GEOGRAPHIA POLONICA 2010, 83, 1, 25–37

HYDROTECHNIC STRUCTURES ON THE POMERANIAN RIVERS – A REACTION TO EXTREME HYDROLOGIC PHENOMENA IN THE 19TH CENTURY (IN THE EXAMPLE OF THE UPPER )

WACŁAW FLOREK, JOLANTA JAROMIJ, MAGDALENA SKWIERAWSKA Department of Geomorphology and Quaternary Geology, Institute of Geography and Regional Studies, Pomeranian University in Słupsk, Partyzantów 27, 76-200 Słupsk, Email: fl [email protected]; [email protected]; [email protected]

Abstract: In the 19th century throughout Central Europe fl oods became increasingly intense; a similar situation pertained in the area of lake districts and the coastal zone. Maximum water levels recorded at the end of the 19th century (particularly in the years 1888-1892) to the present day on many water- gauge stations (particularly those located in rivers’ lower courses) were the highest ever observed. Yet in the half on 19th century the need for regulation works became increasingly apparent. On the Pomeranian rivers these works began in 1860; they reached their greatest intensity in the fi rst twenty years of 20th century. Regulation activity was conducted which led to a distinct shortening of riverbeds; on longer sec- tions of the river the reduction amounted from over 12 to 20 or more percent, in some places even 50%. It caused the aggravation of bottom erosion, and also lateral erosion, which was particularly apparent beneath the water power stations. In the last few decades the ending of work that interferes with the riverbed has resulted in the gradual restoration of the primary character of Wieprza River bed. It is also worth mentioning that even when notable fl oods have appeared (for example, in 1980), which were comparable to those that appeared at the end of 19th century, they did not lead to any fundamental change to any section of the Wieprza River bed geosystem.

Key words: hydrotechnic structures, Wieprza river, fl ood, river bed response, reservoir, fl oodplain.

INTRODUCTION of the century (especially during the years 1888-1892), and at many stations, particu- In the middle of the 18th century large larly those located on the lower parts of the land improvement projects were initiated in rivers, they remain the highest ever record- the lake district of . At that time, ed (Fig. 1). As early as the middle of the 19th and also later, these were mostly drainage century the fl oods generated pressure for systems, which must have resulted in in- river regulation works. On the Pomeranian creased irregularities of fl ows (probably the rivers the works began in 1860, but most of 18th century engineers were not aware of the construction was carried out during the this). In the 19th century, fl ooding increased fi rst two decades of the 20th century. in the whole of Central Europe, and also in River training works included the deep- the lake district and coastal areas. Maxi- ening of river beds, the removal of boulders, mum water levels were recorded at the end trees, sandbars from the channels, but most

http://rcin.org.pl 26 Wacław Florek, Jolanta Jaromij, Magdalena Skwierawska

SMO£DZINO STARY KRAKÓW 272 461 1-3.04.1888 31.01.1892 S£UPSK 334 31.03.1888

BIA£OGARD TYCHÓWKO 384 480 29.03.1888 30,31.01.1892

PI£A 464 31.03.1888 DRAWINY Other periods with 241 absolutly maxima 20.03.1888; 1931-1932; 1940; 1947-1953; 12.19.1923 1967-1970; 1979-1982

Figure 1. Division of Pomerania into watersheds and the location of water level gauges with maxima for the period 1888-1892. of all the removal of river bends (mean- many rivers into autonomous stretches (Ra- ders), the strengthening of river banks and chocki 1974). the building of weirs, dams and reservoirs. The fi rst phase of the investigations pre- At the turn of the 20th century, relatively sented below was fi nanced from the funds large hydroenergy projects were initiated. of the Pomeranian Pedagogical Academy in One consequence of these regulation ac- Słupsk; later phases were fi nanced from the tivities was that river beds were signifi cant- grant PBZ-KBN-086/P04/2003 “Extreme ly shortened; over longer stretches the re- meteorological and hydrological events in duction could be between a dozen and over Poland (assessment of events and evalu- twenty percent (Florek, Nadaczna 1986); ation of their impact on human environ- locally it could be as much as 50% (Florek ment)”; the grant leader was prof. dr hab. 1991). This resulted in the strengthening of Jacek Jania at the Department of Earth Sci- bottom and bank erosion, especially below ences, the Silesian University), Task 5.5.4. the power plants, due to the increased fl ow “Regularities of extreme event progress in velocities generated by the increased slope valley bottom areas” and Task 5.5.8 “Infl u- of the river bed and by the insuffi cient dissi- ence of extreme events on the functioning pation of energy of the relatively sediment- of geosystems of the coastal zone free water below the power plant. and of river valleys of near-coast areas”. The completion of some of the projects, such as on the middle Słupia River, caused a radical restructuring of the drainage sys- HYDROLOGICAL PROPERTIES OF THE tem, and changed the rhythm and range of UPPER WIEPRZA CATCHMENT AREA the water fl ow below the hydropower plants (W. Florek 1991, E. Florek 2001). With re- The slope of the Wieprza decreases gard to erosion, sediment transport and ac- gradually though rather irregularly along cumulation, especially of the coarser grains, the river course. Where the river cuts the dams and weirs divided the channels of through the glacial outwash of the Pomera-

