10.2478/v10060-008-0068-4

Annals of Warsaw University of Life Sciences – SGGW Land Reclamation No 42 (1), 2010: 93–104 (Ann. Warsaw Univ. of Life Sci. – SGGW, Land Reclam. 42 (1), 2010)

Basement of the alluvia infl uence on the channel pattern in example of selected reach of the Pilica River

TOMASZ FALKOWSKI Department of Geotechnical Engineering, Warsaw University of Life Sciences – SGGW

Abstract: Basement of the alluvia infl uence on the sing and wandering rivers (Miall 1996; channel pattern in example of selected reach of the Zieliński 1998). In the Polish Lowlands Pilica River. The type of the channel pattern is be- the most common types are meandering ing considered as indicative element of the fl uvial environment, especially for lowland, mature riv- and braided rivers. Multi-channel river ers. Investigations carried out in the Pilica River reaches defi ned as anastomosing rivers valley (example of such river) between Inowłódz (Gradziński et al. 2003) occur in Poland and Domaniewice (grant no 2P04E 069 29, Mini- in polygenic valley reaches, which often stry of Science) have shown that morphological represent adapted melt-out basins after features of the valley bottom (channel zone, as well as fl ood terrace) depends not only on river overfl ow lakes (Falkowski 1975). The regime, but also on channel zone geological set- presence of straight rivers is almost ting. Elements of the Pilica valley geology infl u- always linked with the character of the encing on fl uvial processes are protrusions of al- channel basement (Twindale 2004). Such luvia basement composed of deposits resistant to rivers occur within the outcrops of rocks erosion, crop out in the channel zone. resistant to erosion, which form linear Key words: channel pattern, alluvia basement, tectonic structures. In the Polish Low- erosion resistant deposits. land, short reaches of such rivers can be encountered near escarpments of moraine plateaus eroded by the rivers. INTRODUCTION In the history of river valleys in the The type of channel pattern is the most Polish Lowlands, climate was the main signifi cant index of the hydrological factor infl uencing the specifi c hydro- regime of a river (Allen 1970). The logical river regime and thus the type changing relations between particular of channel. Climatic changes that took elements of the hydrological regime such place in the terminal Pleistocene and the as discharge, water state, fl ow velocity, Holocene resulted in the creation of river water temperature, ice cover and sediment terraces during the evolution of present- transport (Dynowska 1971) infl uence the -day rivers. During the Last Glaciation, balance between erosional and accumula- for a relatively short time the Scandina- tion processes. Generally, fi ve main types vian ice-sheet twice (Mojski 2005) cove- of channel development are distinguished: red northern and western Poland. In the straight, meandering, braided, anastomo- ice-free area the hydrological regime of 94 T. Falkowski the rivers was infl uenced by permafrost -day terrace (Falkowski 1975, 1990; Star- (Jahn 1970) and lack of dense vegetation kel 1983). Changes in the river regime cover. At low retention of the catchment are refl ected in traces of channel migra- basin, surface runoff played a signifi cant tion that may be observed in particular role in the water balance. It supplied accumulation horizons (terraces) of river considerable amounts of sediment from valleys in the Polish Lowlands. They are the slopes to the channels. Thus, braided particularly well-recognizable on aerial rivers overloaded with sediment func- (Falkowski 1975; Szumański 1986) and tioned in the Polish Lowlands (Zieliński satellite photographs. A thorough charac- 1993; Mojski 2005). They often fi lled teristic of the infl uence of human activity the rock-cut benches of the present-day on the volume of sediment transported valleys that developed in the Eemian by rivers in the world was presented by Interglacial, forming surfaces of the Walling (2006). upper terraces. The Pleistocene/Holo- According to Wolman, Miller (1960), cene warming resulted in dense vegeta- Leopold et al. (1964), and Dury (1980), tion within the drainage basin. Increase the character of channel processes is more of surface retention caused leveling of signifi cantly infl uenced by long-term, fl ow with time and evolution of the river medium-scale phenomena and not extre- systems towards meandering rivers. The me incidents. However, during fl ood-water rivers incised into the surface of Pleis- some rivers may signifi cantly transform tocene upper terraces forming fl ood ter- the valley fl oor; as a result these trans- races (Falkowski 1975; Kozarski, Rot- formations considerably infl uence fl uvial nicki 1977; Mycielska-Dowgiałło 1978; processes that take place during long-term Wiśniewski 1987; Florek 1991; Blum medium- and low-water states. The sig- and Tornqvist 2000; Leigh et al. 2004). nifi cance of high-water states in the mor- About 6000 years BP, the hydrological phology of present-day river valleys in the regime of rivers in the Polish Lowlands Polish Lowlands is marked by the forma- began to be infl uenced by human activity, tion of the present-day terrace due to the when forest fi res and clearance were applied activity of fl ood-water. Its surface usually to gain arable ground. Such activities lies above other parts of the fl ood terrace. caused a subsequent change in the hydro- Accumulation of fi ne-grained sediments logical regime of the rivers, manifested of the fl ood facies deposited from sus- by increased surface runoff and sediment pension is much slower than aggradation supply (Falkowski 1975; Mycielska- in the near-channel zone, where coarser -Dowgiałło 1978; Starkel 1983). The material is deposited through decantation present-day rivers of the Polish Lowlands, from fl ood-water. characterized by uneven fl ow (Starkel The depth of the channel of present- 1994) typically have braided channels, -day rivers increases during fl ooding. and the process of their transformation After the fl ood wave moves downriver, under human infl uence is referred to run- the channel is fi lled with the transported ning wild (Falkowski 1975). The fl ood sediment as the transporting force of the plain adjacent to the channel formed in river decreases. In the Middle Vistula such processes is known as the present- River channel, such changes of the eleva- Basement of the alluvia infl uence on the channel pattern... 95 tion of the channel fl oor between high- constructions and fl ood embankments and medium-water may exceed 10 m (Falkowski 2007a, b). (Falkowski 2006). During fl ooding, the A trend to increase differences basement of the present-day alluvia may between extreme fl ows is presently evi- be exposed, particularly in places where dent in the hydrological regime of rivers its top lies at relatively shallow depths. in the Polish Lowlands (Ozga-Zielińska In such places the alluvial basement is 1997). The infl uence of the alluvial base- built of soils more resistant to erosion. ment on the course of channel processes, The morphology of their top surface may which during meander formation was therefore infl uence the pattern of the ri- rather low (due to balanced fl ow), is ver’s main course, and thus the processes much more signifi cant presently due to of erosion and accumulation within the increased depth of fl ood-water activity. channel and the fl ood-plain (Falkowski Features of channel morphology that are 2007a, b). Twindale (2004) pointed out indexes of a particular river regime and the relation of the river valley basement indicate the specifi c dynamics of ero- on the course of present-day channel sional and accumulation processes, are processes. increasingly dependent on the geological In regulated reaches the infl uence of setting of the channel zone, particularly the alluvial basement is often more sig- in reaches where the fl ood-water channel nifi cant than in the natural reaches. Nar- width is restricted by fl ood embankments. rowing of the fl ood-water channel by fl ood embankments increases the depth AIM AND METHODS OF STUDIES of fl ood-water erosion. In such places the infl uence of morphology of the resistant The studies carried out in the Pilica River basement on the river course concentra- valley between Inowłódz and Domanie- tion results often in damage of regulation wice (Fig. 1) were focused on determi-

