Shoreline Detection on a Gravel Beach using Argus remote sensing, Slapton Sands, Devon

This report presents the findings of an investigative study into the use of Argus video imaging techniques (Holman, 1994) for shoreline detection at Siapton Sands a steep gravel beach on the south Devon coast. Field observations of wave run-uplbackwash from the 10th_13th June 2006 are utilised as a comparative measure to the shoreline detection model embedded in the Argus software (Aarninkhof et al. 2003). Through the runup/ backwash observations the shoreline was determined to lie relatively low in the swash zone at 29.67% wave transgression in a wave backwash distribution. Argus derived shorelines for corresponding states of tide were found to lie consistently shoreward of the run-up/backwash derived shorelines by a mean horizontal offset of 2.49m. This suggests that two differing shoreline indicators are being detected. Regression analysis between the two data sets yielded R2 values of 0.9935 in the horizontal and 0.856 in the vertical suggesting that a level of discrepancy exists in the vertical. Comparisons between video and total station survey show reasonable agreement with R2 and standard error of 0.995 and 0.23m respectively. With an appreciation into the accuracy of the video imaging technique when applied to Siapton Sands an investigation in to the evolution of the shoreline over a winter/summer cycle was conducted. Considerable variation in shoreline position was observed with the largest shoreline migrations occurring at the north end of the beach. Sediment movement was deduced to be significant both in the cross-shore and longshore directions. Highly energetic wave climates were deduced to be responsible for a seaward migration of the shoreline and that in low energetic periods the beach returned to a state of equilibrium. In general, it is the believed that the Argus video technique works reasonably well for a steep reflective beach such as Siapton Sands.Faculty of Scienc