The municipality of Belém is installed on low ground under a rich and immense system of surface waters that converge for the most part directly into the Pará River system, Marajó Bay, northern fathom of the Amazon River and then the Atlantic Ocean. The Guamá river (estuary) and Guajará bay stand out, bathing its western, north and northeast portions, and numerous tidal channels, as well as several streams converge on the former, as well as several swamps and temporary wetlands. The main urban nucleus, the city of Belém, was installed and continues to do so, along the tidal and igarapé channels, modifying its courses, and polluting them brutally, either by solid waste or by domestic effluents of all kinds without any treatment, in addition to industrial contributions, becoming more serious as the city moves forward in horizontal and vertical buildings. The tides partially assist in this cleaning, by carrying a large part of these pollutants daily to the Guamá River, from this one to the Guajará Bay and then Marajó and Atlantic. Beautiful beaches in the north and northeast of the municipality (Outeiro, Mosqueiro, Farol, Ariramba, Carananduba, Paraíso and Baía do Sol) attract thousands of visitors, which further contribute to general pollution. Although several surveys have already been carried out to assess these impacts and its dilution, it was decided to try a new attack, emphasizing the Tucunduba stream and its drainage in the Guamá river, the Guajará bay on its margin of strong industrial-port impact and then the beaches of the Baía do Sol. Water and solid sediment in suspension (suspended) were collected in three different periods, considering the two tidal cycles, in eight seasons. Measurements of the main physical parameters were made in loco. Next, cations and anions in the waters analyzed, mineralogical identification and chemistry of the suspensates, in addition to micromorphological analyzes were carried out. The results show that the Guamá river and Guajará bay can be still classified as unpolluted natural waters, similar to the white waters of the Amazon region. Tucunduba and the waters of the Baía do Sol, mainly those restricted (swamps and manholes) are strongly altered by human occupation. Cations and anions, as well as microplankton from the suspension sediments, also allow identify the seasonal interference of oceanic interference during the dry season. The suspension materials of these rivers are dominated by quartz, kaolinite, partly muscovite / illite, demonstrating a strong relationship with the sediments of the margins, gullies and flood plains, and also of the Barreiras Formation, Neogene in age, the geological unit that serves as a substrate for the lands of Belém municipality. However, for a more informed assessment, a systematic and much more comprehensive study is recommended from the chemical, biological, mineralogical point of view and still under strong seasonal and tidal cycle controls, preferably for a continuous decade.
Flood characterisation of the Haor region of Bangladesh using flood index
