Even the orientation of furrows helps. Not having them perpendicular to the river the furrows should be parallel.
Even provincial workers cutting trees need to use canola oil for bar oil (bar and the saw chain lubrication).
Farms can have runoff of fertilizer and it can cause fish to die rapidly in large groups aka a "fishkill". The farmer is fined too.
I think this has more to do with flood plain management. Some countries prohibit construction within X meters of the average water level because that's expectedly where water will rise. In some shallow areas municipalities even build parks with no permanent structure because of the high probability those areas will be flooded, and that ensures no life is put at risk and economic damage is limited to whatever infrastructure was placed there (i.e., park benches, public restroom, small public cafe, camping ground, etc.)