served dur ing the field works con - trib uted to the rapid trans for ma tion of flu vial forms of de po si tion into new forms – dunes with char ac ter is tic large-scale cross strat i fi ca tion and with a max i mum height of sev eral tens of centi metres. Rapid colo nis ation by veg e ta tion (mainly grass) oc curred in priv i leged places (days to weeks). How ever, in the case of thick sandy de pos its, plant re cov ery was much slower (af ter two years, the sand was not cov ered by con tin u ous veg e - ta tion). To doc u ment the rate of change, three ex per i ments on con trol plots that were partly cov ered with mesh were con - ducted (Fig. 9). Nine teen months af ter the win ter flood, the mesh was cov ered with liv ing grass and plant de bris (leaves and stems) in all places. In the case of a new flood, they may serve as a clear interflood layer.
The thick ness is most likely the most im por tant fac tor for the pres er va tion of the de pos its, as the sev eral centi metre thick flood de pos its were well-pre served af ter two years. At sites cov - ered by thin ner sand de pos its or muddy sand de pos its, the rec - og ni tion of par tic u lar flood de pos its af ter one veg e ta tion season was hardly possible.
DISCUSSION
THE SEDIMENTARY FLOOD RECORD IN THE WARTA RIVER VALLEY
Floodplain de po si tion is pri mar ily lim ited to the clos est prox - im ity of the river chan nel (<2.5–3.0 m) within the lev ees of the Warta River and is likely due to a nearly straight course that is ar ti fi cially reg u lated. Al though the ex tent of river flood ing was rel a tively sig nif i cant – in ex cess of 1 km – the wa ter flow and sed i ment trans port in the di rec tion per pen dic u lar to the river chan nel banks is con sid ered to be small for rivers with a rel a - tively straight course (James, 1985; Bathurst et al., 2002). Con - se quently, the dis per sion of sed i ments is small and the sands pre dom i nantly pro duce lev ees. Their for ma tion is likely re lated to tur bu lent ed dies, which are re spon si ble for sed i ment lift ing and trans fer ring from the chan nel to the near chan nel-bank zone. This mech a nism of sand trans port is de fined as the tur bu - lent dif fu sion of sus pended ma te rial (Pizzuto, 1987; Marriott, 1992; Asselman and Middelkoop, 1995) and pro duces rel a - tively thick sand ac cu mu la tion close to the chan nel.
The in ves ti gated floods de pos ited lit tle sed i ments from sus - pen sion (muds), al though they are con sid ered to be typ i cal of floods. The lim ited sus pen sion load in the trans port and the hy - drau lic char ac ter of the flood wa ters in the straight course of the river are pos si ble causes (Bathurst et al., 2002). The Warta River is a typ i cal low land river with a small slope and rel a tively flat catch ment area. These fac tors may limit the de liv ery of fine-grained sed i ments from the catch ment. The sed i ments
from the up per course of the river are stored in the “Jeziorsko
res er voir. The straight course of the river through the south- north ori ented break through part of the val ley is po ten tially a trans fer zone for sus pen sion load, which is likely to be de pos - ited in the parts of the val ley with slower wa ter flow.
The ac cu mu la tions of large num ber of well-pre served snail shells (Fig. 5A) in some lim ited parts of floodplain may be re - lated to mi gra tion of the snails dur ing the sum mer flood from the chan nel mar gin to ward the floodplain be cause of food avail abil - ity (Tatsuaki Nakato, pers. comm., 2014). Rapid change of the con di tions dur ing re ces sion of flood wa ters could cause that they could not fol low and died out leav ing a dis con tin u ous layer of shells.
Floodplains are fre quently char ac ter ized by sig nif i cant lo cal vari abil ity in sed i men ta tion (Asselman and Middelkoop, 1995), which is con firmed by the re sults of this study. For ex am ple, the win ter and sum mer floods pro duced de pos its in var i ous ar eas and amounts. The ma jor depositional ar eas of the sum mer flood were not af fected by the win ter flood. As con sec u tive floods may pro duce de pos its in dif fer ent places, the sed i men - tary re cord of floods from a sin gle site is likely to be in com plete.
