Problems and Water-Ecological Risks of Site Development on the Drained Lands of an Old Floodplain of the Dnieper River

Abstract

Relevance of research. In recent years, in Ukraine, the development of re-cultivated drained lands takes place, in particular, in the floodplains of the rivers. In the process of construction, drainage systems designed to protect agricultural land and adjoining areas against flooding are often disrupted. In addition, peat and silt deposits may be spread in the floodplain areas, which considerably complicate the construction. The transformation of agricultural drained lands of floodplains in the built-up areas is also associated with an increased risk of flooding, contamination of surface and groundwater, and requires compliance with environmental, water and land legislation. In this regard, an important issue is the study of water and environmental problems connected to the build-up of the land of reclamation systems in floodplains of rivers.
 The purpose of research - to identify possible water and ecological impacts and restrictions as to the development of drained lands within an floodplain of the Dnieper River.
 Objectives of the research - to analyze the available information on the geomorphological, hydrological and hydrogeological conditions of the floodplain territory; to evaluate the condition of the drainage system at the perspective site development; to determine possible changes in the water regime of the floodplain area in the zone of development impact; to evaluate the soil and ameliorate conditions of the territory with regard to its possible use for development and the compliance of the planned design solutions with the requirements of land and water legislation.
 Research methods. Generalization and systematic analysis of the information on the natural conditions of the territory and drainage system operation, carrying out of a reconnaissance survey of the drainage system specifying with the use of temporary well holes the peat deposit thickness, depths of groundwater, water level in reclamation canals and their current state, the implementation of field geodetic works, normative assessment of soil and ameliorative as well as engineering and geological conditions of the site as to its for development.
 Research results. The features of the current environmental and ameliorative situation regarding the possible obstacles to the housing complex construction and its further functioning, the likely or inevitable negative consequences of the floodplain development were determined. It was established that the existence of closed depressions in the microrelief against the background of the general low draining capacity of the floodplain territory, in case of extremely heavy rainfall, may cause the accumulation of surface runoff in the depressions and territory flooding. High groundwater level, deterioration of draining capacity, destruction of drainage drains during the construction will lead to the proliferation and intensification of man-made flooding processes in poorly-drained areas.
 One of the most complicating factors in the construction of the site is the wide spread of peat deposits, peat soils, silt, which, according to the general engineering and geological classification, are “weak” soils characterized by low bearing properties and can not be recommended as a basis for the foundations of ground structures and buildings. It has been determined that the existing “Shaparnya” drainage system is in unsatisfactory technical condition, and its parameters (rather low depth of drainage canal laying and a large distance between them) make it impossible to achieve the normative depths of groundwater for built-up areas.
 Conclusions. The area of ​​weakly drained floodplain of the Dnieper River can be differentiated into weakly favorable and unfavorable parts for the construction of the territory, and the main complicating factors for the construction are the spread of peat deposits and peat soils, frequent underflooding of the territory and the risk of its flooding in a case of abnormal heavy high rainfall. The proper protection of the territory of residential development against underflooding and flooding should include the reconstruction of the drainage system, artificial increase of planning ground levels and ensuring the safe functioning of the existing at the site water body.

The influence of deep loosening on the ecological and meliorational state of drained mineral soils

“…According to the results of predictive and simulation modeling using the appropriate set of models [4,10], the effectiveness of the application of improved continuous loosening of the soil during the growing season was determined. This was carried out in combination with various methods of water regulation of drained mineral soils on the example of the studied object (soilsandy loam, area -10 ha, cultivated crop -perennial grasses for hay) for the estimated dry growing season under the conditions of heat and moisture supply (p = 70%).…”

“…According to the obtained experimental results, predictive calculations were made based on the use of an appropriate complex of forecasting and simulation models, which includes a local climate model, models of the water regime and water regulation technologies of drained lands, a model of the development and formation of the crop of cultivated crops, which are implemented on the basis of a long-term forecast [4].…”

“…For an approximate assessment of the ecological sustainability of the researched measures, the degree of consideration of the factors of ecological reliability of their operation and to maintain favorable natural and reclamation and soil regimes within the project term, the calculation of the coefficient of ecological reliability (k n ) of the operation of the reclamation system was carried out based on the set of relevant physical indicators of ecological efficiency (indicators water regime, indicators of salt regime and productivity of drained lands). The ecologically optimal option is considered to be the one for which the coefficient of ecological reliability is in the interval of values k n = 0.5...1.0, in addition, the coefficient of ecological reliability indirectly reflects the ecological and melioration state of drained mineral soils [4].…”