Technical sciences / 2. Mechanics

Ph.D., Gnativ¹ R.M., ph.D., Yakhno² O.M., Gnativ¹ I.R.

1- NU "Lviv Polytechnic", Lviv, Ukraine

2- NTUU "Kiev Polytechnic Institute", Kyiv, Ukraine

Influence of quarrying on the change of longitudinal profiles in the mainstream of the river Stryi

Stryi River basin is one of the most favorable territory in the Western Ukraine in the ecological means, but anthropogenic processes influence on the geochemical conditions and the environment. The reason for this is that the resources of the territory, such as soil, mountain landscapes, mineral resources and natural water are extensively used in economic activity.

The quarries of rubble stone, gravel and gravel-pebble mixture influence on the modern geochemical conditions of the Stryi River Basin. Gravel-pebble and boulder deposits in the mainstream of the river have a lot of important geo-ecological functions. They regulate the speed of streamflow in the mountainous part of the basin, in areas with significant obliquelys in the range of 2 to 4 m / s, increase the roughness of the bottom, level and differences of heights in the profile of the watercourse that are caused by the geological structure. It is quite clear that uncontrolled selection of the resources of alluvial gravel and pebble sediments in the river basin Striy can be the first cause of extremely negative impact on the natural waters. The result of such influence in flood-inundation periods are technologically-accelerated riverbed changes and deformation and potential deterioration of the quality of natural waters.

Steady location of sand and gravel sediments in the mainstream, floodplain and terraces above the floodplain is a marker of the fixed local base of channel erosion [1]. Floodplain sediments are constantly updated and supplemented, they migrate and change the direction of flow within the floodplain due to their transference downstream from the mountainous part of the basin. Within the Ciscarpathia these sediments are the aquifer of the unique Stryi groundwater deposits with the depth up to 20 m, that provide his significant reserves and high quality of the water.

Intensive career selections of sand and gravel material have in the mainstreams discrete character and different length. Levelling of the river bottom are made by some further floods and expenses that are capable to deform the channel, that are called channelforming.

Extraction of gravel and pebble sediments, that are often realized on the pretext of clearing the river beds, eliminate sediment and islands in order to prevent the negative impact of the passage of floods is not always justified on geo-ecological side. In practice, such activity leads not only to a decrease in the local base of erosion, destruction of the banks and the deterioration of water quality, but also adversely affects the spawning migration and fish spawning in the Striy river basin. Recently is observed a significant volumes increase of quarry exploration in the rivers basin of Ukraine (picture 1).

Especially dangerous for the quality of natural waters is uncontrolled taking off of the channel deposits. The volume of unaccounted mining of the gravel-pebble mixture up to 20 times exceed their introduction from the upper sections of the basin. Uncontrolled mining leads to disruption of the surface layer of the channel bed, causes sharp decrease of the river bed resistance degree to the growth of erosion processes, increases the speed of conversion of microelements in the soluble form. It affects especially negative the natural water quality of river basin.

It is established that the active taking off of the soil from the river beds quarries leads to decrease in the levels and consequently to increase in inclinations and speeds of water flow. The feature of the speed longitudinal distribution above the quarry excavation is a reduction of the speed average from upriver slope to the central part of the quarry and increase - to the downstream. The ratio of average speeds on typical quarry areas at different periods of their development are 0,68-1,10. Extraction of sand and gravel in the river bank area of the leads to the formation of water eddy zones width of 20-30 meters with flow speeds within 0,04-0,11 m / s. On the line of such eddy zones and transit flow are a formed unstable deposit, which depends on the depth of the stream. Due to the significant change in the riverbed morphology above the quarry section occurs displacement of the dynamic axis of flow from the left bank to the middle of the river of the value 0,25-0,3 its width.

Pic. 1. Dynamics of extraction of gravel- pebbles mixture in the rivers basin [2]

It is established, based on experimental studies, that the extraction of sand-gravel mixtures and building of the structures, correcting the river beds, has serious negative consequences, first of all - the lack of alluvions below the quarries, infringement of the kinematic structure of the flow, that affects the water quality.

Литература:

1. Явкін В. Розвиток базису ерозії басейнів Прута, Черемоша та Сірету/ В. Явкін, А. Кирилюк, М. Цепенда//Річкові долини. Природа-ландшафти-людина. Збірник наукових праць. - Чернівці: Рута, 2007. - С. 258-266.

2. Мінеральні ресурси України /ДНВП “Державнийінформаційний геологічний фонд україни ”.- Київ, 2014.- 270с.