*Appendix A.2. Fine Sediment Accumulation during Flood Recession*

In this study, it is assumed that partial bed fluidization or erosion during falling limb of a flood event reduces the volume of porous media available for particle accumulation. For flood recession period with flow rate Q(t), Equations (A1) and (A2) are modified using the substitution β = β Qmax and applied to the model as

$$\text{bed version depth at Q(t)} \propto \exp\left[\beta \frac{\mathbf{Q(t)}}{\mathbf{Q\_{max}}}\right] \tag{A5}$$

$$\text{maximum bed region depth at } \text{Q}\_{\text{max}} \propto \exp[\beta],\tag{A6}$$

The available capacity for fine sediment storage is estimated by subtracting the bed erosion depth during flow recession at a flow rate Q(t) from the maximum bed erosion depth. Thus in the model, the available capacity for fine sediment storage in the sediment bed is represented during the falling limb of a flood event by

$$\frac{\mathbf{M}\_{\rm cap}[\mathbf{Q}(\mathbf{t})]}{\mathbf{M}\_{\rm max}} = \frac{\exp[\beta \mathbf{I}] - \exp\left[\beta \frac{\mathbf{Q}(\mathbf{t})}{\mathbf{Q}\_{\rm max}}\right]}{\exp[\beta \mathbf{I}]} = 1 - \exp\left[-\beta \left(1 - \frac{\mathbf{Q}(\mathbf{t})}{\mathbf{Q}\_{\rm max}}\right)\right] \tag{A7}$$

$$\mathcal{M}\_{\text{cap}}[\mathbf{Q}(\mathbf{t})] = \mathcal{M}\_{\text{max}}\left\{ 1 - \exp\left[ -\beta \left( 1 - \frac{\mathbf{Q}(\mathbf{t})}{\mathbf{Q}\_{\text{max}}} \right) \right] \right\},\tag{A8}$$