http://rcin.org.pl Hydrotechnic structures on the Pomeranian rivers... 27 nian ice-marginal valley (below Bożanka), Physiographical (the diverse relief of the the decrease of the river slope is especial- terrain, with numerous undrained hollows, ly visible. Above it, on some stretches the and a high percentage of forest cover) and Wieprza the decline even exceeds 5‰. The climatic conditions facilitate a signifi cant average fl ow velocity on the upper Wieprza equalization of fl ow-off from the upper part is 0.5 m/s. of the Wieprza catchment area. This is re- According to Dębski (1978), the hydro- fl ected by the relatively small differences of logical regime of the rivers of the north- water levels both in the Wieprza river chan- ern slope of Pomerania, including that of nel (profi le Kwisno at km 102.4 – 0.6 m, Wieprza, is a typical example of an oceanic profi le Broczyno at km 84.1 – 1.2 m) and in snow-rain system, and Dynowska (1971) the Studnica river channel (profi le Ciecho- defi ned it as a soil-snow rain system with lub at km 2.2 – 1.12 m) (Table 1). The maxi- a balanced distribution of fl ows. It is a two- mum discharge occurs in the upper Wieprza seasonal regime, with a shallow summer during the fi rst months of the year, mainly in low and a rather low winter/spring fl ood. January and March. At the profi le at Kwisno Low water levels occur on the Wieprza a minimum discharge was recorded during during the summer, most often in July. The nearly all months of the year except the fi rst high waters are not very high; they are re- three, while at the station Broczyna they corded in March, January or December, and occurred most often in June, July and Sep- they are of the same order of magnitude tember. It is worth noting that the difference (Mikulski 1963). between dry and wet years mainly relates to

m a.s.l. 129 Wieprza river Kwisno gauge station km - 102.4, A - 96.4 km2 128

127

126 WWW=217 cm 17.05.1970 125 SW=168 cm 1974-1983 NNW=147 cm 124 07,12, 20.06.1979

123 0 1020304050m

m Wieprza river Korzybie gauge station a.s.l. 2 36 km - 60.6, A -860 km 34 WWW=210 cm 32 14.03.1940 SSW=85 cm 30 NNW=5 cm 27.04.1990 28 26 24 22 0 50 100 150 200 m

Figure 2. Transverse profi les of the upper Wieprza river bed at Kwisno and Korzybie; the reach of extreme water levels and the average water level in the decade 1974-1983.

http://rcin.org.pl 28 Wacław Florek, Jolanta Jaromij, Magdalena Skwierawska min :Q max Q min :Q mean :Q max 3.68:1.0:0.47 7.8 2.76:1.0:0.30 8.9 Q 4.29 0.86 3.11:1.0:0.38 8.87 3.89 3.26:1.0:0.58 5.49 8.95 Mean for 1951-1975 (1961-1975) (1961-1975) 2.02 0.31 2.25 2.76 Absolute minimum 3 IX 1975 18 VII 1982 4-14 IX 1976 10,11 X 1969 10,11 10 VII, 15 VIII, 15.8 2.68 24.7 12.7 5 I 1982 Absolute 1 IV 1979 1 IV maximum 19 IV 1970 19 IV 18 IV 1970 18 IV 51 68 170 120 Mean for 1956-1975 (1961-1975) (1966-1975) (1966-1975) (1974-1983) 32 10 88 157 Absolute minimum ow in the Wieprza and Studnica rivers (Rocznik Hydrologiczny Wód Powierzchniowych...). and Studnica rivers (Rocznik Hydrologiczny Wieprza ow in the 27 VI 1966 fl Water level (cm)Water Flow ( m³/s) 16,17 V 16,17 V 1959 10,11 X 1969 10,11 2-4, 7 VI 1978 2-4, 7 200 Absolute 18 I 1982 maximum 7,8 II 1963 14 III 1940 17 IV 1970 17 IV area [km²] Catchment Station km Kwisno 102.4 96.4 217 Broczyna 84.1Korzybie 381 60.6 860 150 210 Ciecholub (Studnica) Table 1. Average and extreme water levels Average 1. Table

