Flooding dynamics within an Amazonian floodplain: water circulation patterns and inundation duration
| Main Authors: | Sebastien Pinel, Marie Paule Bonnet, Joecila S. Da Silva, Thibault Catry, Frederique Seyler |
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| Format: | Proceeding |
| Terbitan: |
, 2020
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/3611590 |
Daftar Isi:
- Amazonian flood plains ensure fundamental hydro ecological functions and support a high level of biodiversity. Transformation in the Amazon basin, land use changes, dam construction and climate variability, increasingly threaten these emblematic ecosystems. In view of supporting their conservation, it is important to monitor the spatiotemporal distribution of key variables such as flood extent, inundation duration, and water velocities that constrain species habitats. However, floodplains are scarcely surveyed, and hydrological informat ion is commonly restricted to water level and discharge measured in the mainstream. As a solution, 2D hydrodynamics modelling allows monitoring these threatened zones and getting new information such as water circulation. Flooding dynamics across a medium size floodplain system (Janauacá Lake, 786 km 2 ) along the Amazon/Solimões River over a 9 years period (2006 2015) is studied through integration of remote sensing and limited in situ data in hydrologic hydrodynamic modelling based on Telemac 2D model. We f irstly detail the methodological approach and the modelling assessment in terms of water level, flood extent and velocity. It correctly reproduces floodplain water level (Nash Sutcliffe Efficiency=0.97) and flood extent (averaged Threat Score=62) and horiz ontal velocity (Nash Sutcliffe Efficiency >0.68). The model’s high accuracy varies along the hydrological year. Then, we focused on seasonal and inter annual spatial variability of water circulation and inundation duration. We highlighted strong heterogene ities in water velocity magnitude between the different morphological domains of the floodplain, the highest velocities being encountered in the river floodplain channel. In addition to topography, we emphasized the importance of the mainstream and the loc al runoff in controlling the water circulation, at least during part of the hydrological year. During the early rising period, local runoff constrains the river incursion across the floodplain, while the rates of mainstream rising/receding controls the flo od duration. The comparison of several hydrological years highlights the interannual changes of these hydraulic controls and also the influence exerted by prior inundation conditions. While we observed only few changes in water velocity distribution among hydrological years, the inundation duration is highly variable. Extreme flood events may induce positive (up to 40 days) but also negative (up to 20 days) anomalies of inundation duration.