Answer:
The groin should be built perpendicular to the shore, and to the west of your house.
Explanation:
The groin will prevent beach erosion over time. And will help to stabilize the beach, if built correctly.
The winds will speed up the longshore drift process, and that is why the groin must be built to the west, to trap the sand and sediments before its washed away.
A beach groin is expected to last for about 40 to 50 years, so the problem would be solved for at least your entire generation.