## 6 Discussion
### Potential Replenishment of Bedload after Riprap Removal  
The recovery of bank erosion after riprap removal is a condition for the success of the second restoration objective, which is to increase local sediment supply and, thus, to contribute to slowing down the rate of channel incision or even counteracting it. In light of the lack of bank erosion at Site 1, it can be concluded that bank protection removal does not necessarily signify sediment replenishment. However, at Site 2 and despite exposure to the same flood events as Site 1, the local replenishment of bedload was made evident through channel morphology readjustments that occurred during bank erosion. Bank erosion has led to the widening of the channel from 43 m (2019) to 79 m (2022). With the widening of the channel, the local specific stream power decreased by almost 40% after the first period (P1\({}_{\rm C}\)) and by 9% after the second period (P2\({}_{\rm C}\)). However, these estimatesshould be treated with caution because they do not consider slope adjustments in relation to channel widening. Channel widening is a key factor in slowing or stopping channel incision. On the restored section of the Mur River, Austria, where post-restoration channel widening occurred due to bank erosion, shear stress significantly decreased [21]. On the Upper Drau River, Austria, the widening of the channel allowed the incision to be stopped and counterbalanced by an aggradation of the bed [66]. At Site 2, even though readjustment favoured a local decrease in channel incision, only longer-term field campaigns will be able to confirm these preliminary results. In particular, longer-term topobathymetric monitoring will be necessary to survey vertical channel bed evolution.  
Grain size analyses showed that the bank sediment reservoir offers good potential for sediment in-channel recharge. At least half of the bank sediments were composed of gravel (51%) and, to a lesser extent, cobble (4%). For period P1C, 4918 m\({}^{3}\) of gravel and 397 m\({}^{3}\) of cobble were reinjected into the channel, and for period P2C, 3137 m\({}^{3}\) of gravel and 253 m\({}^{3}\) of cobble were reinjected into the channel. However, based on only these volumes, it is difficult to predict what the future eroded volumes and contributions to sediment refill will be over the long term. The high erosion rates recorded over periods P1C and P2C were due to channel readjustments (Figure 7). Once the channel is morphologically readjusted, lower erosion rates than those recorded during the first and second periods are expected for similar flood patterns. Only when this equilibrium stage is reached can the estimate of lateral input from bank erosion be fully calculated.  
For the P3C period, a negative sediment balance between the eroded bank and the opposite point bar was observed, which indicates that some of the eroded bank sediment was transported downstream beyond the meander. The pathways and distances of sediments eroded from the bank and transported downstream are an important issue in post-restoration monitoring to better evaluate sediment trapping on the bar and potential transport downstream. For this purpose, in March 2021, sixty natural pebbles, consisting mostly of granite or basalt, according to the petrography of the Allier River, were equipped with active radio frequency identification (RFID) tags to monitor the individual movement of eroded particles from the restored bank [24; 67; 68; 69]. They were distributed in ten equidistant, i.e., 15 m, profiles along the bank. On each profile, six pebbles were equipped and inserted into the bank (10/20 cm inside the bank), distributed every 50 cm from top to bottom. A first survey in August 2022 showed that no bank erosion took place since the injection of the equipped pebbles into the riverbank.