Browsing by Author "Villagrán, Mauricio "

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    Coastal Evolution in a Wetland Affected by Large Tsunamigenic Earthquakes in South-Central Chile: Criteria for Integrated Coastal Management
    (MDPI, 2021) Martínez Reyes, Carolina Del Pilar; Sepúlveda-Zuñiga, Einer; Villagrán, Mauricio; Rojas, Octavio; Gómez, Matias; López, Pablo; Rojas Quezada, Carolina Alejandra; CEDEUS (Chile)
    The coastal evolution of the microtidal Tubul-Raqui wetland in south-central Chile (36 degrees S), which historically has been affected by large earthquakes and tsunamis, particularly the 1960 (Mw = 9.5) and 2010 (Mw = 8.8) subduction earthquakes and their associated tsunamis, is analyzed. Historical aerial photographs and topographic and bathymetric surveys from the 1961-2017 period, as well as salinity, sediment, and flora data obtained following the 2010 earthquake were used for comparison with data from prior to the event. A steady state of the shoreline was established, with an average erosion rate of -0.016 m/year in the 1961-2017 period. However, erosion predominated in the period between these two large earthquakes (1961-2009), with an average rate of -0.386 m/year. The wetland dried up, partially recovered saline intrusion a year later, and recovered the salinity conditions it had before the earthquake two years later. The postearthquake effects on the floristic composition were not significant, with the species Spartina densiflora, which presented a high tolerance to these types of changes, predominating. Moreover, 75 percent of the taxa in pre- and postearthquake conditions coincided, with the halophyte species Spartina densiflora, Sarcocornia fructicosa, and Cotula coronopifolia predominating, while the best-conserved community was Spartina-Sarcocornia association located in the saltmarsh. Seven years after the earthquake, the shoreline presented an accretion rate of 2.935 m/year; if the current tectonic conditions prevail, an erosive trend can be expected in the coming decades. The morphological variability and the changes associated with the shoreline in this wetland are strongly controlled by tectonic factors. Criteria aimed at integrated coastal management to promote its occupancy and use in accordance with its evolutionary dynamics are proposed.
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    SWASH ZONE BASED REFLECTION DURING ENERGETIC WAVE CONDITIONS AT A DISSIPATIVE BEACH: TOWARD A WAVE-BY-WAVE APPROACH
    (2014) Almar, Rafael ; Catalán, Patricio ; Ibaceta, Raimundo; Blenkinsopp, Christopher; Cienfuegos Carrasco, Rodrigo Alberto; Villagrán, Mauricio ; Aguilera, Juan Carlos; Castelle, Bruno
    This paper presents a 11-day experiment conducted at the high-energy dissipative beach of Mataquito, Maule Region, Chile. During the experiment, offshore significant wave height ranged 1-4 m, with persistent long period up to 18 s and oblique incidence. Wave energy reflection value ranged from 1 to 4 %, and results show that it is highly linked to both incoming wave characteristics and swash zone beach slope, and is well correlated to a swash-slope based Iribarren number. The swash acting as a low-pass filter in the reflection mechanism, our results show that thecut-off period is better determined by swash slope rather than incoming wave's period. A new low cost technique for observing high-frequency swash hydro-morphodynamics is introduced and validated using LIDAR measurements. A good agreement is found. Separation of uprush and backswash components using the Radon Transform illustrates the low-frequency filtering effect. These results show the key role played by swash mechanism in the reflection rate andfrequency selection. More investigation is needed to describe the reflection process and its link with shoreface evolution, moving toward a swash-by -swash approach.