Stream channel changes as a result of sudden sediment release due to check dam lowering (Polish Carpathians)

Abstract

Channel response to dam removal is still poorly understood, as there is a lack of monitoring data. A small dam in the gravel bed Krzczonówka Stream was lowered in 2014 as the first in the Polish Carpathians. The paper describes the direction and magnitude of channel changes after the check dam lowering against the backdrop of slow changes in the riverbed occurring over a period of several decades. Geomorphologic mapping and geodetic measurements started in 2013 and were repeated in 2014. Archived cartographic sources were used to identify channel morphology in the past. After the studied check dam had been partially lowered, a flood occurred and caused movement of sediment from the reservoir into the channel downstream. Debris filled pools and artificial riffles were created in 2013-the largest deposition occurred just below the dam. The channel width also increased in this area. The channel reach upstream from the dam was incised. Additional gravel supply is limited because of a sequence of drop structures just upstream of the studied reach. Long-term channel evolution after dam lowering depends on flood events and the availability of material for fluvial transport.

Erosion Process of Multiple Debris Flow Surges Caused by Check Dam Removal: An Experimental Study

“…In terms of the method for removing check dams, this research mainly focused on the removed height. In addition to partial removal (Korpak & Lenar‐Matyas, 2019), staged removal has been performed for many check dams (Ibisate et al., 2016), and in check dam groups, an investigation of the appropriate removal sequence was necessary (Collins et al., 2017). Further research on the staged removal and removal sequence of a dam group is of great significance to engineering practice.…”

“…After incision to the base level and widening, further erosion depends on large floods (Collins et al., 2017). From the perspective of sediment transport, the process can also be divided into a transport‐limited stage and a supply limited stage (East et al., 2018; Korpak & Lenar‐Matyas, 2019). Factors such as grain size, levels of cohesion and consolidation, spatial variability of the deposit, deposit geometry, and removal timeline determined the rate and volume of sediment erosion (Doyle et al., 2003; Ibisate et al., 2016; Mergili et al., 2020; Sawaske & Freyberg, 2012), and an exponential function describing the evolution of the sediment erosion volume was verified based on field observation data (Collins et al., 2017; Pearson et al., 2011).…”

Reuse of a dam as sediment trap and water reserve

“…As such, much of the sediment already stabilized in the reservoir, in addition to that which is seasonally added, will be transported downstream. In the worst-case scenario, with dam removal, the impact of sediment remobilization will increase and become permanent (Korpak & Lenar-Matyas, 2019), intensifying the silting up process in the Pantanal wetland of the Pandeiros River.…”

Hydrological simulation and assessment of the optimal parameters of the water replenishment of the floodplain lake and old riverbed on the Uzh river

“…The too modified riverbed situated in the city is almost impossible to restore to its natural state due to the significant changes in the environment state and the absence of the free space for natural regime. Thus, partial measures are often used, which depend on the communities economic capabilities: bank stabilization, clearing of the riverbeds [5], using aquatic plants and animals to clean riverbeds and floodplain lakes from anthropogenic pollution [6], expanding inter-dyke room [7,8], restoration of tortuosity and multi-sleeved channels, connection of the riverbed and the floodplain by hydraulic structures in the dykes or its destruction [9], restoration of natural regime of water and sediments [10]. In addition to economic constraints, according to the work [11] in which restoration projects in different countries were compared, the degree of river restoration is influenced by national specificity, which does not allow to develop a single ideal mechanism for assessing the effectiveness and necessary measures of the river restoration on the urban areas.…”