Thomas,
Over the years, I have seen "armoring" banks come close to standard in the US. Then, with the environmental movement, the trend is to naturally vegetate the banks as chemical input filters. With some of the good erosion mats available to protect the slopes, and maybe a little hand watering to speed up germination, it can be done.
Erosion is definitely a factor. Just as irrigation designers usually give output that is rarely used after germination, sometimes, the drainage plan is developed to limit flow just during grow in, a la catch basins ever 200-max 300 feet. My current project was an old course with lots of erosion.
Causes included slope, loose sandy soil, poor irrigation coverage, and low budgets leading to low mower maintenance, i.e., poor cutting blades. Every time one made a nick, turf was gone, erosion started. Another interesting situation there, which I have seen a few times (most famous in US is Kansas City Plaza area) where both storm path and creek run the same direction, resulting in substantially more flow along the stream for the same rain than where the storms cross a watershed at 90 deg.
Short version, erosion considerations can be big whup in design.