What is your local water supply like?
Seasonal rivers with high sand loads are idea for making sand dams. The idea is you construct a dam down to the bedrock, and across the whole channel. The water builds up behind, losing velocity. Where it loses velocity it drops the load of sand. Over a period of time (one big storm, or a few years) the depth of sand builds up to the top of the dam.
Beneath the surface of the sand is where the magic happens. A deep bed of sand has a huge pore space, which fills with water. The sand protects the water from evaporation and acts as a reservoir year round. Traditional water harvesting techniques can be used to get the clean drinking water from the sand - including hand dug wells. These sand dams give long-term water security and can form the basis of irrigated crop planting, rehydration of the surrounding landscape, and general greening of the environment. Plants thrive along rivers that have these, because the water slowly spreads sideways to where the roots can access them.
There are many videos of them online, and there are organisations that help communities construct them. They take considerable labour, but can be build just with hand tools as you describe.
Otherwise, looking at vetiver hedges is my top recommendation. Vetiver hedges planted on contour parallel to the banks will prevent soil erosion. They are a valuable mulch source and help build soil organic matter and increase soil fertility in the longer term. In arid climates, where flash rains storms carry surface sediment, they can build up natural terraces for cultivation - all while conserving soil and nutrients. Protecting the banks from further erosion will certainly help, but I'm not sure what you can do to help with the sediment being washed in from further up stream, beyond potentially slow it a bit and try to trap some. My feeling is that in the middle of a strong stream flow even vetiver will likely be eroded away, but bank protection will probably work.