Large wood load and transport in a flood‐free period within an inter‐dam reach: a decade of monitoring the Dyje River, Czech Republic

Abstract

This study examined the large wood (LW) load and transport during the non-flood period (2009-2018) following major floods that occurred in 2002 and 2006 within the inter-dam reach of the Dyje River (Czech-Austrian border). The LW load was examined in 36 river corridor segments scattered within the reach in the 2009-2018 period. Two whole-reach surveys (2011 and 2019) on LW frequency and distribution were conducted, and the export of LW to the downstream reservoir was analysed between June 2013 and December 2018. In the period of non-flood discharges, the recruitment and depletion of LW were highly variable processes in space and time, leading to a considerable change in the total LW quantity. Whereas the total number of LW pieces decreased, the total LW volume increased because of the increasing dimensions of newly recruited pieces. The annual variability in the quantity of newly recruited pieces was better explained by the variation in the maximum annual discharges (y = 41.043ln(x) + 3.2737, R 2 = 0.5352) than by the variability in the number of days with wind gusts >17.2m/s (y = 1.5004x + 82.096, R 2 = 0.118). The land use change with the abandonment of human settlements after World War II and the progressive expansion of forest was the major historical factor driving the increased recruitment of LW to the river corridor. While the 2006 (>100-year RI) flood brought approximately 1,250 LW pieces to the reservoir, the 2013 (1.5-year RI) flood delivered 45 pieces. The long-term average monthly input of LW to the reservoir was 7.7 pieces. The exceptional low-magnitude flood of 2013, which occurred at the beginning of the monitoring period, was shown to be a threshold above which the number of LW pieces that floated to the dam significantly increased.

Large Wood in Small Channels: A 20‐Year Study of Budgets and Piece Mobility in Two Redwood Streams

“…Storm discharges that occur multiple times per year and higher-magnitude 1-year recurrence interval flows were associated with entrainment and greater displacement lengths, although the higher 1-year flows had stronger effects. These results support previous assertions that lower-magnitude floods influence wood mobility (Máčka et al, 2020), although high flows are likely more effective (Kramer et al, 2017;Schenk et al, 2018;Senter et al, 2017). Our results point to the potential importance of high magnitude floods or debris flows on wood transport.…”

“…Wet windstorms were an important predictor for inputs into both the NF and SF, despite different dominant input mechanisms. In a much larger watershed in the Czech Republic (13,419 km 2 ), bankfull discharge and other high flow events best explained the variability in wood input rates compared to wind events (Máčka et al., 2020).…”

“…LW inputs to a stream reach occur via individual tree mortality and toppling; mass recruitment events such as wind storms, debris flows, and landslides; bank erosion; and beaver activity (Iroumé et al., 2020; Máčka et al., 2020; Martin & Benda, 2001; Wohl, 2017). The distance that LW is sourced from the channel varies with respect to input mechanism (e.g., between bank erosion and wind‐mediated recruitment) and tree stand age and height (Benda & Bigelow, 2014; Bragg & Kershner, 2004), and recruitment may be higher on steeper slopes relative to shallower slopes (Natural Resources Management Corporation, 2003).…”

The Evaluation of Color Spaces for Large Woody Debris Detection in Rivers Using XGBoost Algorithm

“…Additionally, the transportation and accumulation of LWD in river channels may destroy artificial river structures such as bridges and dikes, and may block the river to produce log jams, which would in turn escalate flood disasters and cause human life and property loss [12]. Henceforth, the study of LWD transport and accumulation has attracted the scientific community [13][14][15]. In Taiwan, the primary preventive measure against such disasters is to remove LWD from rivers directly.…”

Introduction to the Wood in World Rivers special issue

“…The first WWR conference focused on field studies, physical‐biotic interactions, and numerical modeling of wood recruitment to channels. These remain focal topics of riverine science research that explicitly includes the role of large wood, as illustrated by papers in this special issue examining controls on wood load and spatial distribution of wood in diverse field settings (Galia et al, 2020; Iroumé et al, 2020; Máčka et al, 2020; Picco et al, 2021; Rossetti de Paula et al, 2020) and on the geomorphic (Booth et al, 2020; Gurnell et al, 2019; Hinshaw et al, 2020; Iroumé et al, 2020; Zhang & Rutherfurd, 2020) and ecological (Ader et al, 2021; Shirey et al, 2020) effects of large wood.…”