http://rcin.org.pl Hydrotechnic structures on the Pomeranian rivers... 29 late autumn and winter (November-March), generally in early spring. The implementa- with wet years having discharges decidedly tion of these projects also coincided with higher than average. the beginnings of hydropower expansion. A comparison of data on the variability of water level and discharge on the upper Wieprza with the cross-section at Kwisno ECONOMICAL INGERENCE INTO (Fig. 2) shows that even during the highest RIVER BEDS AND VALLEY BOTTOMS water levels the water is contained in the AND ITS IMPACT river bed, and does not fl ow out onto the fl oodplain. The situation is different at Ko- The main rivers of the upper Wieprza rzybie, where extreme water levels caused catchment (Wieprza and Studnica) have the inundation of the whole fl oodplain. been used for various purposes for quite a These data indicate that the occurrence long time. There is historical evidence that of extreme 19th century fl ows and, connect- from at least 1562 they were used for fl oat- ed with them, extensive inundations cover- ing timber, though this type of transport th ing the whole fl oodplain, would at that time became popular in the 19 century (Fig. 3; have caused concern for farmers engaged in Lindmajer 1997, 1999), and disappeared in extensive stock farming, and stimulated the the 1930s, after a dense network of surfaced th initiation of land reclamation and river train- roads was built. Especially in the 18 and th ing projects, which aimed mainly to provide 19 centuries, many plants powered by hy- the rapid drainage of water from the river droenergy were built in junker estates, such valley bottom during high water levels, i.e. as fulling mills, sawmills, and water mills.

Wieprza

Baltic Sea Dar³owo S£AWNO

Gwiazdowo ¯ukowo Barwino £êtowo Osieki Warcino Bronowo Oblê¿e Osowo ¯elice Popielewo- Biesowice Popielewko Ciecholub Trzebielino Wêgorzyno Broczyna Kunica Polanów P³acko Bo¿anka Œwierzno- Trzcinno Wieprza Œwierzenko Studnica Kawcze Kwisno

MIASTKO

SMALL MODERATE BIG INTENSITY INTENSITY INTENSITY PARTS OF RIVERS USED FOR TIMBER RAFTING

Figure 3. The geography of timber rafting on the Wieprza and Studnica in the third quarter of the 19th century (according to J. Lindmajer 1997).

http://rcin.org.pl 30 Wacław Florek, Jolanta Jaromij, Magdalena Skwierawska

These were generally located on valley in 1913 and Kępice (km 73.6) in 1918. The stretches of glacial trough origin (because construction of these power plants was con- of the larger river slope). From the begin- nected with the partitioning of the river ning of the second half of the 18th century, channel and valley bottom by earth dams investment into land improvement steadily and weirs, and the creation of reservoirs. At increased. From 1843 they were undertaken least since the fi rst half of the 19th century by water partnerships; these were replaced (before 1849) there was a weir with a water at the turn of the 20th century by land im- mill at km 2.2 of Studnica valley. The water provement offi ces. These offi ces developed mill was later replaced by a power genera- systems (hillside and ridge) that irrigated tor. The partitioning of Wieprza disturbed the higher parts of the valleys and drained the fl ow of the coarser sediments, and con- the lower parts. River training works be- sequently the effective part of the Bieso- gan in 1860, i.e. after the fl oods; their im- wice reservoir became completely sanded pact and reach have not been documented up. This was also strongly facilitated by the by systematic observations. The land im- removal of many hydrotechnic installations provement and river training works in the on the upper Wieprza and Studnica, as a re- Wieprza valley were carried out mainly sult of the pre-emption policy of the central along its glacial outwash stretch (below government in the 1950s and 1960s, which Bożanka). The hydroelectric power plant strengthened river channel processes. In ef- at Biesowice (km 80.88 of Wieprza) started fect, many erosion niches appeared, the river operation in 1908 and is still working to- channel separated into branches because of day (Fig. 4). The next hydroelectric power numerous clumps, and a tendency emerged plants began to operate at Kępka (km 78.26) towards curving the formerly straightened

WIEPRZA (km 77.50 - 82.00)