Sim i lar ob ser va tions were ob tained by Lehotský et al. (2010).
They found that depositional ef fects of the flood ing of the Dan - ube River in Bratislava from 2002–2007 were dif fer ent in terms of the amount of ac cu mu lated sed i ment, sed i ment tex ture and spa tial dis tri bu tion.
FLOOD HYDRODYNAMICS – INSIGHTS FROM PROPERTIES OF FLOOD DEPOSITS
Sed i ment prop er ties are com monly used to de ci pher hy dro - dy namic (e.g., palaeoflow) con di tions dur ing their de po si tion.
To es ti mate the wa ter flow re gime dur ing the ac cu mu la tion of lev ees, we used a di a gram by Sly et al. (1983) that dis crim i - nates the lower and up per flow re gime de pend ing on the skew - ness and the kurtosis. The de pos its of the lev ees formed dur ing the stud ied floods cor re spond to the con di tions of the lower flow re gime. These flow con di tions are also con firmed by the ob - served sed i men tary struc tures, e.g., small-scale rip ple strat i fi - ca tion (Singh, 1972).
Wa ter flow ve loc ity was also es ti mated us ing the me dian value of the sam ples from the lev ees, which is 0.22 mm, and us - ing the model of Miller et al. (1977). This model as sumes one-di rec tional flow con di tions, pro vides the ve loc ity at a depth of 100 cm above the bed and is ded i cated to sed i ments that are pri mar ily com posed of quartz and feld spars. The cal cu lated ve - loc ity is 0.4 m/s, which cor re sponds with the ob served wa ter ve - loc i ties dur ing the sum mer flood. The max i mum ve loc i ties, which were mea sured next to the river gauge sta tion (Fig. 2B), were 1.9 m/s in the main river chan nel and 0.5 m/s on the floodplain (data ac cord ing to the In sti tute of Me te o rol ogy and Wa ter Man age ment – Na tional Re search In sti tute).
The sed i ment prop er ties also pro vided in sight into the de po - si tion mech a nism, e.g., from the bedload or graded sus pen sion.
For sandy flood de pos its (es pe cially lev ees), a dis tinct in crease in the av er age grain size with sort ing was ob served. This trend is com mon in overbank river sed i ments (Mycielska-Dowgia³³o, 1995; Kaczmarczyk et al., 2008; Mycielska-Dowgia³³o and Ludwikowska-Kêdzia, 2011; Szmañda, 2011). Dur ing the flood, sort ing pro cesses pre vail within the coarser frac tions, and the finer ma te rial that is de pos ited from sus pen sion is less sorted and en riched in the fine-grained frac tion, which re sults in fine- skewed grain size dis tri bu tions.
Grain fea tures pro vide in for ma tion about sed i ment sources and trans port mech a nism. The sim i lar ity of the grain size dis tri - bu tions of flood de pos its and the river chan nel sed i ments in di - cates a short overbank trans port. The sim i lar ity also sug gests the lim ited con tri bu tion of ex ter nal sed i ment sources. The SEM stud ies show that the flood de pos its con sist of mul ti ple times re - worked river sed i ments. The smooth sur face of the grains – dulled sur face – was caused by the dis so lu tion of the sur face and the si mul ta neous trans port in an aque ous en vi ron ment.
These grain fea tures are in ter preted by Woronko and Ostro - wska (2009) as com mon fea tures of a flu vial en vi ron ment in con di tions in which the river re works the older flu vial sed i ments.
A con fir ma tion of the in ter pre ta tion that the flood de pos its pri - mar ily orig i nate from the river chan nel is the pres ence of bi - valves and snails. Alexandrowicz (1998) dem on strated shell ac cu mu la tions de pos ited dur ing floods on the floodplain, re fle - ct ing the short trans port from the bot tom of the river in stead of the ad ja cent ar eas.
DIFFERENCES IN THE SEASONAL FLOOD RECORDS
The sum mer and win ter floods dif fer with re gards to spa tial dis tri bu tion of the ac cu mu la tion sites, the amount of sed i ments and their grain size. The win ter flood de pos ited sands in a greater num ber of places, and the flood de pos its were thicker.
