A river bank protection was an urgent need after a river overflowed its banks twice in a short amount of time. The job needed to be: done fast, be strong, be cost-effective.
The choice was to use gabion retaining walls as they are heavy and therefore able to resist the river during a flood. Material and labour costs are a huge influence in the final price of the containment wall however price can be reduced by filling the gabions with locally sourced stones.
The only requirement is that the stones should be roughly the same size.
They can be outsourced in nearby quarries, but obviously purchasing the stones and transport costs are a great influence in the overall protection system cost, especially when the location of the job is not easy to access.