You actually have to go way back in time. What explains erosion and the fact that the situation is critical in the fluvial section is that most of the shorelines consist of the same type of surface deposit, a slightly more loamy clay that reacts strongly to wake phases, causing alternating humidity and dryness, as a result of which it falls apart in sheets. In scientific terms, this is called the desiccation of clay soils. Nearly all the shorelines in the fluvial section are formed from this type of deposit.
Land use planning can have consequences. Sometimes these zones consist mainly of cohesionless material, a much more vulnerable deposit.
These two types of deposits are found in the fluvial section covering the zone where ship and boat wake occurs, between Lake Saint Pierre and Montreal.