Measurement of Swash Infiltration Rates on Sandy Beaches

Abstract

The swash zone is a critical area of the nearshore hydrodynamics contributing significantly to beach evolution. The role of infiltration of water during swash events has been investigated, but an enhanced data collection methodology will improve prediction and analyses of swash processes. A new and simple technique was proposed to determine the rate of swash infiltration on sandy beaches. Direct, in situ measurements of swash infiltration rates were conducted on the sandy beach of Las Cuevas Bay located on the north coast of Trinidad. The method incorporated the use of a double ring infiltrometer paired with a Bluetooth water level logger, where infiltration rates were inferred from the changes in water level recorded within the double ring infiltrometer. Observed infiltration rates were variable and showed a dependency on sediment characteristics and location of measurement. The study also sought to ascertain any correlation between the measured infiltration rates and sediment properties. While correlation was generally low, the use of the maximum recorded infiltration rate yielded the best correlation across most cases observed. In addition, the highest correlation occurred with the D10 grain size for the upper beach, and the D90 grain size for the lower beach which is closer to the Still Water Line. The sediment sorting ratio of D84/D16 and D90/D10 showed the best correlation for the upper and lower beach locations respectively. While the field method was practical, the results of the study demonstrate a need to capture additional bed features that contribute to the rate of infiltration.