Accretion is the accumulation of sand or land mass over time along coastal regions. This occurs through a combination of ocean currents and the movement of oceanic and continental plates, or through human activity.
Naturally, sand builds up in areas from the movement of water currents and tectonic plates, forming mounds. Accretion has benefited humans in extending land out from shorelines and being able to make more land for human activity and living. This has also posed a problem; over accretion can harm marine life in those areas which are not used to sudden changes in the environment.
Pidwirny, M. (2006). "Glossary of Terms: A". Fundamentals of Physical Geography, 2nd Edition. http://www.physicalgeography.net/physgeoglos/a.html. Accessed July 11, 2016.