Navigation at the Amazon River Mouth: Sand Bank Migration and Depth Surveying

摘要

The Amazon River mouth represents a critical pass for navigation at one ofrnthe most important waterways in Brazil. Besides the economic importance ofrndiminishing the uncertainties of establishing the navigation depth, there is a strongrnconcern about the threat of oil spills and its environmental impact in this particularrnsystem. This work addresses to two related issues: the migration of sand banks andrnthe difficulties related to sounding reduction.rnAt the mouth region, the current loss of transport capacity propitiates sandrndeposition which will contribute to the reduction of depths and the formation ofrnbanks. Bathymetric records were analyzed and it was observed sand bank movementrnof approximately 250 m/year [1]. However, anything could be concluded about thernperiodicity of the bank change of migration direction and its causes.rnIn addition to the bottom variability, there is an intrinsic difficulty forrnestablishing the reference level due to the region’s great dimensions, variability andrnmagnitude of the tides and river discharge which influences mean sea water level andrntidal amplitudes. The sounding reduction is currently done by the Brazilian Navyrnthrough a simplified method [2]. In order to estimate the expected depth differencesrnthrough the use of a more realistic method, a hydrodynamic numerical model wasrnimplemented in the area. The mean differences observed, for low river discharge,rnwere 1.14m and maximum differences reached almost 3m (both negatives andrnpositives), which are significant values for such a critical area.