HYDROPOWER STATION KÊPKA

HYDROPOWER STATION BIESOWICE

1

2

3

Figure 4. State of the Wieprza channel near the Biesowice and Kępka hydro- power plants; 1- bank grown over with turf plants, 2 – bank grown over with bush abd trees, 3 – bank artifi cially strengthened.

http://rcin.org.pl Hydrotechnic structures on the Pomeranian rivers... 31 stretches of the rivers. Generally, the Stud- river channel width varies between 10-12 nica channel is much more stabile than the m, the average depth is 1.0-1.2 m. Along upper Wieprza channel (Fig. 5). the river, alternatively on both sides, there are narrow wet meadows, grown over with THE PRESENT STATE OF THE sedge and alder trees. The ditches draining UPPER WIEPRZA BED NEAR THE the fl oodplain were not cleaned for a long HYDROELECTRIC POWER PLANTS time and have now disappeared completely. AT BIESOWICE AND KĘPKA On the edge of the meadows, at the foot of the slope bordering the bottom of the val- The Wieprza fl ows above the Studnica ley, there are quite numerous oxbow lakes, outlet (km 80.4) in a valley whose width and also springs and seepages. Approaching ranges from 100-150 m to a maximum 250 the Studnica outlet, the Wieprza channel re- m. The slopes of the valley are wooded and mains fairly compact, in spite of the many reach 20-40 m above the bottom of the val- traces of erosion and local damming by ley. The average slope of the river is along fallen trees. At places where the river mean- this stretch is about 1‰. In the upper part ders have narrow necks, e.g. below km 88, of this stretch, the river continually mean- the river is close to shortening its course. ders, easily eroding its sandy banks in the This has happened above km 87, though bends. According to information contained fl ow through the meander has not yet been in the Ekspertyza... (1957), in the past local stopped completely (the neck is 2 m wide). people protected the eroded banks by sink- Beginning from km 87, the river does ing along them felled trees. Furthermore, not curve so much as in the section above today many fallen trees lie in the river. The it, but its tendency to erode the banks is still

STUDNICA (km 28.95 - 35.00)

46

47

MIASTKO

PASIEKA

1

2

3

Figure 5. State of the Studnica channel near Miastko; explanation as in Fig. 4.

http://rcin.org.pl 32 Wacław Florek, Jolanta Jaromij, Magdalena Skwierawska present. In the past, the Wieprza meandered the meadows are used for agriculture. There at this point intensely, as is shown by two are some small copses. Below the bridge at rather large oxbow lakes on the right bank Biesowiczki the valley becomes narrower, (at km 86 and above km 85). On a Prussian the height of the valley slopes, which are map that dates from the end of the 19th cen- covered by leafy trees, is about a dozen me- tury they are shown as connected with the tres. The hydropower plant reservoir, below river channel. Low lying parts of the mead- the timber bridge, previously took up nearly ows are boggy, because the drainage ditches the whole width of the valley bottom. After have not been maintained. Above the con- reconstruction in 2002, a part of the fl ood- nection with Studnica there is an island plain was left outside the dykes bordering which divides the river channel into two the reservoir (Fig. 4). Because of the intense branches. On the bottom of the bed grow accumulation of sediments the reservoir re- watercress (Nasturtium offi cinale R.Br.) and quired systematic dredging. At present, the white water-buttercup (Ranunculus aqua- dredged spoil is used for the building up of tilis L.); and closer to Studnica also grow dykes and for increasing the height of parts spiny waterstarwort (Callitriche verna L. of the foodplain outside the dykes. em. Loennr.) (a plant typical for Studnica). Late 19th century Prussian topographic On this stretch the Wieprza changes its maps show that above the bridge at Bieso- direction from west to north-west, and with wice there was a water mill on the right bank that change, near the Darnowskie Lake, it of the river. It was probably built between leaves the distal valley and fl ows into the 1780 and 1789 (Florek, Nadaczna 1986), bottom of a sub-glacial trough (Sylwestrzak a conclusion drawn from a comparison of 1977). maps made by Gilly (published in 1789) From the connection with Studnica and Schmettau (from the years 1770-80). onwards, the Wieprza increases its cross- The damming structures of the Bieso- section attaining, on the stretch to the hy- wice hydropower plant are located at km dropower plant at Biesowice (except on a 80.88 (Fig. 4). The power plant was built part of the old reservoir), a channel width in the period 1906-1908. The upper water 12-15 m and mean depth of 1.2 m (which level comes to 52.0 m, and the lower water is dependent on its distance from damming level is 47.4 m a.s.l. The river fl ows from structures). The slope of the river is very the power plant in three branches – the left gradual. Meadows on both sides are slightly and right pass through the turbines (Fig. 4), inundated by dammed up water. Bulrush the central branch goes through a weir, (Typha latifolia and T. angustifolia) and which is opened when needed. Directly be- reed grow in the river channel. The banks low the branches connect into one channel. are low, and willows grow on them (Fig.4). The banks are artifi cially strengthened: the Above km 83 the river fl ows under a rein- right with a concrete structure, further down forced concrete arch bridge on the Bieso- with fascine, the left with stones. Several wiczki-Przyjezierze road. The backwater of dozen metres below the power plant, there the Biesowice reservoir reaches about 350 are small holms fi xed by alder trees, and m below the bridge (Operat wodno-prawny an island formed by a division of the river, elektrowni wodnej w Biesowicach [Water- which previously fl owed only through the legal documentation for the hydroelectric right branch. The island is about 70 m long power plant at Biesowice]), i.e. to the place and 30 m wide, with beech trees growing where the water surface is at the ordinate on it. 52.40 m above s.l. The valley slopes above

