Hydrodynamic Characterization of the Flood Pulse in a Shallow Tropical Wetland

Abstract This study addresses the flood pulse of tropical wetland systems from a hydrodynamic perspective to achieve an understanding of the intrinsic physical processes involved in their water dynamics. The hydrodynamic perspective can offer a detailed understanding of physical processes associated with tropical wetland system water dynamics. To this end, a numerical hydrodynamic model based on the shallow water equation (SWE) has been used. It identifies unique flood pulse patterns to help understand interactions and dynamics within the river‐wetland system. The area for this study of flood pulse dynamics is the interconnected system of the Cauca River and the El Palomar wetland. The ”flood pulse concept”, proposed by Junk, Bayley, and Sparks (1989), suggests that the flood pulse is crucial for controlling biota in tropical floodplains. This study’s findings identify two main phases in the system’s dynamics: the drawdown period and the wetland filling period. Each has distinctive characteristics based on water level differences between the river and the wetland. The emptying period begins as the river flow decreases, causing water to flow from the wetland to the river. This process can be divided in two: an initial period of accelerated increase of the water level difference culminating in a maximum flow of water from the wetland to the river, and a second period of decrease of this difference. Moderated by the river’s water flow, the second period is more gradual. It lasts until the river/wetland area equilibrium is restored. The second process begins as the river flow increases to the point when the river level rises above that of the wetland. This causes the water flow to reverse directions and begin flowing out of the river and into the wetland. This phase is also divided into two periods: a rapid rise in the hydraulic gradient, resulting in an increase in the wetland area, followed by moderation of the flow as the water level difference decreases as the system moves towards a new equilibrium. Both processes, emptying and filling, reflect the dynamic interaction between the river and the wetland, highlighting the importance of the flood pulse as a natural regulator of the hydrodynamics and ecology of these ecosystems