Jorge O. Pierini

Fractal analysis of tidal channels in the Bahı́a Blanca Estuary (Argentina)

The fractal dimension (D) was estimated for nine tidal channels depicted in thematic mapper (TM) Landsat-5 imagery to derive information about the degree of geomorphological control on a tidal channel network characteristic of the Bahia Blanca Estuary (Argentina). Two methods, box counting and contiguity, were used to estimate fractal dimensions for each tidal channel. All channels produced D values close to 1, meaning that they are self-affine fractal features. However, these fractal dimensions do not represent the meandering pattern complexity characteristic of the tidal channels analysed. Although both methods allowed for estimation of D, the contiguity method showed that three of the channels actually are not fractal but have sinusoidal characteristics, a condition that was not detected by the former method.

Residual Flow Structure at a Scour-hole in Bahia Blanca Estuary, Argentina

Abstract Two-dimensional data of mean and sediment flow collected at a natural confluence of channels in the inner Bahía Blanca Estuary are presented. We describe the two-dimensional flow field to assess the role of changes in bed morphology occurring during transport-effective events on the structure of flow at a confluence; and to examine how the flow structure varies with changes in the ratio of momentum flux. At each station, vertical profiles of velocity, salinity, temperature and suspended sediment were obtained during the whole tidal cycle and residual fluxes were obtained. Lagrangean flux is higher than possible fresh water input, denoting an extra output of water which is the flux over the tidal flats along the southern and northern coasts of the channel. The effect of the junction produces a distortion of the vertical profile flow and in the suspended sediment transport. The effect of the particular conformation of the system makes necessary for consider the lateral effect of the tidal flats in the circulation of the estuary which exerts a significant influence.

Factors Influencing the Distribution and Characteristics of Surface Sediment in the Bay of Cartagena, Colombia

ABSTRACT Restrepo, J.C.; Escobar, J.; Otero, L.; Franco, D.; Pierini, J., and Correa, I., 2017. Factors influencing the distribution and characteristics of surface sediment in the Bay of Cartagena, Colombia. This study evaluated patterns of coastal sediment movement and deposition under different seasonal conditions (warm and cold phases of the El Niño–Southern Oscillation [ENSO] and normal conditions) in Cartagena Bay, Colombia. A calibrated numerical model (MOHID modeling system) was applied to assess the spatial distribution of sediments transported by the Canal del Dique to the bay and studied the spatial distribution and major textural characteristics of 234 surface sediment samples. Currents in the Bay of Cartagena are controlled primarily by the strength and direction of the wind. Model results show major sediment deposition in the southern sector of the bay during the dry season. More homogenous spatial distribution of sediments throughout the Bay of Cartagena occurs with an increase in river inputs from the Canal del Dique. These patterns were enhanced or weakened, respectively, by cold and warm phases of the ENSO. Predominant sediments were medium size (ϕ = 5.35 ± 1.2), poorly sorted (σ = 1.63 ± 0.8), with notable asymmetry (Sk = −0.052 ± 0.2) and kurtosis (k = 0.84 ± 0.4). Sediments with lower sand content (<5%) are located along a latitudinal axis from the Canal del Dique delta to the western end of the island of Tierrabomba. CaCO3 content of the sediments is <10%. Water and sediment flow, controlled by the Canal del Dique, has favored the transport and deposition of poorly sorted, symmetric, and mesokurtic mud in most of the Bay of Cartagena. As a result, autogenous calcareous sediments have been covered by fine terrigenous sediments that were delivered via the Canal del Dique. Thus, the channel plays a more prominent role in sediment transport and deposition in the Bay of Cartagena than thought previously.

Discriminating between different streamflow regimes by using the Fisher-Shannon method: An application to the Colombia rivers

The Fisher-Shannon (FS) information plane, defined by the Fisher information measure (FIM) and the Shannon entropy power (NX), was robustly used to investigate the complex dynamics of eight monthly streamflow time series in Colombia. In the FS plane the streamflow series seem to aggregate into two different clusters corresponding to two different climatological regimes in Colombia. Our findings suggest the use of the statistical quantity defined by the FS information plane as a tool to discriminate among different hydrological regimes.

Changes in seasonal streamflow extremes experienced in rivers of Northwestern South America (Colombia)

A measure of the variability in seasonal extreme streamflow was estimated for the Colombian Caribbean coast, using monthly time series of freshwater discharge from ten watersheds. The aim was to detect modifications in the streamflow monthly distribution, seasonal trends, variance and extreme monthly values. A 20-year length time moving window, with 1-year successive shiftments, was applied to the monthly series to analyze the seasonal variability of streamflow. The seasonal-windowed data were statistically fitted through the Gamma distribution function. Scale and shape parameters were computed using the Maximum Likelihood Estimation (MLE) and the bootstrap method for 1000 resample. A trend analysis was performed for each windowed-serie, allowing to detect the window of maximum absolute values for trends. Significant temporal shifts in seasonal streamflow distribution and quantiles (QT), were obtained for different frequencies. Wet and dry extremes periods increased significantly in the last decades. Such increase did not occur simultaneously through the region. Some locations exhibited continuous increases only at minimum QT.

Numerical simulation of a stable planetary boundary layer over the Argentine continental shelf

A two-dimensional planetary boundary-layer model is employed to simulate numerically observed temperature and humidity profiles of an airflow over the Argentine continental shelf. Predicted profiles satisfactorily agree with observed ones which are characterized by a stable boundary layer.

Saltwater Intrusion into a River with High Fluvial Discharge: A Microtidal Estuary of the Magdalena River, Colombia

ABSTRACT Ospino, S.; Restrepo, J.C.; Otero, L.; Pierini, J., and Alvarez-Silva, O., 2018. Saltwater intrusion into a river with high fluvial discharge: A microtidal estuary of the Magdalena River, Colombia. The Magdalena River (Bocas de Ceniza) forms a microtidal estuary subjected to numerous interventions aimed to guarantee navigability towards the port of Barranquilla, Colombia. Significant sedimentation processes are still frequent in this area, however. Understanding the dynamics of both saltwater intrusion and mixing conditions is a fundamental requisite to understanding the sedimentation dynamics in these types of estuaries. The effects of river discharge, tide, and winds on stratification patterns, and mixing and saltwater intrusion dynamics in the estuary of the Magdalena River were evaluated, focusing on the effects of river discharge variability. The three-dimensional hydrodynamic model MOHID was implemented, and calibration and validation of the model were carried out using in situ velocity, temperature, and salinity data, obtaining Skill values greater than 0.90. To cover a wide range of variability in the main forcing factors (fluvial discharge, tide, and wind), the conditions recorded in 2010 were simulated when both phases of the El Niño–Southern Oscillation phenomenon occurred. During that year, the river discharge ranged between 2465 and 16,463 m3 s−1. Results revealed a stratified, saltwater wedge estuary, the dynamics of which were mainly dominated by river discharge. Tide and winds altered saltwater intrusion dynamics, mainly during low-discharge periods.

Suspended Sediment Fluxes in the Middle Reach of the Bahia Blanca Estuary, Argentina

Puerto Galvan (Fig. 1) is one of the five harbors that form the BahIa Blanca Harbor System, the largest and deepest of Argentina. The harbors are all located along the Canal Principal of the BahIa Blanca Estuary, a mesotidal, coastal plain environment (Perillo, 1995) formed by a series of major NW-SE trending channels separating extensive tidal flats, low salt marshes and islands. The geomorphology and physical characteristics of the estuary are described in detail elsewhere (Perillo and Piccolo, 1999) including a recent review of its major environmental features (Perillo et al., 2000).