A Schematic Equivalent Topography Model of the Lower Paraná Basin based on Satellite Estimations and a Simulation Model

Abstract:

Flooding is a major concern in the Plata Basin. In particular, Paraná River has a long and wide floodplain, which has been settled and cultivated. Losses due to floods in Argentina during the 1983, 1992, 1998, 2007 and 2009-2010 floodings exceeded US$1 billion each. Therefore, providing information about the basin hydrologic condition in a systematic way is critical to the regional economies and society. In particular, monitoring basin fluvial wetlands’ flood-drought cycles is of extreme importance. These ecosystems extend along the Paraná-Paraguay axis and have highly dynamic exchanges of water with the river, with large annual and interannual variations. Thus, both floodplain water level and flooded area become relevant proxies for the total volume of water inside the floodplain. Moreover, the dynamics of these variables will be a raw indicator of floodplain overall hydrological behavior. Therefore, estimating these variables in a systematic way using remote sensing data, it is possible to constrain the outputs of hydrological forecast models.

The aim of this work is to construct an equivalent topography schema that can be incorporated to forecast and alert models of the basin. This is approached in three successive steps. First, we implement a methodology to estimate flooded area and water level inside the floodplain, based on active and passive microwave satellite data and a surface emissivity model. Then, we study the behavior of the flooding and low water phases through the analysis of the relationship between flooded area fraction and water level inside the floodplain obtained in the first step and between flooded area fraction and water level in adjacent water bodies obtained from hydrometric gauges and microwave altimetry. Finally, from the observed dynamics and a topographic simulation model we propose a schematic equivalent topography of the floodplain that represents the simplest topography that can explain the water dynamics observed during flooding events (See Figure 1).

In summary, the approach used on this work allows for the analysis of current hydrological condition in terms of its location in the flooded area vs water level diagram, and the posing of different possible future flooding scenarios, which would be useful for flooding forecast and alert.