Groin fields refer to a series of structures set up perpendicular to the shore line that are used to prevent beach erosion. Groins are most effective when the water flows in a manner that makes the sand move parallel to the shore line. Modern groins are built of reinforced concrete which allows them to serve their purpose without degradation.
The affect of groin fields is an accumulation of sand on the updrift side and depletion on the downdrift side. The shoreline takes on a saw tooth shape due to this. Enriched sediments can be placed between groins to allow a healthy growth of plants and encourage the growth of diverse biological life at the edge of the beach.
The only problem with the use of groin fields is that they lead to regions on the downdrift sides losing sediment which accelerates erosion there. A sediment prefill is required to prevent this.