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The rivers of the Gaspé Peninsula, Québec (Canada), a coastal drainage system of the St. Lawrence River, receive and transport vast quantities of large wood. The rapid rate of channel shifting caused by high-energy flows and noncohesive banks allows wood recruitment that in turn greatly influences river dynamics. The delta of the Saint-Jean River has accumulated wood since 1960, leading to frequent avulsions over that time period. The wood raft there is now more than 3-km in length, which is unusual but natural. This jam configuration allows a unique opportunity to estimate a wood budget at the scale of a long river corridor and to better understand the dynamics of large wood (LW) in rivers. A wood budget includes the evaluation of wood volumes (i) produced by bank erosion (input), (ii) still in transit in the river corridor (deposited on sand bars or channel edges), and (iii) accumulated in the delta (output). The budget is based on an analysis of aerial photos dating back to 1963 as well as surveys carried out in 2010, all of which were used to locate and describe large wood accumulations along a 60-km river section. The main results of this paper show that the raft formation in the delta is dynamic and can be massive, but it is a natural process. Considering the estimated wood volume trapped in the delta from 1963 to 2013 (≈ 25,000 m 3 ), two important points are revealed by the quantification of the wood recruitment volume from 1963 to 2004 (≈ 27,000 m 3 ± 400 m 3 ) and of the wood volume stored on the bars in 2010 (≈ 5950 m 3 ). First, the recruitment of large wood from lateral migration for the 40-year period can account for the volume of large wood in the delta and in transit. Second, the excess wood volume produced by lateral migration and avulsion represents a minimum estimation of the large wood trapped on the floodplain owing to wood volume that has decomposed and large wood that exited the river system. Rafts are major trapping structures that provide good potential sites to monitor wood delivery from the catchment through time and allow estimations of LW residence time while in transit. These results contribute to understanding the interannual large wood dynamics in the Saint-Jean River and can assist river managers in determining sustainable solutions for coping with the issue of wood rafts in rivers. [ABSTRACT FROM AUTHOR]

The Watershed Analysis Risk Management Framework (WARMF) model is adapted to simulate flow and nitrate-N transport in an agricultural watershed in Quebec, Canada. The model was evaluated for the St. Esprit Watershed (24.3 km²), which is a part of the 210 km² St. Esprit river basin, a tributary of the L'Assomption Watershed (4,220 km²). WARMF's hydrologic calibration and validation was performed using data from the gauge station located at the outlet of the watershed. Water-quality data collected were used to guide water quality calibration/validation. Simulations were carried out from 1994 to 1996; data from 1994 and 1995 were used for model calibration and data from 1996 were used for model validation. The model performed reasonably well in simulating the hydrologic response and nitrate losses at the outlet of the watershed. The R² between the observed and simulated monthly stream flow for calibration was 0.92, and that for validation was 0.94. The corresponding coefficients of efficiency (E) were 0.89 and 0.91. The R² and E values for calibration/validation of NO3--N loads simulation were 0.89/0.84 and 0.86/0.75, respectively. Thus, the model simulated monthly flow and nitrogen losses with a good degree of accuracy over the entire year. [ABSTRACT FROM AUTHOR]