These de pos its were coarser. Sev eral po ten tial rea sons ex - plain these dif fer ences; the win ter flood was lon ger but the tem - per a ture and plant cov er age may also be the fac tors. The tem - per a ture of the win ter river-wa ter is a few cen ti grade, close to the tem per a ture for the max i mum wa ter den sity, thus wa ter vis - cos ity is rel a tively high. These con di tions en able a larger amount of ma te rial to be trans ported by the river com pared with con di tions dur ing the sum mer. Dur ing the sum mer, the wa ter flow on the floodplains is re stricted by grow ing plants, and the sed i ment/soils are well-sta bi lised by grow ing roots. On con - trary, dur ing the win ter, as also ob served dur ing the case study, the abil ity to gen er ate cre vasses in creases (Teisseyre, 1985).
How ever, the com po si tion of the flood de pos its and the grain round ness and sur face fea tures do not dif fer be tween the sum - mer and win ter floods.
THE PRESERVATION POTENTIAL OF FLOOD DEPOSITS
In the tem per ate cli mate zone, where the floodplains are pre dom i nantly over grown with veg e ta tion, the postdepositional trans for ma tion of mod ern flood de pos its oc curs rap idly (they be gin im me di ately af ter the flood wa ter re cedes). Our two-year
ob ser va tion re vealed that thin muddy and sandy de pos its were not likely to be pre served in a geo log i cal re cord. Thicker de pos - its may be pre served and are rap idly cov ered by a new or - ganic-rich soil ho ri zon, en abling their iden ti fi ca tion. Our ob ser - va tions are con sis tent with the con clu sions of Teisseyre (1988).
He con ducted stud ies of the rivers in south ern Po land for three years and de ter mined that all mud de pos its were re worked to var i ous ex tents and were in cluded in the soil pro file.
CONCLUSIONS
This study doc u mented the ef fects of two rel a tively large floods (sum mer 2010 and win ter 2011) on a rel a tively straight, partly reg u lated, me an der ing river in a tem per ate cli ma tic zone.
The de po si tion dur ing the floods only fo cused on the near river chan nel zone, which was dom i nated by lay ers of sands with a max i mum thick ness of 70 cm. Al most no de po si tion was de - tected on the ma jor ity of the floodplain. The com po si tion of the two floods re vealed that they dif fered in the sedimentological re - cord. Dur ing the win ter flood (lon ger du ra tion but with a slightly smaller mag ni tude than the sum mer flood) more sed i ment was de pos ited along the chan nel banks, and the de pos ited sed i - ments were slightly coarser. As the depositional ar eas of both floods dif fered, po ten tial palaeoflood re con struc tions must con - sider the spa tial depositional vari abil ity. The de po si tion oc curred in a low en ergy re gime with a re con structed wa ter flow ve loc ity of 0.4 m/s, which was sim i lar to the ac tual mea sured ve loc i ties. The flood de pos its of a low land river in a tem per ate cli mate, in which the floodplain is cov ered with veg e ta tion, are rap idly sub jected to colo nis ation by veg e ta tion, which blurs the shape of forms and pri mary depositional fea tures of sed i men tary de pos its. In this case, de pos its must be at least sev eral centi metres thick to be pre served. The postdepositional al ter na tions of thin ner de pos its cause their ef fec tive re moval within a sin gle year.
Ac knowl edge ments. This study was sup ported by the Min is try of Sci ence and Higher Ed u ca tion, grant No. NN 304 105240. The au thors are grate ful to the Aquanet S.A. Com pany for ac cess and per mis sion to con duct re search in the wa ter in - take area. The In sti tute of Me te o rol ogy and Wa ter Man age ment – Na tional Re search In sti tute kindly pro vided data on wa ter lev els, dis charges and flow ve loc ity of the Warta River for 2010 and 2011. We ac knowl edge D. Kasztelan who as sisted with the doc u men ta tion map and A. Rojewska for her col lab o ra tion dur - ing the SEM anal y ses. We thank J. Przyby³ek and T. Zieliñski for their dis cus sion about the re sults. Com ments from re view - ers T. Kalicki and T. Nakato helped us to im prove the manu - script and we grate fully ac knowl edge their ef forts. We would also like to thank T.M. Peryt and W. Granoszewski for ed i to rial sup port.
