The back of the shoreline is defined by the MDMAP as the first major change in substrate, which may include a vegetation line, cliff, or other barrier. If you are interested in also monitoring debris that may be pushed back into vegetation behind the beach during storms, that debris should be tallied on a separate data sheet so that it's not included in the calculated debris flux or concentration.
Beach slope is a measure of the angle of the beach, which affects how debris is deposited on the shoreline. Although rigorous approaches to measuring beach slope exist, for the purposes of MDMAP, beach slope can be visually estimated. For your shoreline characterization, please record the slope of the beach in the foreshore or the beach face (the area between low and high tide). The beach slope may steepen or flatten seasonally and over time (e.g., large storm events may increase the slope).
Tidal distance is the horizontal dimension of the beach, measured perpendicular to the shoreline, from the average low tide line to the average high tide line. Arrive at your site at low tide and measure the distance from the water’s edge to the high tide wrack line.
When you conduct your initial shoreline characterization, it is important to arrive at the site at low tide so that you can capture the entire width of the beach. In order to record GPS readings at the water’s edge, watch the breaking waves to try to determine the shoreward extent of the water. Record coordinates at that point. If a portion of the shoreline site is underwater at subsequent surveys do not try to enter the water to survey.