FIGURE 1. Location of study area 96 T. Falkowski ning the relation of the channel zone as fl ood-terrace and the channels of the well as fl oodplain morphology (contem- studied rivers were also analyzed. Soil porary and Holocene channels pattern) analysis as well as sedimentological and with the morphology and lithology of the pollen analysis of the alluvial sediments alluvial basement. The channel pattern is were conducted. The studies were made connected with a specifi c variability of in the frame of project no 2P04E 069 29 alluvial soil properties (Myślińska 1984; Signifi cance of morphogenetic factors in Kraużlis et al. 2003). Morphogenetic the development of habitat variability in units corresponding to particular stages selected reaches of river valleys in the of the fl uvial setting evolution (refl ected Polish Lowlands, fi nanced by the Mini- in the channel pattern) are often the basis stry of Science and Higher Education of of units applied in documenting the geo- Poland. logical-engineering conditions of river valleys (Falkowski 1990; Gilvear 1999). RESULTS The studied reach of the Pilica River valley incises into a fragment of a plateau The analyzed fragment of the Pilica with a mature, denudation morphology, valley is developed in Middle Jurassic developed since the end of the Middle siliceous sandstones and in various Pleis- Polish Glaciations. The rock-cut bench tocene deposits (Figs 2, 3). Locally the of the valley was formed partly in Middle sandstones crop out in an embankment Jurassic rocks and partly in glaciogenic of a plateau adjacent to the valley (Kłoda deposits (Kłoda 1993). 1993). Above them occur medium and The study included geomorphologi- coarse sands with gravel, considered cal analysis of the terrace surface based as Pleistocene alluvia from the Eemian on aerial photographs. Surfaces of the Interglacial and the Vistulian Glaciation. valley fl oors, as well as geological dril- They compose also the upper terraces in lings that document the surface of the the valley (Kłoda 1993).