http://rcin.org.pl Hydrotechnic structures on the Pomeranian rivers... 33

Until the backwater of the Kępka hydro- 77.96. From here the river fl ows in a curv- electric power plant’s reservoir the generally ing channel 12-15 m in width and 1.5 m in steep river banks are naturally strengthened depth, with a till bottom. There are many by the trees that grow there (mainly beech, fallen trees in the river. Very occasionally although further away there are some pine small meadows also occur. The level of trees), except the 3 m high stretch of river bank erosion is small. bank by the aforementioned island, where traces of sliding due to side erosion are vis- ible. Along the whole stretch the river bed THE STATE OF THE STUDNICA is often dammed by fallen trees. The river CHANNEL NEAR MIASTKO slope is signifi cant, the river channel width is 10-16 m, and has a depth 0.5-1.2 m, and The beginning of the Studnica is in a the bottom is stony. Higher terraces of the chain of lakes, the fi rst of which is Lake valley are covered mainly by pine forests. Słosineckie Małe; there then follow the Water velocity becomes much smaller lakes Sitno Duże, Sitno Małe and Studzien- at km 80 because of the backwater of the iczno. The outfl ow from the last lake is con- Kępka reservoir. This is a 2 km long stretch sidered to be the proper starting point of the of the river. The reduction in velocity is also Studnica. About 50 m from the lake there is related to the increased water depth. How- a concrete weir that was constructed in 1974 ever, in places where parts of the fl oodplain to manage water levels and to guarantee the have become inundated, the water is shal- water supply to the fi sh farm at Pasieka near low, and willows and shallow water plants Miastko. A similar weir was built at the grow abundantly. The average depth of the same time near Świerzenko. Both weirs lift reservoir is 1.36 m, and the maximum depth the water level by 1.5 m. The water level close to the dam is 3.6 m. The ordinate of in the lake is permanently lifted by 0.7 m, the water surface at the dam is 46.6 m a.s.l. which ensures a stable fl ow of 350-450 l/s Generally the banks are high (being the edg- (previously it was 120-600 l/s). Additional- es of higher terrace levels) and are covered ly, on a stretch that measures 750 m the river by pines. At km 79 a left tributary fl ows into channel was deepened, and now the depth is a reservoir – the Modła. Towards the hydro- 0.6-0.8 m, the width is 3-4 m and the river power plant, the left bank becomes lower, slope is small (below 2‰). In the past the and the width of the reservoir narrows from river channel was regulated, which is indi- 100-200 m to about 50 m. The Kępka hy- cated by the remains of piles at the banks; to- dropower plant is located at km 78.26. It day, though, the river is irregular. The chan- was built in 1913 to supply power to the nel is covered by the reed Phragmites com- paper-mill at Kępice. It operated until 1945, munis) and the bulrush (Typha latifolia and and again began to operate in 1998. Above T. angustifolia), but there is no underwater the power plant the left bank is strengthened vegetation. There can often be found in the by a concrete structure and the right bank is river fallen trees, and blockages caused by naturally protected by bushes. vegetation and large rocks. This locally lifts Below the power plant at Kępka (the the water level even up to the edge of the lower water surface comes to 41.39 m bank, which also serves to increase the wet- a.s.l.), the river bed has been artifi cially ness of the valley bottom, which in addition strengthened: the bottom and the right bank to this has many springs and other ground are supported with concrete, the left bank water outfl ows. Most of the valley bottom with stones. There is a timber bridge at km is covered by wet meadows with sedge and