REFERENCES
Alexandrowicz, S.W., 1998. Thanatocoenoses of molluscs from flood de pos its in Imbramowice near Cra cow (in Pol ish with Eng - lish sum mary). Dokumentacja Geograficzna, 11: 69-83.
Antczak, B., 1986. Chan nel pat tern con ver sion and ces sa tion of the Warta River bi fur ca tion in the War saw-Berlin pradolina and the
south ern Poznañ gap sec tion dur ing the Late Vistulian (in Pol ish with Eng lish sum mary). Zeszyty Naukowe UAM Poznañ, seria Geografia, 35.
Asselman, N.E.M., Middelkoop, H., 1995. Floodplain sed i men ta - tion: quan ti ties, pat terns and pro cesses. Earth Sur face Pro - cesses and Land forms, 20: 481–499.
Bartkowski, T., 1957. Die Entwicklung des postglazialen Entwässer gungssystem im mittleren Grosspolen (in Pol ish with Ger man sum mary). Zeszyty Naukowe UAM Poznañ, seria Geografia, 1: 3–79.
Bathurst, J.C., Benson, I.A., Val en tine, E.M., Nalluri, C., 2002.
Overbank sed i ment de po si tion pat terns for straight and me an - der ing flume chan nels. Earth Sur face Pro cesses and Land - forms, 27: 659–665.
Benito, G., Sánchez-Moya, Y., SopeÔa, A., 2003. Sedimentology of high-stage flood de pos its of the Targus River, Cen tral Spain.
Sed i men tary Ge ol ogy, 157: 107–132.
Bissolli, P., Friedrich, K., Rapp, J., Ziese, M., 2011. Flood ing in east ern cen tral Eu rope in May 2010 – rea sons, evo lu tion and cli - ma to log i cal as sess ment. Weather, 66: 147–153.
Blott, S.J., Pye, K., 2001. Gradistat: a grain size dis tri bu tion and sta tis tics pack age for the anal y sis of un con sol i dated sed i ments.
Earth Sur face Pro cesses and Land forms, 26: 1237–1248.
Brierley, G.J., Fer gu son, R.J., Woolfe, K.J., 1997. What is a flu vial levee? Sed i men tary Ge ol ogy, 114: 1–9.
Cailleux, A., 1942. Les ac tions éoliennes périglaciaires en Eu rope.
Société géologique de France, Memoire, 41.
Falkowski, E., 1975. Vari abil ity of chan nel pro cesses of low land rivers in Po land and changes of the val ley floors dur ing the Ho lo - cene. Biuletyn Geologiczny, 19: 45–78.
Farrell, K.M., 1987. Sedimentology and fa cies ar chi tec ture of over - bank de pos its of the Mis sis sippi River, False River re gion, Lou i - si ana. Jour nal of Sed i men tary Pe trol ogy, 57: 111–120.
Fer gu son, R.J., Brierley, G.J., 1999. Levee mor phol ogy and sedimentology along the lower Tu ross River, south-east ern Aus tra lia. Sedimentology, 46: 627–648.
Folk, R.L., Ward, W.C., 1957. Brazos River bar: a study in the sig nif - i cance of grain size pa ram e ters. Jour nal of Sed i men tary Pe trol - ogy, 27: 3–26.
Fraselle, Q., Bousmar, D., Zech, Y., 2010. Ex per i men tal in ves ti ga - tion of sed i ment de po si tion on floodplains. In: Pro ceed ings of the River Flow 2010 Con fer ence, Vol. 1 (eds. A. Dittrich, J. Koll, J. Aberle and P. Geisenhainer): 823–830.
