What is weathering and erosion? Migration of sand dunes across irrigated fields and construction of housing developments is a big problem in parts of the world. Write about your ideas on how such sand encroachment might be stopped. Remember the ways in which sand-sized grains are transported and deposited. Hint: Homework reading assisgnment. Sand encroachment is said to take place when grains of sand are carried by winds and collect on the coast, along water courses and on cultivated or uncultivated land.