http://rcin.org.pl 34 Wacław Florek, Jolanta Jaromij, Magdalena Skwierawska moss; the direct neighbourhood of the river (Fig. 5). The last river training and land is covered by alders and osiers. The remains improvement works were carried out in the of a damming timber structure which was years 1990-95. This is the only stretch with once a water mill are located at the end of these attributes along the whole river length. this 750 m long stretch, and on the bank are The average width of the river channel is the stone foundations of the mill. 3.5 m, and the water depth is 0.3-0.45 m. The From the point of the remains of the mill bottom is sandy or stony. Directly below the (km 35.94) the slope of the river increases fi sh ponds the Studnica receives a left tribu- to over 5‰, and along a 1 km long stretch tary, the Pląsy stream, which is regulated on the river fl ows in a curving channel through its lower part. A further tributary, this time a narrow valley with steep slopes. The Stud- on the right, joins the river 200 m below the nica at this point is 4-5 m wide, its depth is ponds. It is an unnamed stream, regulated only 0.1-0.2 m, and the river bed is gravelly along the whole of its length. The river be- with many stones, and is often jammed by low the timber bridge was in the past within fallen trees. The banks are densely grown reach of the backwater of the water mill in over with alders. On the left, steep slope of Miastko, and because of that it was protect- the valley are boggy meadows with sedge, ed on both sides by low dykes, which are moss, horsetail, and sometimes reed. Nu- still in place and have remained unchanged. merous springs occur over the whole area At the back of the dykes there are, parallel of the meadows. to the river, the main ditches of the system Along the fi sh farm at Pasieka the river that drains the meadows through which the slope declines to 3-3.5‰. The width of the river fl ows. These ditches are connected channel also becomes smaller, locally to as above the town with the river channel by a little as 2 m, and the depth increases (up to water trap, through which water is led to the 0.5 m). In the past the river was regulated lower level water at the water mill in Mi- along this stretch, but has now returned al- astko. In the town, the Studnica passes un- most completely to its former, natural state. der several bridges. The fi rst is a reinforced Meadows lie along the banks covered by al- concrete road bridge on the Mistko-Bytów ders and osiers. There are numerous springs road. This is the fi rst time water vegeta- (at the foot of slopes and near the river chan- tion appears in the river: duckweed (Lemna nel). The ditches draining water from them minor L.), hornwort (Ceratophyllum demer- have been destroyed and no longer serve sum L.) and white water-buttercup (Ranun- their original purpose. To a large extent the culus aquatilis L.. Probably this is connected area is being taken over by alder bushes; with the higher fertility of the water caused gradually the meadows and pasture land are by the discharge of waste water from the being replaced by alder forest habitats. town area. The second reinforced concrete Above Miastko, at Pasieka, there are bridge is on the Miastko-Słupsk road, and fi sh ponds on the Studnica, which use the 10 m further down is the inoperative water whole water fl ow of the river. Water intake mill. At present it functions as a weir, lifting is ensured by a concrete weir which lifts the the water surface by 1.8 m. 40 m below the water surface by 2 m. The fi sh are raised weir the river fl ows under a concrete bridge in two tanks, which also serve as settling on the previous road to Słupsk, and about tanks. From this point, until the inoperative a dozen metres further ends the regulated water mill in Miastko, the river is regulated urban stretch of the Studnica (Fig. 5). for 1800 m, and the land along it has a land Until the destroyed railway bridge, on improvement system that is in operation the dismantled Miastko-Bytów railway line,

