Secondary lahar hazard assessment for Villa la Angostura, Argentina, using Two-Phase-Titan modelling code during 2011 Cordón Caulle eruption

This paper shows the results of secondary lahar modelling in Villa La Angostura town (Neuquén-Argentina) based on the Two-Phase-Titan modelling computer code, which aimed to provide decision makers a useful tool to assess lahar hazard during the 2011 Puyehue-Cordón Caulle Volcanic Complex eruption. Possible occurrence of secondary lahars that could reach the city was analized. The performance of the Two-Phase-Titan model using 15 m resolution DEMs developed from optical satellite images and from radar satellite images was evaluated. The output of these modellings showed inconsis- tencies that, based on field observations, were attributed to bad adjustment of DEMs to real topography. Further testing of results using more accurate radar based 10 m DEM, proved more realistic predictions. The procedure allowed to simulate the path of flows from Florencia, Las Piedritas and Colorado creeks, which are the most influenc- ing streams in Villa La Angostura. The output of the modelling is a valuable tool for city planning and risk management especially considering the glacial geomorphology features of the region, the strong urban development growth and the land occupation tendencies observed in last decade in Villa La Angostura and its surroundings

Surface heat exchanges in an estuarine tidal flat (Bahía Blanca estuary, Argentina)

The purpose of this article is to provide an analysis of the heat exchanges occurring at a tidal flat of the Bahía Blanca estuary (Argentina). Heat fluxes across the water-atmosphere and sediment-atmosphere interfaces (inundation and exposure, respectively) were studied. Data were collected at Puerto Cuatreros (located near the estuary's head) during one annual cycle (2003). Bulk aerodynamic formulas were used to estimate the radiative and turbulent fluxes from available meteorological data. Air, water and soil temperatures, as well as solar radiation were measured every 10 min. Soil temperature was recorded at three depths (0.05, 0.15 and 0.25 m). Meteorological data were obtained at 30-min intervals from the estuary's weather station located at Puerto Rosales. Atmospheric and tidal conditions regulated the heat exchanges. The most important heat fluxes in every season were net radiation and latent heat flux, reaching maximum values of 816 and 776 W m–2, respectively, after midday in summer. Tidal inundation affected the direction and magnitude of sensible and soil heat fluxes. During a cloudless summer day, nocturnal inundations heated the tidal flat sediment, causing an upward flow of sensible heat. A tidal inundation in the morning cooled the sediment and a downward flow of sensible heat developed (reaching –183 W m–2). Soil heat flux was rapidly reduced during the hours of inundation, becoming nearly zero. The estimated annual evaporation was 2127 mm.

Soil heat exchange in Puerto Cuatreros tidal flats, Argentina

 Some interaction processes at the sediment-water and sediment-atmosphere interfaces were analyzed for each season of the year using mass aerodynamic formulas. Data were collected from Puerto Cuatreros tidal flats (Bahía Blanca estuary, Argentina) during an entire year (2000). The soil temperature was measured every 10 min by a thermistor chain at three levels below the sediment surface (–0.05, –0.15 and –0.25 m). Water and air temperatures, solar radiation and meteorological data were registered simultaneously, resulting in annual means of 14.07ºC (soil at –0.15 m), 13.69ºC (air) and 14.51ºC (water). Atmospheric and tidal conditions regulated the mudflat's thermal behavior. The soil temperature vertical profiles showed a diurnal and semidiurnal cycle due to the influence of these factors. The diurnal thermal amplitude at –0.05 m reached 14.6ºC on 20 February 2000, but only 2.8ºC on 1 July 2000. Most fluctuations of sediment temperatures were observed in the first 15 cm, with vertical gradients of 0.82ºC cm–1 during summer. In order to obtain the soil heat capacity, the granulometric composition of a sediment column was analyzed. Soil heat fluxes during a typical summer and winter day were compared. A net heat gain in the soil was observed during the summer day (+840.6 kJ m–2) and an inverse situation was found in winter, with a diurnal heat exchange of –768.6 kJ m–2