Adrián Pedrozo-Acuña

Hurricane-induced waves and storm surge modeling for the Mexican coast

This paper describes the application of a third-generation wave model and a hydrodynamic model to determine extreme waves and water levels associated to the incidence of tropical cyclones along the Mexican coast. In addition to historical records and to overcome the limitation associated to data scarcity in Mexico, we employ information from 3100 synthetic events generated from a statistical/deterministic hurricane model. This enables the generation of a more robust database for the characterization of extreme water levels along the Mexican coast. The procedure incorporates a storm track modeling approach where, for each hurricane (historic and synthetic), the entire track is numerically reproduced as it crosses the ocean and makes landfall. Extreme values for both, waves and storm surge, are determined through an extreme value analysis at each mesh element, allowing for the identification of their spatial variability. Results for the Gulf of Mexico show that highest waves are expected along both the Caribbean Sea and the northern coast of the Gulf of Mexico, while extreme water levels due to storm surge are identified in the northern part of the Yucatan Peninsula. On the other hand, along the Pacific coast, extreme values for waves are identified at the central mainland Mexico while storm surge is minimal. The methodology is proved to be a good alternative in the reproduction of continuously varying tropical cyclone climatology along the Mexican coastline, and it provides a rational approach for assessing the hurricane-induced risk in coastal areas.

Failure of a drainage tunnel caused by an entrapped air pocket

A severe storm event occurred over the western area of Mexico City causing the rupture of a drainage tunnel, resulting in surface flooding, severe infrastructure damage and three deaths. This paper describes the methodology followed in order to validate the diagnostic of the event. The detailed investigation comprised in situ observation of the system, as well as hydraulic and structural analyses. In this case, severe pressure oscillations inside the tunnel caused by rapid filling and sudden air leakage through a large orifice (manhole) were recognized as the direct cause of the conduit burst. Further, the low strength of the concrete pipes of the tunnel, constructed without reinforced steel, and the low confinement by the dead load due to the soil above the tunnel also contributed to the rupture. The numerical results show a very unfavorable stress distribution along the tunnel stretch where the accident occurred, sufficient to cause the rupture.

Post-nourishment beach scarp morphodynamics

ABSTRACT Ruiz de Alegria-Arzaburu, A., Mariño-Tapia, I., Silva, R., Pedrozo-Acuña A., 2013. Post-nourishment beach scarp morphodynamics Large and persistent beach scarps can be safety hazards to beach users and result in serious social and economic implications. In this study the morphological evolution of beach scarps of large dimensions is examined on a nourished microtidal Caribbean Mexican beach. Beach profiles were measured three-to-four monthly along the beach after the nourishment in December 2009 and over 1.5 years. A beach scarp was defined as a feature with a slope larger than the critical angle of repose of 32° and a minimum height of 0.25 m. The top and bottom positions of the scarps were calculated from the minimum and maximum values of the second derivative of the measured beach profiles (slope gradient). The cross-shore morphological evolution of the scarps was related to wave runup (R2) and tides, and also to both with the contribution of the longshore energy flux (Pl). During calm conditions characterised by longshore uniform mean and maximum R2 of 0.73 and 0.83 m, and Pl=180KN/s, the scarps remained present along the beach. Energetic conditions with mean and maximum R2 of 0.83 and 1.2 m and Pl=400KN/s, increased the longshore rythmicity of the beach and induced significant cross-shore erosion (over 20 m) and the disappearance of ~50% of the scarps. The added contribution of the longshore energy flux, wave runup and tidal elevation explain 40% of the morphological evolution of beach scarps over the study period.

On the Role of Climate Change on Wind Waves Generated by Tropical Cyclones in the Gulf of Mexico

To generate projections of wave climate associated to tropical cyclones is a challenge due to their short historical record of events, their low occurrence, and the poor wind field resolution in General Circulation Models. Hence, synthetic tropical cyclones provide an alternative to overcome such limitations, improving robust statistics under both present and future climates. We use synthetic events to characterize present and future wave climate associated with tropical cyclones in the Gulf of Mexico. The NCEP/NCAR atmospheric reanalysis and the Coupled Model Intercomparison Project Phase 5 models NOAA/GFDL CM3 and UK Met Office HADGEM2-ES, were used to derive present and future wave climate under RCPs 4.5 and 8.5 scenarios. The GFDL model shows less bias in the present climate with respect to NCEP/NCAR results. Furthermore, the numerical results suggest an increase in wave activity for the future climate in the Caribbean Sea and Northern Gulf of Mexico, whereas some areas are expected to decrease the wave energy, as the stretch of the Gulf of Mexico between Yucatan and Southern Texas. The results have practical implications on the design of offshore structures. The 100-year design wave based on the present climate might result in under/over design of structures, owing to the lifespan of a structure that is within the future wave climate period.