http://rcin.org.pl Hydrotechnic structures on the Pomeranian rivers... 35 the Studnica fl ows through a once regulat- named left tributary fl ows into the Studnica, ed, and now no longer maintained, channel and below is an object defi ned as the “stone of 3.5-7 m width and 0.1-0.5 depth, with a rapid Gatka-Łodzierz”. In the past there was varying declining gradient (0.5-3‰). Still a textile factory in this location, but no trace within the town limits, there is a short, fast of it remains today. Below the rapids, the stretch in a shallow ravine, below which the water is dammed up by a mound of rubble fall gradually becomes smaller and the av- which came from a railway bridge that was erage depth increases. The river channel is blown up during the war (km 30.52). The more compact at this point, the bottom is river fl oods over onto the banks, which are sandy and muddy, and is covered by vegeta- covered by alders, reed and bulrush (Typha tion. In several places traces of bottom and latifolia and T. angustifolia). The river chan- bank erosion are visible. In some places on nel on this stretch is overgrown; the steeply the bank there are reed (Phragmites com- sloping right-bank meadows are boggy due munis) and bulrush (Typha latifolia and to numerous springs and are overgrown T. angustifolia). On the left bank, between with sedge and moss. On the dry left bank the town area and the river are rather wet there are pastures. meadows, which in this area are boggy due to spring waters. Below the meadow com- plex, there is a timber bridge, and below it CONCLUSIONS the river slope increases. The river fl ows through a ravine with very steep, often un- Data obtained from the mapping of the dercut banks, grown over with alder, willow channels of both the investigated rivers in- and osier. There are numerous springs in dicate that they are in a stage of dynamic the lower part of the slopes. Many obsta- equilibrium, and that they have adapted to cles, in the form of tree trunks, and piles of the conditions which arose as a result of branches are present in the channel, which 19th and 20th-century hydrotechnic inger- serve to slow down the water fl ow. About ence. This state is not disturbed even by al- 400 m below the timber bridge in the river most extreme hydrological events, such as channel there is a nearly destroyed stage of those recorded in the19th century (e.g. Feb- fall (km 31.65). Below, towards the rail- ruary 2005). Lately, the most intense side way bridge, the river fl ows in a widening erosion has been observed on the Wieprza and an increasingly shallow bed of natural above and below the outlet of Broczynka, character, which in some places inundates below the connection with Pokrzywna, be- the bottom of the valley. Sandbars often ap- low the destroyed reinforced concrete weir pear both under and above the water, which at Bożanka, and on the stretch between km are strengthened by turf, blocks caused by 108 and Grądki Dolne (formerly Flisów), plants, and traces of fl ow outside the river and also below the dams at Biesowice channel. In the past a water mill named (Fig. 5) and Kępice. Also on the Studnica “Młyn Lipowy” [Linden Water Mill] was lo- there are only a few, rather short stretches on cated on this stretch. Its remnants are a rela- which side erosion can be observed. Besides tively well preserved concrete bridge and a the maladjustment of the material forming destroyed concrete weir. Below, the river the river banks (mostly non-cohesive sand) slightly reduces its slope and fl ows through to the present hydrodynamic conditions, the boggy and overgrown areas with bushes, main reason for the erosion is the reduction which replaced the small wet meadows that of the sediment load, which accumulates in had previously grown here. A small un- the reservoirs of the hydropower plants, and

http://rcin.org.pl 36 Wacław Florek, Jolanta Jaromij, Magdalena Skwierawska in the local increase of the river slope as – inundating those areas close to the reser- a result of the regulating (straightening) of voirs (fragments of the fl oodplain). the river at the beginning of the 20th century. For several decades there have been no Lower order causes, which have a local im- works that have interfered with the river pact, may be considered, such as the pres- channel (except short stretches at the dams ence of various obstacles in the river chan- and weirs, in settlements and by bridges; nel, mainly fallen trees, which change the e.g. the re-commissioning of the weir at local conditions of the water fl ow. Kępka, the fi lling of washouts at Kępice in It is also worth noting that besides the 1977, the cleaning of banks such as at Ko- stretches where the water level is increased rzybie in 2002), and as a consequence of by weirs and dams, the accumulation of this the bed of the Wieprza is returning to mostly coarse material can be observed at its original character. Adaptation processes the outlets of all the larger tributaries into manifest themselves in various ways, in- the Wieprza River (and also the Studnica). cluding relatively strong lateral erosion (the A greater, more extensive infl uence on rate of side displacement of concave banks the functioning of the river channels of the of meanders in the years 1838-1938 was lo- upper Wieprza and Studnica was, and still cally 4 m/year) and by the gradual lifting is, exerted by the reservoirs of hydropower of the bottom, especially on the stretch be- plants. Their infl uence manifests itself in tween Korzybie and Sławno. However, it the following ways: should be noted that there are only a few – reducing the water velocity above the stretches with intense bank erosion and damming facilities, and its strong differ- their length is small, except the stretches entiation within the reservoirs, below the hydropower plants at Biesowice, – the increasing the accumulation of coarse Kępka and Kępice. At the same time, the material (bed load material), and in zones banks are gradually becoming overgrown where fl ow velocities are signifi cantly and the river channel is becoming increas- reduced the accumulation of suspended ingly blocked by fallen trees. matter (including material that originated Taking into account that the stretch be- in sewers) can also be observed. This re- tween Biesowice and Korzybie is within the sults in the fermentation of sediments, Protected Landscape Park “Lake Łętowskie a disturbance of oxygen management and and Kępice Area”, and that along its whole the eutrophication of the reservoirs, length the Wieprza valley fulfi ls the func- – in the Biesowice plant’s reservoir, over the tion of an ecological corridor, and also be- course of several decades of normal accu- cause there are plans to create a Landscape mulation of the sand and gravel fraction, Park, “the Wieprza and Studnica Valley”, a classic “Gilbert” type delta was formed, the present state can be considered to be which now reaches nearly over the whole both advantageous and desirable. of the reservoir, including the part lead- ing directly to the turbine inlet. The bot- tom surface, on top of which coarse frac- REFERENCES tions are transported, has now been lifted nearly to the level of the turbine intake. In Ekspertyza hydrologiczno-przyrodnicza effect, functionally, the part of the reser- zlewni rzeki Wieprzy (1957), Biuro Pro- voir closest to the dam has changed from jektowe Wodno-Melioracyjne, Oddział a zone of accumulation to a transit zone, w Poznaniu, Pracownia w Słupsku, ma- szynopis w Archiwum Urzędu Melioracji

