Perhaps the experts referred to, might investigate the history of this corner before wasting more money trying to stabilise the artificial river bank in question. Nature and the flow characteristics of this river bend, originally provided a mostly stable river bank, before poor engineering from around the 1950/60’s, saw a cut and fill design implemented to widen the corner, rather than more property acquisition and a total cut design. So forget wasting money on something that will never be achieved, purchase the necessary property to achieve the road widening, and let the river bank return to what nature intended.