Figure 1.7 shows in plan view a part of a sandy coast with a river outfall. Waves are assumed to approach perpendicular to the (initial straight) coastline. The river discharges a volume of water $$Q_r\ m^3/s$$ to the sea; at the same time sediment is transported by the river; say $$S_r \ m^3/yr$$. $$S_r$$ is expressed in $$m^3/yr$$ since we are looking at large morphological timescales.