Gerardo A. Riccardi

Potential increase in coastal wetland vulnerability to sea-level rise suggested by considering hydrodynamic attenuation effects

The future of coastal wetlands and their ecological value depend on their capacity to adapt to the interacting effects of human impacts and sea-level rise. Even though extensive wetland loss due to submergence is a possible scenario, its magnitude is highly uncertain due to limited understanding of hydrodynamic and bio-geomorphic interactions over time. In particular, the effect of man-made drainage modifications on hydrodynamic attenuation and consequent wetland evolution is poorly understood. Predictions are further complicated by the presence of a number of vegetation types that change over time and also contribute to flow attenuation. Here, we show that flow attenuation affects wetland vegetation by modifying its wetting-drying regime and inundation depth, increasing its vulnerability to sea-level rise. Our simulations for an Australian subtropical wetland predict much faster wetland loss than commonly used models that do not consider flow attenuation.

Simulation of erosion-deposition processes at basin scale by a physically-based mathematical model.

Abstract The development and application of the physically-based and spatially-distributed mathematical model CTSS8-SED is presented. The model simulates hydrologic-hydraulic processes produced by storm events and related soil erosion and sediment transport processes at basin scale in lowland areas. The model simulates (i) storm runoff, (ii) soil detachment by raindrop impact and overland flow (gross sediment yield), (iii) sediment transport by overland flow and associated erosion-deposition processes and (iv) sediment transport by stream flow and riverbed erosion-deposition processes. A quasi two-dimensional representation of water flow and sediment transport routing is made by means of interconnected cells approach. The model is applied to simulate two flooding events in the Luduena Creek basin (Santa Fe, Argentina) occurred in April 1994 and March 2007 due to extraordinary rainfalls.

Grid size effects analysis and hydrological similarity of surface runoff in flatland basins

ABSTRACT The effects of grid-size modification on the derived topographic attributes are analysed and a procedure for scaling model parameters and similarity assessment between flow variables is proposed. Hydrological simulations are performed with a physically-based and spatially-distributed quasi-2D mathematical model. The scaled model parameters are the effective roughness coefficient associated with overland flow (nov) and the transverse slope in the cell (TSC). To scale the selected parameters, the criterion of equilibrium storage conservation between the different grid sizes is applied. Three basins of the central-east region of Argentina are modelled. The spatial variability of basin geomorphology is quantified using the entropy concept. The simulation results show that when grid size is increased, to obtain similar hydrological responses it is necessary to increase the nov or to reduce the TSC. In terms of similarity, the best results are achieved when TSC is scaled, particularly when water depths are considered.

A hydrological model to evaluate environmental impacts due to extensive irrigation. Case study: basin of the Ludueña Stream, Santa Fe, Argentina.

A mathematical model of hydrological simulation quasi-3D is described. The model is suitable to simulate the hydrological behaviour in flat land considering interactions between the surface zone, vadose zone (UZ) and saturated zone (SZ). The space domain is discretized in layers of surface and underground cells. In each cell, the model can quantify state variables dynamically (interception, surface storage, UZ and SZ storages) and exchange flows (evapotranspiration, infiltration, surface and groundwater flows, flow through constrictions). This aptitude of connecting surface and groundwater hydrology enables the model to predict changes in the hydrological process due to human activities at basin scale as well as long term impacts. In this paper results of the application and calibration of the model for the Luduena Stream System (Santa Fe, Argentina) are described. The model was run to evaluate the hydrological effects that arise out of four extensive irrigation scenarios in the Luduena Stream basin. The simulation is done for a period of twenty years. The considered scenarios are as follows: #0 corresponds to the present situation in the basin, for which the model was calibrated; #1, #2 and #3 are three hypothetical scenarios where the soil moisture levels are 60%, 75% and 90% of the field capacity, respectively. It is demonstrated that scenario #1 does not have great consequences for the hydrological process and does not contribute to groundwater vulnerability. The results for scenario #2 present important consequences for the hydrological process of the real system. An increment in the recharge of the aquifer is found, modifying the groundwater table, with higher impact in low areas. The vulnerability to the contamination processes rises considerably towards the basin head. For scenario #3, the hydrological process has a very significant variation, not only for the mean and extreme hydrological values but also for the space patterns. The groundwater level is greatly increased reaching a situation of high vulnerability in terms of contamination processes. From these results, we conclude that scenarios #2 and #3 are unfeasible as far as sustainable irrigation is concerned. www.witpress.com, ISSN 1743-3541 (on-line)