FIGURE 2. Schematic longitudinal geological cross-section through the Pilica River channel zone between Inowłódz and Grotowice; J – Jurassic sandstones, mp – moraine deposits (Pleistocene), ap – allu- vial sands and gravels (Pleistocene), ac – channel facies alluvia of contemporary river, L – residual lag Basement of the alluvia infl uence on the channel pattern... 97 2 4 Domaniewice oss-sections A-A, 2 2 3 C C 4 1 km 2 Grotowice B B 2 ood water reworked terrace, 4 – upper terraces and upland 2 fl 4 1 2 A A Pasternik 3 1 4 4 owice ã d 1 įĈ 2 ódz ã Inow B-B and C-C; 1 – contemporary terrace, 2 meandering river 3 FIGURE 3. Geomorphological sketch-map of the studied valley fragment displayed in relation to orthophotomap with location cr 98 T. Falkowski

Above the Pleistocene deposits, on over 1.5 m at medium-water. Numerous a bed of gravel-pebble lag occur depo- longitudinal islands and shoals dividing sits representing the fl ood terrace of the the main course into branches are present Holocene Pilica River (Figs 4, 5, 6). in the channel. The braided character is They are composed of a part formed by confi rmed by sedimentological analysis a meandering river and a part formed of the present-day alluvia (Falkowski, presently by a braided (wild) river. Górka 2009). The present-day terrace (fl ood-water In the studied reach of the Pilica chan- channel) bears morphological features of nel fl oor crop out deposits of the alluvial a braided river setting (Fig. 3). The chan- basement that are resistant to erosion (Fig. nel is shallow, rarely exceeding depths 2). They include Jurassic sandstones, as

FIGURE 4. Transverse geological cross-section A-A through the fl ood terrace of the Pilica River (loca- tion on Fig. 3: explanations on Fig. 4); J(S) – Jurassic sandstones, dr – decomposed rock, mp – moraine deposits (Pleistocene), ap2, ap1 – alluvial sands and gravels (Pleistocene), am – channel facies alluvia of meandering river (Holocene), ar – reworked alluvia (Holocene), ac – channel facies alluvia of contempo- rary river, ac(f) – fl ood deposits of contemporary river, o – organic deposits, af – alluvial fan, L – residual lag Basement of the alluvia infl uence on the channel pattern... 99

FIGURE 5. Transverse geological cross-section B-B through the fl ood terrace of the Pilica River (loca- tion on Fig. 3; explanations on Fig. 4) well as moraine and ice-dammed depo- These traces are not, however, evidence of sits. Residual lags are common, composed lateral migration of the channel as in the of pebbles and cobbles. They typically lie case of other rivers in the Polish Low- on exposed glacial till. Deposits resistant lands (Vistula River valley − Falkowski to erosion form stabilizing protrusions in 1975; Prosna River valley − Kozar- the river profi le. Some of them are co- ski, Rotnicki 1977; San River valley − vered by thin channel alluvia. Between Szumański 1986). The only evidence of the protrusions the thickness of channel meandering of the Pilica River is arch- alluvia may reach 7−8 m. -like ox-bow lakes on the terrace sur- The remaining part of the fl ood terrace face. The thickness of the channel facies adjoining the present-day terrace bears building this form reaches c. 5−6 m (Figs traces of meandering processes only in 4, 5, 6). Deposits include medium sands the Pasternik and Grotowice area (Fig. 3). and medium sands with gravel. The top 100 T. Falkowski