Storm surge at a western Gulf of Mexico site: variations on Tropical Storm Arlene

ABSTRACT Storm surge was calculated based on 23 different scenarios of a tropical cyclone (TC) trajectory, intensity and translation speed making landfall over a radius of 100 km of the Pánuco River at Tampico, Mexico. At the coast, the highest water levels resulted when the landfall was directly over the study area. When the landfall was 50 km south the high water levels remained for the longest time and highest levels occurred upstream. Also, high water levels were sustained longer when the TC had a slow translational speed (∼2 m/s) relative to fast-moving storms (∼4 m/s). Negative water levels resulted for events making landfall north of the study area, which may increase flushing of the river discharge and mitigate flooding from river overflown. The implications of the different scenarios are discussed in relation to management and implementation of contingency plans.

HYDRORECESSION: A Matlab toolbox for streamflow recession analysis

Abstract Streamflow recession analysis from observed hydrographs allows to extract information about the storage-discharge relationship of a catchment and some of their groundwater hydraulic properties. The HYDRORECESSION toolbox, presented in this paper, is a graphical user interface for Matlab and it was developed to analyse streamflow recession curves with the support of different tools. The software extracts hydrograph recessions segments with three different methods (Vogel, Brutsaert and Aksoy) that are later analysed with four of the most common models to simulate recession curves (Maillet, Boussinesq, Coutagne and Wittenberg) and it includes four parameter-fitting techniques (linear regression, lower envelope, data binning and mean squared error). HYDRORECESSION offers tools to parameterize linear and nonlinear storage-outflow relationships and it is useful for regionalization purposes, catchment classification, baseflow separation, hydrological modeling and low flows prediction. HYDRORECESSION is freely available for non-commercial and academic purposes and is available at Matlab File Exchange ( http://www.mathworks.com/matlabcentral/fileexchange/51332-hydroecession ).

Experimental study on sediment advection and beach response under plunging wave breaking

ABSTRACT Pedrozo-Acuña, A., Resendiz, D., Gutiérrez, C., 2013. Experimental study on sediment advection and beach response under plunging wave breaking. This paper presents an experimental investigation into the morphological response of beaches under the action of plunging wave breaking. Experimental results performed under the same wave conditions, allowed the association of beach evolution to its porosity. Firstly a beach profile which presented the generation of a clear berm at the top of the profile and a beach step below the SWL (higher porosity) was illustrated. Secondly, an erosive condition of beach profile was characterised (lower porosity). The morphological responses of both beaches were differentiated in terms of the porosity of the beach, which highlight its role in the resulting spatio-temporal nature of the momentum balance under plunging wave breaking. Additionally, BIV derived velocities were utilised as a tool for the investigation of hydraulic regimes responsible of generating different beach responses and sediment sorting in the laboratory. Through Eulers equation the total acceleration was deconstructed, allowing a careful assessment of the contribution of each the acceleration terms to the resulting momentum balance. Notably, the contribution of the local acceleration term is insignificant all along the beach profile, while the role of advective terms cannot be overlooked.

Evaluación de la marea de tormenta en sitios con escasez de datos: río Pánuco, México

Abstract Storm surge from tropical cyclones is the main cause of flood induced damage in tropical regions. Nevertheless, storm surge estimations are limited by the scarcity of measurements and historical information of tropical cyclones. This is particularly true in Mexico because data is very scarce. Thus, this research presents an alternative method for estimating storm surge values from tropical cyclones for different return periods, in areas with insufficient historical information. The selected framework consists on the implementation of hydrodynamic models to reproduce the mean sea level elevation induced by the presence of tropical cyclones on the coast. For this, we used synthetic events (120 events) generated in the Atlantic Ocean during the defined time period between 1980.2010 and limited to a 100km circular region around the mouth of the Panuco River in Mexico (22.26.N, 97.78.W), together with historical events (25) occurring between 1951 and 2012. The wind fields of these events are used as forcing for a hydrodynamic model in order to define the maximum storm surge at the point of interest. The obtained information allows for a more reliable extreme value analysis to determine storm surge levels for different return periods. The results demonstrate the usefulness of this methodology for using synthetic events in combination with historical information, in order to increase the reliability of the design values in areas with limited data.

77. ON THE ROLE OF IMPULSIVE PRESSURES INDUCED BY PLUNGING BREAKERS ACTING ON GRAVEL BEACHES

This paper presents a discussion on the role of impulsive pressures induced by plunging breakers acting on gravel beaches. In previous works, this process has been hypothesized to play a major role in the observed sediment transport on these beaches. Thus, a diagnostic investigation is carried out here in order to elucidate, in more detail, the anatomy of the impulsive signature in the pressure signal. For this purpose, we employ an integrated approach, which comprises full scale laboratory measurements and their comparison against model results from a well-validated phase/depth resolving numerical model based on the Reynolds-Averaged Navier-Stokes (RANS) equations. Agreement between observations and model predictions allows us to investigate the contribution of each of the acceleration terms in the momentum balance under the wave-impact event by means of the numerical model. The discussion is presented in order to understand how impulsive pressures are generated under plunging waves and their role in sediment mobilisation. Consistent with prior studies, numerical results show that under plunging breakers the local acceleration (du/dt) alone cannot be used as a proxy for pressure gradients. In addition, the importance of the term w du/dz of total acceleration is recognised for first time. Results from this study suggest that for different types of breaking a different characterisation of the pressure gradient may be sought.