http://rcin.org.pl Hydrotechnic structures on the Pomeranian rivers... 37

Wodnych w Gdańsku [The hydrologic- Lindmajer, J. (1999), Rzeki na terenie rejen- environmental expertise of the river Wie- cji Koszalińskiej jako szlaki transportu prza drainage area, 1957. Water-Drainage towarowego w okresie od połowy lat Project Offi ce, Department in Poznań, czterdziestych do połowy lat sześćdzie- Laboratorium in Słupsk, typescript in siątych XIX wieku [Rivers in the Kosza- the Archives of Waterdrainage Offi ce in lin Province zone as shipment track in Gdańsk]. period from the half of the 40’s until the Florek, E. (2001), System energetyczny rze- half of the 60’s of XIX century], Przegląd ki a przekształcenia rzeźby doliny Słupi Zachodniopomorski 14, 2, 103-110. [Large-scaled anthropogenic transfor- Operat wodno-prawny elektrowni wod- mations of land relief in the Słupia Val- nej w Biesowicach (1986), maszynopis ley – hydropower system of the River], w Archiwum ZEW „Enwod” w Słup- in E. Gerstmannowa (ed.), Materiały sku [Water-legal documentation for the do monografi i przyrodniczej Regionu hydro-electric power plant at Biesowice Gdańskiego [Monography of the (1986), typescript in the Archives of Gdańsk Region environment], volume 5, ZEW „Enwood” in Słupsk]. Wydawnictwo Gdańskie, Gdańsk, 51-58. Rachocki, A. (1974), Przebieg i natężenie Florek, W. (1991), Postglacjalny rozwój współczesnych procesów rzecznych dolin rzek środkowej części północnego w korycie Raduni [Course and intensity skłonu Pomorza [Postglacial develop- of present-day fl uvial processes in the ment of river valleys in the middle part of Radunia River as an example], Doku- the northern slope of Pomerania], Wyższa mentacja Geografi czna 4, Instytut Geo- Szkoła Pedagogiczna w Słupsku, Słupsk. grafi i i Przestrzennego Zagospodarowa- Florek, W., Nadaczna E. (1986), Zmiany nia (IGiPZ) PAN. biegu Parsęty i Wieprzy w ciągu ostatnich Rocznik Hydrologiczny Wód Powierzchnio- dwustu lat w świetle analizy materiałów wych. Dorzecze Odry i rzek Przymorza kartografi cznych [Changes in the course pomiędzy Odrą i Wisłą, rok 1983 (i star- of the Parsęta and Wieprza rivers, North- sze) [Hydrologic Yearbook of Surface ern Pomerania (Poland) in the last 200 Waters. The Odra River catchment as years in the light of cartographic material well as the catchments of the rivers ly- analysis], Badania Fizjografi czne nad ing between the Odra and , the Polską Zachodnią 36A, 33-52. 1983 yearbook (and earlier ones], Insty- Lindmajer, J. (1997), Przyczynek do mono- tut Meteorologii i Gospodarki Wodnej, grafi i małych rzek Pomorza Zachodnie- Warszawa. go na przykładzie Wieprzy w trzecim Sylwestrzak, J. (ed.) (1977) Pojezierze By- ćwierćwieczu XIX stulecia [The contri- towskie. Monografi a geografi czno-eko- bution to the monograph of small rivers nomiczna [The Bytowskie Lakeland. The of the on the exam- economic-geographical monography], ple of Wieprza River in the last 25 years Ossolineum, Gdańsk. of XIX century], Rocznik Koszaliński, 35-53.

http://rcin.org.pl