Gêbica, P., Soko³owski, T., 2001. Sedimentological in ter pre ta tion of cre vasse splays formed dur ing the ex treme 1997 flood in the up per Vistula river val ley (South Po land). Annales Societatis Geologorum Poloniae, 71: 53–62.
Gomez, B., Phillips, J.D., Magilligan, F.J., James, L.A., 1997.
Floodplain sed i men ta tion and sen si tiv ity: sum mer 1993 flood, up per Mis sis sippi River val ley. Earth Sur face Pro cesses and Land forms, 22: 923–936.
Gonera, P., 1986. Changes in ge om e try of the Warta me an der ing chan nels against cli ma tic fluc tu a tions dur ing the Late Vistulian and Ho lo cene (in Pol ish with Eng lish sum mary). Wyd. Naukowe UAM Poznañ, seria Geografia, 33.
Hud son, P.F., 2005. Nat u ral Lev ees. In: En cy clo pe dia of Wa ter Sci - ences. Tay lor & Fran cis.
Iseya, F., 1989. Mech a nism of in verse grad ing of sus pended load de pos its. In: Sed i men tary Fa cies in the Ac tive Plate Mar gin (eds. A. Taira and F. Masuda): 113–129.
James, C.S., 1985. Sed i ment trans port to overbank sec tion. Jour - nal of Hy drau lic Re search, 23: 435–452.
Kaczmarczyk, M., 2010. http://www.city.poznan.pl/mapa_geopoz/
data/wizua lizacja/in dex.php?scie zka=../wizualizacja/powo - dz_2010/, July 2014.
Kaczmarczyk, J., Florek, W., Olszak, I.J., 2008. Late Ho lo cene and re cent land forms and floodplain de pos its in the mid dle Wieprza val ley (in Pol ish with Eng lish sum mary). Landform Anal y sis, 7: 80–94.
Kalicki, T., 1996. Overbank de pos its as in di ca tor of the changes in dis charges and sup ply of sed i ments in the up per Vistula val ley – the role of cli mate and hu man im pact. Geo graph ical Stud ies, 9:
43–60.
Kalicki, T., 2000. Grain size of the overbank de pos its as car ries of paleogeographical in for ma tion. Qua ter nary In ter na tional, 72:
107–114.
Kaniecki, A., 2004. Poznañ – the His tory of the City Writ ten with Wa ter (in Pol ish with Eng lish sum mary). Pub lish ing House of the Poznañ So ci ety for the Ad vance ment of the Arts and Sci ences.
Khan, N.S., Hor ton, B.P., McKee, K.L., Jerolmack, D., Falcini, F., Enache, M.D., Vane, C.H., 2013. Track ing sed i men ta tion from the his toric A.D. 2011 Mis sis sippi River flood in the deltaic wetlands of Lou i si ana, USA. Ge ol ogy, 41: 391–394.
Klasz, G., Reckendorfer, W., Ga briel, H., Baumgartner, C., Schmal fuss, R., Gutknecht, D., 2014. Nat u ral levee for ma tion along a large and reg u lated river: the Dan ube in the Na tional Park Donau-Auden, Aus tria. Geo mor phol ogy, 215: 20–33.
Krinsley, D., Doornkamp, J.C., 1973. At las of Sand Grain Sur face Tex tures. Cam bridge Uni ver sity Press, Cam bridge.
Kozak, L., Skolasiñska, K., Niedzielski, P., 2012. En vi ron men tal im pact of flood: the study of ar senic speciation in ex change able frac tion of flood de pos its of Warta river (Po land) in de ter mi na - tion of ‘‘fin ger prints’’ of the pol lut ants or i gin and the ways of the mi gra tion. Chemosphere, 89: 257–261.
Kozarski, S., 1983. River chan nel changes in the mid dle reach of the Warta Val ley, Great Po land, Low land. Qua ter nary Stud ies in Po land, 4: 159–169.
Kozarski, S., 1991. Warta – a case study of low land river. In: Tem - plate Paleohydrology (eds. L. Starkel, K.J. Greg ory and J.B.
Thornes): 189–215. John Wiley and Sons, Chichester, UK.