FIGURE 6. Transverse geological cross-section C-C through the fl ood terrace of the Pilica River (loca- tion on Fig. 3; explanations on Fig. 4) part of the meandering river succession ternik (Fig. 3) the terrace surface contains composed of fl ood facies differs from the numerous longitudinal mid-channel sand fl ood facies of other rivers in the Polish bars separated by high-sinuosity chute Lowlands (Myślińska 1984). They lack channels. Differences in elevation on the cohesive deposits and are dominated by surface reach occasionally 2 m. The sur- silty and fi ne sands with humus. Very face is covered by c. 3 m thick succession rare are thin intercalations of clay and comprising medium sands with gravel silt and organic muds. As show by pollen and locally fi ne and silty sands. Residual analysis, organic deposits from this part lag composed of gravels and pebbles of the succession were redeposited in occurs in its base (Figs 4, 5). modern times. Downriver from Grotowice, the sur- The remaining part of the studied sur- face of the valley fl oor was also trans- face bears traces of transformation by formed by fl ood-water (Fig. 3). Traces of fl ood-water. Between Żądłowice and Pas- meandering are not preserved here. On Basement of the alluvia infl uence on the channel pattern... 101 aerial photographs are visible traces of is thus partly the effect of restricted ero- chute channels with similar sinuosity as sion in this part of the valley. During the between Żądłowice and Pasternik. The Holocene climatic optimum, when Pilica surface is, however, fl at and devoid of was a meandering river, the alluvial distinct accumulation forms. Similarly as basement did not considerably infl uence in the Żądłowice area, the basement is the fl ood-water fl ow, which is the result composed of fi ne and silty sands; residual of hydrological regime, particularly fl ow lag was not noted in their base (Figs 5, 6). balance. The most signifi cant infl uence of the morphology of the fl ood terrace has ice- DISCUSSION -jam water. Zones of the basement pro- The studies show that the present-day trusions were probably places where morphogenesis of the Pilica River in the ice-jams generated. The link between the analyzed reach depended on the alluvial occurrences of deposits resistant to ero- basement. Protrusions occurring in the sion in the basement with the frequency valley channel, composed of deposits of ice-jams was determined in the Middle resistant to erosion, such as sandstones, Vistula valley (Falkowski, Popek 2000). and moraine and ice-dammed deposits Overfl owing waters generated due to covered by residual lag stabilize the ice-jams upriver from Żądłowice pro- longitudinal profi le of the channel and bably destroyed a fragment of the upper deep erosion. Studies of the channel terrace, transforming at the same time the zone showed the presence of exposures surface of the terrace formed by mean- with organic soils, mainly peats, in dering the Pilica River. This is evidenced reaches containing protrusions of the al- by a residual bed located at the depth of luvial basement. Pollen analysis of these 2−3 m. Sediment transported by fl ood- deposits indicates their Holocene age. -water formed the morphology of the The stabilizing role of the rock benches area between Żądłowice and Pasternik, protects these deposits against erosion. removing or burying traces of meande- Evorsion does not take place in these ring. Downriver of Grotowice, the fl ood- localities. -water did not carry such quantities of Floods that occur in the Pilica River sediment. The top part of the alluvial valley in the studied reach are rather rare succession of the meandering river was and of low magnitude due to the presence transformed, but a residual layer was not of an artifi cial Sulejów water reservoir formed. Only the uppermost parts of the located c. 30 km upriver. However, even Holocene succession (fi ne-grained fl ood before the reservoir was built, erosional facies) were subject to reworking. Buried deepening of the channel did not take traces of meanders fi lled with organic place in the bench zones. The overfl owing soils were determined only in the down- water was transported over the terrace river part of the analyzed reach. surface, and traces of this process are the Despite the lack of regulation struc- network of erosional fl ood-water chan- tures (in the analyzed reach the Pilica nels on the surface of the present-day ter- River is not regulated), strangely enough race. The braided pattern of the channel the present-day river has chosen a zone 102 T. Falkowski to the right of the valley axis for its fl ow. a review and look forward, Supl. Sediment. 