FORMING AND DISAPPEARANCE OF SMALL RETENTION SYSTEM IN THE POSTINDUSTRIAL AREA – CASE STUDY FROM THE CENTRAL SECTION OF THE KAMIONKA RIVER VALLEY (CENTRAL POLAND) SINCE THE 18TH CENTURY

The Kamionka Valley is an old industrial area located in the northern part of the Świętokrzyskie Province. From the early Middle Ages was mined here iron ore and processed in forges located on the river. Many forges was operating also in Suchedniów located in middle section of the river. For over the last centuries, in this area the river have been occurred many anthropogenic changes related to human impact. Industry, based on mining and metallurgy, developed here as part of the Old Polish Industrial District and the Central Industrial District. Their activities contributed to numerous changes in the riverbed and the construction of water reservoirs creating system of small retention in Kamionka. Most changes on the river took place in time of high activity of the forges (from 18th to the first half of the 20th century). Changes in industrial activity reduce the number of ponds on the river led to an increased risk of flash floods, which perfectly illustrates the events taking place downstream of the Suchedniów reservoir dam (1974 and 2010).


INTRODUCTION
The Kamionka river valley is located in the northern part of the Świętokrzyskie Province. Iron ore was mined here from the early Middle Ages, which was processed in forges. Those forges was operating also in Suchedniów town located in middle section of the river. Kamionka is the right tributary of Kamienna river. The entire catchment area is located on the Suchedniów Plateau. Kamionka is a meandering river with a length about 17 km and an average slope 5 o /oo [1]. During the last centuries, in its middle section of the river there have been occurred many anthropogenic changes related to industrial activity. Industry, based on mining and metallurgy, developed here as part of the Old Polish Industrial District and then Central Industrial District. Suchedniów was established here as a small settlement. First historical data of it come from years 1224 [2] and from 1510 come first information about the forge operating on the river [3]. Their activities contributed to numerous changes in the riverbed and the construction of water reservoirs creating system of small retention in Kamionka basin. At the turn of the 19 th and 20 th century, the forges on Kamionka river were abandoned. In their place was built water mills using old hydrotechnical infrastructure. To the half of the 20 th century numerous small ponds were drained and replaced with larger reservoirs for retention purposes. The further expansion of the city contributed to regulating the riverbed which resulted in the disappearance of the flood plain on some sections of Kamionka river valley (just like downstream of the Suchedniów reservoir dam). Changes in the water cycle in the Kamionka river basin introduced by man led to the emergence of new catastrophic events on the river.

AIM OF THE STUDY AND METHODS
The article focuses on the analysis of anthropogenic changes at Kamionka and their impact on the development of the Suchedniów area in recent centuries. An analysis of archival materials (old topographical maps, Suchedniów situational plans, photographs) were compared with the results of the field observations of the studied area. There were used maps and archival materials from the 18 th century (some of information are from 16 th century) to the first half of the 20 th century. A large part of these materials comes from private collections of the people living in Suchedniów, as well as from the "Suchedniów Lexicon" [3]. The results of these studies have allowed the location of former hydrotechnical objects and their remnants on Kamionka river in this area. Also was made an analysis of modern hydrotechnical facilities in Suchedniów and their impact on the development of the city. In 2017 there was begin a works leading to deepening reservoir in the Suchedniów. In fact this moment was used to made extensive analysis of forms and sediments of this hydrotechnical object.

HISTORICAL CHANGES
Since Prehistoric times, and later in the Middle Ages, mining and metallurgy based on iron ore, which lies in the Triassic deposits, played an important role in the development of this area. To the west of the investigated area developed Prehistoric metallurgy using furnances known as bloomerys [4]. The first information of forges operating in the Suchedniów area came from the beginning of the 16 th century [3]. On Kamionka river at that time there were at least 7 forges [5]. Those forges use Kamionka river as proper source of energy. The processed iron ore came from mines located in nearby hills where are until today preserved many buried mining shafts. Local forests were also used as a source of charcoal, which were burned in the forges. Suchedniów was a large mining and industrial center. The industrial and urban infrastructure was modernized by Stanisław Staszic [3]. Numerous embankments, channels, dams and ponds were built, which were an integral part of the infrastructure of the forges [5], [6]. The remains of the old infrastructure of those forges are still clearly visible in the center of Suchedniów (dry channel or ground shaft near the city park). Created ponds near of the old forges have not been preserved to this day, but they are clearly visible on topographic maps from the turn of the 18 th and 19 th century (First Military Survey 1763-1787 -West Gallizien 1801-1804) (Fig. 1). These reservoirs are also visible on many other sheets from later years, as well as on old photographs and town plans. Archival materials document the dynamics of changes taking place during the last centuries on Kamionka river. They show, among others formation and disappearance of the Suchedniów water reservoir [1] (Fig. 2). In 1863, as a result of insurgent actions, Suchedniów was completely burnt by the Muscovites. However, the hydrotechnical infrastructure of forges and mills was quickly rebuilt. The forges was used until the end of the 19 th century. Some of water mills was using remaining hydrotechnical infrastructure of old forges. To the half of the 20 th century water mills were no longer used in this area. This meant that up to the middle of the 20 th century, many smaller ponds in Kamionka disappeared. In modern times most of the mills have been destroyed (Baranów), while the rest have been restored (Berezów and Jędrów).