Kozarski, S., Gonera, P., Antczak, B., 1988. Val ley floor de vel op - ment and paleohydrological changes: the Late Vistulian and Ho - lo cene his tory of the Warta river (Po land). In: Lake, Mire and River En vi ron ments Dur ing the Last 15000 Years (eds. G. Lang and C. Schluchter): 185–203. Balkema, Rot ter dam.
Kundzewicz, Z.W., Lugeri, N., Dankers, R., Hirabayashi, Y., Doell, P., Pinskwar, I., Dysarz, T., Hochrainer, S., Matczak, P., 2010. As sess ing river flood risk and ad ap ta tion in Eu rope – re - view of pro jec tions for the fu ture. Mit i ga tion and Ad ap ta tion Strat e gies for Global Change, 15: 641–656.
Lehotský, M., Novotný, J., Szmañda, J.B., 2010. Re sponse of the Dan ube River floodplain to flood events dur ing 2002–2007 pe - riod. Quaestiones Geographicae, 29: 37–45.
Mahaney, W.C., 2002. At las of Sand Grain Sur face Tex tures and Ap pli ca tions. Ox ford Uni ver sity Press.
Marriott, S., 1992. Tex tural anal y sis and mod el ing of a flood de - posit: River Severn, U.K. Earth Sur face Pro cesses and Land - forms, 17: 687–697.
Miler, A.T., 2001. In flu ence of the Jeziorsko res er voir on the Warta River dis charges at the Poznañ (in Pol ish with Eng lish sum mary).
Kompleksowe i szczegó³owe problemy in¿ynierii œrodowiska, Sci en tific Con fer ence in Ustronie Morskie: 735–743.
Miller, M.C., McCave, I.N., Komar, P.D., 1977. Thresh old of sed i - ment mo tion un der uni di rec tional cur rents. Sedimentology, 24:
507–527.
Milly, P.C.D., Wetherald, R.T., Dunne, K.A., Delworth, T.L., 2002.
In creas ing risk of great floods in a chang ing cli mate. Na ture, 415: 514–517.
Mycielska-Dowgia³³o, E., 1995. Se lected tex tural fea tures of de - pos its and their in ter pre ta tion value (in Pol ish with Eng lish sum - mary). In: Badania osadów czwartorzêdowych. Wybrane metody i interpretacja wyników (eds. E. Mycielska-Dowgia³³o and J. Rutkowski), Warszawa: 29–105.
Mycielska-Dowgia³³o, E., Ludwikowska-Kêdzia, M., 2011. Al ter - na tive in ter pre ta tions of grain-size data from Qua ter nary de pos - its. Geologos, 17: 189–203.
Mycielska-Dowgia³³o, E., Woronko, B., 1998. Round ing and frost - ing anal y sis of quartz grains of sand frac tion, and its in ter pre tive value (in Pol ish with Eng lish sum mary). Przegl¹d Geologiczny 46: 1275–1281.
Pizzuto, J., 1987. Sed i ment dif fu sion dur ing overbank flows.
Sedimen tology, 34: 301–317.
Singh, I.B., 1972. On the bed ding in the nat u ral-levee and the point bar de pos its of the Gomti River, Uttar Pradesh, In dia. Sed i men - tary Ge ol ogy, 7: 309–317.
Skolasiñska, K., Rotnicka, J., 2011. Pozakorytowe osady Warty zdeponowane w czasie powodzi zimowej 2010/2011 na zakolu rzeki w Marlewie (Poznañ S) (in Pol ish). In: Varia. Prace z zakresu geografii i geologii (eds. J. Biernacka and J. Kijowska):
7–25. Bogucki Wydawnictwo Naukowe, Poznañ.
Sly, P.G., Thomas, R.L., Pelletier, B.R., 1983. In ter pre ta tion of mo - ment mea sures de rived from wa ter-lain sed i ments. Sedimen - tology, 30: 219–233.
Smith, G.H.S., Best, J.L., Ashworth, P.J., Lane, S.N., Parker, N.O., Lunt, I.A., Thomas, R.E., Simpson, C.J., 2010. Can we dis tin guish flood fre quency and mag ni tude in the sedimen - tological re cord of rivers? Ge ol ogy, 38: 579–582.
