18. Every person constructing or improving a road that crosses a watercourse shall preserve the ground cover and the stumps within 20 m of the watercourse, outside the roadway, the shoulders and the slopes of the road’s embankment, as measured from the natural high-water mark.
At that same time, the slope of the road’s embankment, between the banks of the watercourse and under the depth of flow for which the embankment was designed, shall be stabilized with a geotextile membrane covered with riprap or a retaining wall.
The slope of the road’s embankment not covered by the second paragraph shall be reduced to a ratio of at least 1.5(H): 1(V), and that embankment shall be stabilized using the usual techniques, such as those referred to in section 25, within 20 m from the watercourse referred to in the first paragraph and above the watercourse if the road structure includes an embankment.
The third paragraph of this section does not apply to anyone who stabilizes the embankment referred to in that paragraph with a geotextile membrane and riprap.