Knowledge of properties of materials deposited in beds of small reservoirs is important, as it can be used for a range of analytic works, concerning river rehabilitation and river management and other similar undertakings. Usually the one property - the d50 value can be obtained using in-situ measurements using sieves but in most cases of preliminary, large scale research may not be feasible. In this paper the Osuch empirical formula for determination of standard sediment grain sizes of d50 is presented. Besides the original formula an improved method of assessing of the slope value for that formula is proposed, which may greatly improve the usefulness of the original, unmodified method. The calculation results are then compared with the in-situ measurements done on many samples taken from the Trzebuńka dam reservoir. The dam was recently partially removed and partially rebuilt, so there was an unique and easy access to wide strata of different layers of sediments, accumulated across many years of dam operation in the exposed bed of partially emptied reservoir. Additionally, the Ratomski formula for riverbed slope determination near dams was used as a reference. The mentioned methods taken together can be used for preliminary analysis before significant ...
A check dam is a hydraulic structure, which is constructed in order to limit river sediment transport. A sedimentation reservoir is created upstream from the body of the dam, where river sediment is constantlyaccumulated. These structures were constructed starting in the early 20th century in upstream parts of mountain streams in the Polish part of the Carpathian Mountains. At present, the reservoirs of most check dams are already fully filled with sediment and the impact of these structures on the ecosystems of streams is unfavorable. Moreover, the dams that have not been renovated are in poor technical condition. In the paper two cases of check dam lowering and restored is discussed and the one hypothetical case of gradual check dam lowering is presented and discussed as well. The cases of Krzczonówka and Trzebuńka, where the method ofremoving sediment from reservoirs was different, showed that the sudden change of „established" hydrodynamic conditions for decades is not favorable for the stream. The results of hypothetic simulation of gradual check dam lowering for the case of Isepnica Stream leads to the conclusion that lowering the construction of check dam and removing sediment from its reservoir in a way that does not have a ...