Smith, N.D., Pérez-Arlucea, M., 2008. Nat u ral levee de po si tion dur ing the 2005 flood of the Sas katch e wan River. Geo mor phol - ogy, 101: 583–594.
Szmañda, J., 2011. Re cord of depositional con di tions in grain size com po si tion of overbank de pos its (in Pol ish with Eng lish sum - mary). Landform Anal y sis, 18.
Szmañda, J., Oczkowski, H., Przegiêtka, K., 2004. Age of the Vistula river overbank de pos its in Toruñ. Geochronometria, 23:
35–38.
Teisseyre, A.K., 1985. Re cent overbank de pos its of the Sudetic val - leys, SW Po land. Part I: Gen eral en vi ron men tal char ac ter is tics (with ex am ples from the up per river Bóbr drain age ba sin (in Pol - ish with Eng lish sum mary). Geologica Sudetica, 20: 113–195.
Teisseyre, A.K., 1988. Re cent overbank de pos its of the Sudetic val leys, SW Po land. Part III: Subaerially and subaqueously de - pos ited overbank sed i ments in the light of field ex per i ment (1977-1979) (in Pol ish with Eng lish sum mary). Geologia Sude - tica, 23: 1–55.
Tobolski, K., 1988. Paleobotanical study of BØlling sed i ments of
¯abinko in the vi cin ity of Poznañ, Po land. Quaestiones Geo - graphicae, 10: 119–124.
Wierzbicki, G., Ostrowski, P., Mazgajski, M., Bujakowski, F., 2013. Us ing VHR multispectral re mote sens ing and LIDAR data to de ter mine the geomorphological ef fects of overbank flow on a floodplain (the Vistula River, Po land). Geo mor phol ogy, 183:
73–81.
Wiœniewski, J., 1995. Przebudowa poznañskiego wêz³a wodnego zabezpieczeniem przed powodzi¹ Poznania (in Pol ish). In:
Wody powierzchniowe Poznania, problemy wodne obszarów miejskich (eds. A. Kaniecki and J. Rotnicka): 224–233. Sci en - tific Con fer ence in Poznañ.
Witt, A., 1974. Re con struc tion of di rec tion of Warta out flow in the high est ter race level of gap of the Warta val ley near Poznañ (in Pol ish with Eng lish sum mary). Badania Fizjograficzne nad Polsk¹ Zachodni¹, seria Geografia Fizyczna, 27: 179–208.
Woronko, B., Ostrowska, M., 2009. The in flu ence of flu vial en vi - ron ment on the char ac ter of quartz grain sur face – a dis cus sion (in Pol ish with Eng lish sum mary). Geneza, litologia i stratygrafia utworów czwartorzêdowych, 5, seria Geografia, 88: 607–625.
Zaj¹czkowski, M., Darecki, M., Szczuciñski, W., 2010. Re port on the de vel op ment of the Vistula River plume in the coastal wa ters of the Gulf of Gdañsk dur ing the May 2010 flood. Oceanologia, 52: 311–317.
Zieliñski, T., 2001. Ero sional ef fects of cat a strophic flood in the Nysa Klodzka drain age ba sin dur ing the 1997 and 1998 events, SW Po land (in Pol ish with Eng lish sum mary). Przegl¹d Geolo - giczny, 49: 1096–1100.
Zieliñski, T., 2003. Cat a strophic flood ef fects in al pine/foot hill flu vial sys tem (a case study from the Sudetes Mts, SW Po land). Geo - mor phol ogy, 54: 293–306.
Zwoliñski, Z., 1985. Sed i men ta tion ver ti cal ac cre tion of sed i ments on the Parsêta river floodplain (in Pol ish with Eng lish sum mary).
Badania Fizjograficzne nad Polsk¹ Zachodni¹, 35 (A): 205–238.
Zwoliñski, Z., 1992. Sedimentology and geo mor phol ogy of over - bank flows on me an der ing river floodplains. Geo mor phol ogy, 4:
367–379.
