Geomorphologic changes on beaches as a result of strong winds. The case of the Pehuen Co beach, Argentina

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 m(3)) 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.