Efectos geomorfológicos de fuertes vientos sobre playas. El caso de la playa de Pehuen Co, Argentina

Abstract

El objetivo de esta investigación fue analizar el efecto de los vientos fuertes sobre la erosión y cambios geomorfológicos de la playa de la Villa balnearia Pehuen Co (Buenos Aires, Argentina). Se estudiaron cuatro sectores de costa del balneario de diferentes características y orientaciones. Se analizaron datos de viento de una estación meteorológica localizada en la costa y se midieron mensualmente perfiles de playa durante el período 2007-2009. También se estudió la granulometría del médano, espaldón, berma y línea de bajamar. Los resultados mostraron que dependiendo de la dirección del viento los efectos fueron diferentes en cada sector. La zona Oeste y Centro fueron las más perjudicadas ante eventos del cuadrante SW. En cambio las zonas Este y la Reserva fueron afectadas por erosión (13 m3) con los vientos del cuadrante SE. Con estos resultados se desarrolló un mapa de vulnerabilidad de la costa.The effect of strong winds on the erosion and geomorphological changes in Pehuen Co beach (Buenos Aires, Argentina) were analyzed. Although four different sectors of the coast with variable orientations were identified, in all cases the beach is dissipative with two or three parallel bars. The West Zone (ZW) is an extensive beach composed of medium to fine sand, backed by dunes covered with tamarisx gallica and a coastal road that artificially modified the dunes resulting in a cliffy backshore. The Center Zone (ZC), more urbanized, has beach less extense and dominated by fine sand; dunes covered with tamarisx gallica. The East Zone (ZE) has the widest beaches and medium sand; it coincides with the end of the urbanization. Finally the Reserve Zone (ZR), where there are trace fossils, is the most extensive and widest beach with fine sand and dunes naturally vegetated; it has no roads or infrastructure. Wind data from a meteorological station located on the coast and related to the monthly beach profiles during the period 2007-2009 were analyzed. The events offshore winds (SE and SW quadrants) were identified. It was determined that 40 km h-1 is threshold of wind speed and durations greater than 6 h are required to significantly affect coastal geomorphology. The results showed that different wind directions generate erosion and/or accretion in each sector. 91 events were recorded, most of the SW quadrant. The West and Central zones were the most vulnerable to events from SW quadrant. The East zones were eroded (13 m3) by the winds from the SE quadrant. Based on this analysis, a map of coastal vulnerability was developed showing that the western and central zones were the most vulnerable. The other two zones had a middle and lower vulnerability most likely due their natural stages not affected anthropogenic factors.