Measuring connectivity in floodplains rivers: application of FITRAS function to the lower Paraná

Abstract

In major rivers with extensive floodplains, the exchanges between the main channel and the floodplain are the main force that organizes the structure and maintains the stability of the landscape. The time period of flooded soil at each point on the floodplain indicates the extent of connectivity of each landscape with the river´s main channel. However, not all populations and organisms and river processes are stimulated (or limited) by these pulse characteristics in the same way. Pulse attributes are synthesized with the function FITRAS, an acronym for Frequency, Intensity, Tension (or Stress), Regularity (or Recurrence), Amplitude and Seasonality. Hydrological variability in a time series is represented by the curve visualized as a sinusoidal function, and the overflow level defines the connectivity of each site by assigning the values of the historical series as "positive" to those that exceed the reference level, and "negative" to the records that are below that overflow line. In this contribution, we provide a discussion of processes related to pulse attributes and a simple procedure for assessing ecohydrological connectivity in river floodplains using the Pulso software, as well as complementary tools for assessing the predictability of cyclical components of the hydrograph and their relationship to vegetation distribution.