I have a small stream about 3ft wide, that dries up in mid summer, but
can be a raging torrent in winter up to 2ft deep.

The bank sides are approx 40 deg sloping, and made of builders rubble
and soil.

The stream bed looks like it just builders rubble.

Over the years the banks have started to be undercut with the water,
and then the bank gives way. So the stream is getting wider and the
banks are getting steeper.

Access is very limited and there is no chance of getting any machinery
in, except hand tools.

Any ideas on the best way, and cheapest of trying to stop this
errosion.