PRESENT-DAY CHANGES
In the second half of the 20 th century, many water mills were abandoned or dismantled, and nearby ponds were drained. The traces of the former hydrotechnical infrastructure (shafts, channels, foundations of mills and forges) remained visible in the relief and landscape. Sometimes in the place of old forges was build later a larger factories (e.g. at Suchedniów). This action lead to the disappearance of small watercourses, just like Pstrążnica, small left-side tributary of Kamionka river [7], [8], [9]. North of Suchedniów, there is also a embankment of a 19 th century narrow-gauge railway, which was transported iron ore from the nearby mines and wood to the sawmill [3]. Currently, the track has been disassemble and the remaining embankment separates the flood plain into two parts. In the places where forges and mills was working on the river forming anthropogenic anastomoses as a result of industrial activity in the Kamionka. In such sections the river flows simultaneously with a natural channel and at least one anthropogenic channel (e.g. at Baranów) [10]. These anastomoses also functioned in historical times, that is visible in archival maps from last centuries. This type of river bed development also occurs on many other rivers of the Old Polish Industrial District, e.g. on the Wierna Rzeka [11]. In the second half of 20 th century the small typical industrial ponds were abandoned for the benefit of larger retention and touristic reservoirs purposes, e.g. the reservoir built in 1974 at Suchedniów and at Rejów. In 2005, the course of the river was changed near the campsite at the Sports and Recreation Center in Suchedniów.
A several-hundred-meter-long channel was dug, which Kamionka flows into the reservoir, and the natural riverbed section has been buried. Present-day there is a small haven in the former estuary [1]. The current hydrotechnical infrastructure on Kamionka does not provide full retention possibilities. This led to the occurrence of sudden catastrophic events on the river, such as flash floods. They took place, for example in the Rejów reservoir in 1939 [12] as well in Suchedniów in 1974 [3], [13]. Shortly after completion of the construction works of the Suchedniów reservoir due to the overfilling of it, the shaft was broken near the dam. This lead to create a flood wave on the river downstream from the reservoir. The traces of these floods are visible on a short section of river downstream of the reservoir, where is accumulated the coarsest material (rocks, concrete fragments, sandstone pebbles) [14]. [15]. Recent research confirms the lowering of the retention functions of the reservoir due to its silting and shallowing. This was caused, among others, by construction of the S7 expressway, of which embankments were incised by Kamionka. This led to the include a large amount of material into river transport, which was accumulated in the reservoir at Suchedniów. The result of this process was the formation of a clear inland delta at the estuary of the river into the reservoir [16], [17]. Decreasing the flood potential of the Suchedniów reservoir lead to the occurrence of further catastrophic events [1]. In 2017 started works lead to deepen the reservoir at Suchedniów. The aim of this work is to restore the reservoir's retention capabilities by sediments dredging from its bottom, removing deposits, creating new reservoir slopes and repairing the dam. The moment when reservoir become dry gave the opportunity to start research on the sediments and forms accumulated from the beginning of its existence. During this work was discovered remains of the previous reservoir (probably from the beginning of the 20th century) as the distinct, dark layer of muds. This material was covered by 1.0-1.5 m diameter, sandy mega ripple marks left by the flood caused by the breaking of the dam in 1974. All those layers are covered with sediment deposits of the modern reservoir.

CONCLUSIONS
The presented area perfectly presents the high level of anthropogenic changes on the river caused by industrial activity. Most changes are visible near the Kamionka riverbed in the Suchedniów area. Mining and metallurgical activities within the Old Polish and Central Industrial Districts contributed to the creation of many water mill ponds on Kamionka river.
Most changes on the river took place from the 18th to the first half of the 20th century, when most metallurgical plants and water mills were active in here. Kamionka was regulated, especially in the middle section, as a result of the construction of many channels, reservoirs and a change in the direction of the river's flow. Human activity on the river contributed to the formation of anthropogenic anastomoses, functioning in historical times, and locally also in modern times.
Reducing the number of ponds on the river led to an increased risk of flash floods, which perfectly illustrates the events taking place downstream from the dam in Suchedniów reservoir (1974 and 2010). Present-day, various investments are being carried out in Suchedniów on Kamionka to improve the hydroelectric infrastructure possibilities, as well as their tourist assets. These investments also enabled the discover in the sediments the old ponds remains. These discoveries confirms the disappearance of small retention which appear on many cartographic materials from the last centuries.