Peak flow responses to strip thinning in a nested, forested headwater catchment

Abstract

Abstract:We evaluated the effects of 50% strip thinning on peak flow responses in 17-ha and 9-ha nested catchments. We observed 117 storm events from April 2010 to December 2013, including 32 events in the pre-thinning period, 15 events during the thinning operation, and 70 events in the post-thinning period. Paired-catchment analysis with multiple pairs of nested gauging stations revealed that changes in peak flow responses varied depending on the location of the nested observation stations. Increases in peak flow during the operation period were significant in gauging stations located at the outlet and the middle of a catchment. Increases in peak flow during the post-treatment period became significant in all nested catchments, but not in the catchment outlet. Rates of increase in peak flow ranged from 17.7% to 44.4%, which is within the range of previous studies. Different responses for changes in peak flow among nested pairs were associated with changes in internal hydrological flow pathways due to removal of timber and hydrological connectivity via overland flow generated by newly installed and reactivated skid trails. Our findings suggest that the effects of timber harvesting on peak flow are scale-dependent with respect to drainage areas, hydrological links, and management practices. Selection of gauging locations and process-based observations within catchments are essential for testing hypotheses related to the effects of timber harvesting with robust hydrological monitoring.

Effect of tree thinning and skidding trails on hydrological connectivity in two Japanese forest catchments

“…However, Dung et al (2015) found different hydrological responses among nested catchments caused by changes of hydrological connectivity via overland flow generated by newly installed and reactivated skidding trails. Skidding trails and forest roads can play roles of sediment source and pathway for runoff and sediment, from forest floor to stream channel (Mizugaki et al, 2008).…”

“…The two subcatchments have been extensively described elsewhere (Kato et al, 2012;Sun et al, 2014a, b andc, 2015a andDung et al, 2015), and a summary is provided below. Two hillslope plots were installed in the cypress plantation of the K2 SubC, named KS22 and KS24, Geomorphology, DOI: 10.1016/j.geomorph.2017 López-Vicente et al, 2017 -Hydrological connectivity in two Japanese forest catchments and one plot in the cedar plantation, named KS31 (Fig.…”

“…Discharge was measured using a combination of Parshall flumes and box-type V-notch weirs. Data was recorded at 5-min intervals, and daily values calculated afterward (more details in Dung et al, 2015). As FMO caused topographic changes because of the construction of new skidding trails in the hillslopes, three airborne surveys were conducted in order to acquire an accurate DEM of the study area at each scenario.…”

Influence of strip thinning on nutrient outflow concentrations from plantation forested watersheds

“…The subcatchment areas for K21, K22, K23, K24, K31 and K32 were 15.1, 6.6, 4.1, 2.6, 8.5, and 2.9 ha, respectively. Paired‐catchment analysis was applied to these basins on the basis of their runoff characteristics observed before the thinning (Dung et al , ). In addition, the patterns of discharge and nutrient concentrations were similar during this period (K21 and K31 in Figure and others in Supplementary Figure 1).…”

Catchment based hydrology under post farmland abandonment scenarios

“…However, abandonment of these terraces can generate concentrated runoff and sediment flows along preferential pathways created by the successive collapse of several terraces, promoting connections between these pathways and the main stream network (Calsamiglia et al, 2017). Changes in connectivity can explain changes in catchment runoff response and sediment yield (Meerkerk et al, 2009;López-Vicente et al, 2013a;Dung et al, 2015). Thus, a general decrease in connectivity is expected to reduce streamflow and sediment discharge.…”