Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Journal of Ecological Engineering

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Assessment of Changes in Channel Morphology in a Mountain River Regulated Using Grade Control Structures

Korpak Joanna

Journal of Ecological Engineering

2020

Vol. 21, nr 8

163--176

Grade control structures (GCSs) serve as some of the most frequently used forms of river channel regulation in the Polish Carpathians. The main purpose of such structures is to reduce the gradient of the channel and strike a balance between erosion and deposition. Despite the widespread use of GCSs, not much is known about their functioning over the long term. The aim of the study was to examine a host of changes in channel morphology in a mountain river regulated using such structures. The object of the research was the lower stretch of Biały Dunajec – a Carpathian river that follows a high mountain regime. The studied river stretch was regulated 33 years ago. The history of regulation and state of the channel immediately following regulation work were assessed using available regulation documents as well as a document on the post-construction period for the studied structures. The presentday morphology of the studied river channel was investigated via a geomorphologic survey and assessment of 22 channel cross sections. Gradual changes in morphology were analyzed using orthophotomaps from different years. Research has shown that the studied river channel is shaped by all fluvial processes. In the longitudinal profile, distinct channel zones characterized by stable tendencies were identified. The upstream zone is dominated by deposition, where the channel is flooded with debris after each high water stage, and GCSs cease to function as barriers to material transport. In the middle zone, lateral erosion plays a greater role, while in the downstream zone it is downcutting and lateral erosion. The river cuts alternately into both banks, thus damaging its regulated pathway. The role of deposition increases once again in the mouth zone of the river. The studied channel is not stable, and its morphology has changed many times over the years due to discharges much lower than design discharge. The Biały Dunajec did not conform to the parameters of its regulated pathway and aims to increase its width and sinuosity. The studied channel stretch requires ongoing financial expenditures to cover repair work.

Effect of Riffle Sequences on Discharge and Sediment Transport in a Mountain Stream

Korpak Joanna, Lenar-Matyas Anna, Łapuszek Marta, Mączałowski Andrzej

Journal of Ecological Engineering

2019

Vol. 20, nr 3

157--166

Natural riffles are formed as a result of fluvial processes in the stream channel, water flow, and sediment movement. In recent years, artificial riffles have also been constructed in order to improve the water flow and sediment transport as well as to initiate the processes that lead to the restoration of natural riffle–pool sequences. In river engineering, the utilization of artificial riffles (rapid hydraulic structures) is still in its experimental stage. Artificial riffles are studied and described in the literature on a case study basis. However, the studies on riffle sequences and their effects on stream channel evolution need to be improved. A system of artificial riffles was created in the mouth section of Krzczonówka Stream in 2013. The new riffles made the stream channel more morphologically diverse and also reduced its longitudinal slope. The check dam on the stream, located upstream of the newly formed riffles, was renovated and lowered in 2014. At this time, a flood occurred and released a large mass of sediment downstream of the check dam. Then, the sediment settled in the sections between the artificial riffles, thus covering some of them. The aim of the study was to examine the effect of the system of riffles on the changes in sediment transport and water flow in the studied stream channel. Calculations indicate that the system of riffles established downstream of the check dam has limited the movement of sediment. The sediment transport is varied throughout the studied stream course and is mostly dependent on the sediment supply.