Volume of sediment above a certain height - help

I currently have an aerial photograph of a barrier beach, and corresponding lidar data for the 2005 photo, 2007 photo, and 2013 photo. I want to calculate the volume of sediment on the beach for each year above sea level. There are various guides but i am still confused how to do this for just the area of beach i have no the whole area of lidar. The lidar files are tiff.

Using arcmap 10.2.2