Geographia Polonica Vol. 83 No. 1 (2010) Hydrotechnic
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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 WIEPRZA) 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, Poland 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 Pomerania. 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 Baltic Sea 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 Wac ł aw Florek, Jolanta Jaromij, MagdalenaSkwierawska JolantaJaromij, aw Florek, Table 1. Average and extreme water levels and fl ow in the Wieprza and Studnica rivers (Rocznik Hydrologiczny Wód Powierzchniowych...). Water level (cm) Flow ( m³/s) Catchment Station km Absolute Absolute Mean for Absolute Absolute Mean for Q :Q :Q Q :Q area [km²] max mean min max min maximum minimum 1956-1975 maximum minimum 1951-1975 Kwisno 102.4 96.4 217 157 170 2.68 0.31 0.86 3.11:1.0:0.38 8.87 17 IV 1970 27 VI 1966 (1966-1975) 1 IV 1979 4-14 IX 1976 Broczyna 84.1 381 150 32 51 15.8 2.02 4.29 3.68:1.0:0.47 7.8 7,8 II 1963 16,17 V 1959 (1961-1975) 19 IV 1970 18 VII 1982 (1961-1975) Korzybie 60.6 860 210 10 68 24.7 2.76 8.95 2.76:1.0:0.30 8.9 14 III 1940 10,11 X 1969 (1966-1975) 18 IV 1970 10,11 X 1969 (1961-1975) Ciecholub 200 88 120 12.7 2.25 3.89 3.26:1.0:0.58 5.49 (Studnica) 18 I 1982 2-4, 7 VI 1978 (1974-1983) 5 I 1982 10 VII, 15 VIII, 3 IX 1975 http://rcin.org.pl Hydrotechnic structures on the Pomeranian rivers..