Investigation on the longshore transport mechanism along San Fernando Bay, La Union

With the Philippines being an archipelago, accelerated sea level rise can pose a threat to the coastlines of the country. Negative effects brought by the rise of sea levels can be flooding, erosion and salt water intrusion. The effects brought by the increase in strength and reoccurrence of storms would lead to coastal erosion. Different studies regarding sandy beaches have estimated that around 70% of the coastlines around the world recedes. One of the areas highly affected by coastal erosion is San Fernando Bay, La Union. Studies brought by Remotigue and Zamora (2004) and Bayani-Arias & Dorado (2012) have shown that a huge part of La Union is highly susceptible to erosion. With the group\u27s focus on longshore sediment transport, the paper aims to investigate the effects of different coastal parameters such as wind, wave, tide and current on the longshore rate of the study area chosen. Different parameters were then derived such as grain size, peak wave period, wave breaking height, wave breaking angle and transect orientation that would help in solving for the empirical formulas. The derived parameters were then used in the two most widely used formula, Kamphuis and CERC, and helped the group determine the equivalent longshore transport rate using the secondary data gathered from NAMRIA and PAG-ASA in the years of 1960, 1980, 2000 and 2016. It was then determined that the highest longshore transport rate value occurred during the year 1980. To supplement the findings of the researchers using the empirical formulas, a numerical based model known as DELFT3D was used to see the total longshore transport in the area. Carefully analyzing both empirical and numerical outputs, it was determined that the Kamphuis formula yielded closer results to DELFT3D since it was within the range of the values presented by DELFT3D. In conclusion, with the very high value obtained from the longshore transport rate in 1980 and the significant difference in the year 1960, it can be said that there is a spatial imbalance between these years due to the increase in the different parameters that governs the area such as wind, wave and tide which contributed to the rapid erosion rate area. As for the years 2000 and 2016, the longshore transport rate is slightly close to one another that if compared to the existing shoreline map, it reflects that there is no significant changes during the 16 year interval