47, Here occur protrusions of the alluvial 2–48. basement composed of deposits resistant DURY G.H., 1980: Peak Flows, Low Flows, and Aspects of Geomorphic Dominance, w: K.J. to erosion. Cross-sections indicate that Gregory (red.) River Channel Changes, John to the left of the valley axis the top of the Wiley & Sons, 61–74. alluvial basement lies at lower depths. DYNOWSKA I., 1971: Types of river regimes In Poland; Zeszyty Naukowe U.J. CCLXVIII, Prace Geografi czne, z. 28, ss. 150 (In Polish). CONCLUSIONS FALKOWSKI E., 1975: Variability of channel processes of lowland rivers in Poland and A crucial factor infl uencing the course changes of Valley fl oors Turing Holocene; Biu- of present-day channel processes in the letyn Geologiczny Uniwersytetu Warszawskie- analyzed reach of the Pilica River, inclu- go 19, 45–78. ding its braided character, is the alluvial FALKOWSKI E., 1990: Morphogenetic classifi - cation of river valleys developing in formerly basement. glaciated areas for needs of mathematical and Infl uence of the basement may reach far physical modeling in hydro technical projects. beyond the channel zone, thus the analy- Geographia Polonica vol. 58, 55–67. sis of channel pattern changes observed FALKOWSKI T., 2006: Factors of natural stabi- on the entire surface of the fl ood terrace lity of the Middle Vistula River channel zonej; (e.g. in the pattern of photolineaments on Wydawnictwo SGGW; Rozprawy Naukowe i Monografi e, ss. 128 (In Polish). aerial or satellite photographs) may indi- FALKOWSKI T., 2007a: Geomorphological anal- cate the channel state and be the base of ysis of a The Vistula River valley in evalua- predictions on the evolution of channel ting the safety of regulation structures; Acta processes. Geologica Polonica Vol 57 (3) 377–390. The author’s experience with selec- FALKOWSKI T., 2007b: Alluvial bottom geolo- gy inferred as a factor controlling channel fl ow ted reaches of other rivers in the Polish along the Middle Vistula River, Poland; Geo- Lowlands (e.g. the Bug, the Narew, the logical Quarterly 51 (1), 91–102. lower Oder, the middle and lower Vis- FALKOWSKI T., GÓRKA M., 2009: Sedimenta- tula rivers) evidence that infl uence of the ry structures and their usefulness in the Polish basement is favoured by the lack of bal- Lowland river valleys management; Nauka anced fl ow in the river and the resulting Przyroda Technika, Wydawnictwo Uniwer- sytetu Przyrodniczego w Poznaniu; Melioracje increase of fl ood-water erosion (rewor- i Inżynieria Środowiska, tom 3, zeszyt 3, # 81 king of alluvial sediments). The observed (In Polish). trend of increasing difference between FALKOWSKI T., POPEK Z., 2000: Zones of ice- the extreme states of the lowland rivers -jams formation on the Middle Vistula River should attract signifi cant attention to reach in relation to variable of river valley mor- phology; Annals of WAU, Land Reclamation such forms. No 30, 77–90. FLOREK W., 1991: Postglacial development of REFERENCES River Valley in the Middle part of the northern slope of Pomerania, Wyższa Szkoła Pedagogi- ALLEN J.R.L., 1970: Physical processes of czna, Słupsk, 142 pp. (In Polish). sedimentation; George Allen and Unwin LTD, GILVEAR D.J., 1999: Fluvial geomorphology London. and river engineering: future roles utilizing BLUM M.D., TORNQUIST T.E., 2000: Flu- a fl uvial hydrosystems framework; Gemorpho- vial response to climate and sea-level change, logy 31, Elsevier, 229–245. Basement of the alluvia infl uence on the channel pattern... 103

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