Investigation and Assessment of the Demarcation Method for Federal Riverine and Accreted Lands: Case Study of the Rio de Janeiro State Section of the South Paraíba River

To support land use and environmental planning, government planning and especially continuous monitoring are essential. When there is no such supervisory action, population occupation and expansion can occur in areas belonging to the federal government or in areas that should be preserved, thus impairing the social and environmental balance. This study analyzes the demarcation method of riverine and accreted land of the Brazilian Federal Heritage Department and proposes the incorporation of the flow rate corresponding to the recurrence interval of two years, as recommended by the State Environmental Institute of the state of Rio de Janeiro. The case study of the Rio de Janeiro section of the Paraiba do Sul River was investigated, and the results indicate that the Federal Heritage Department’s method does not consider the ongoing anthropization of the river, caused mainly by the construction and operation of hydroelectric plants. In addition, it was observed that the limnimetric scales of the studied gauging stations are influenced by constant changes in the riverbed and by riverbank occupation, making it difficult to estimate the ordinary flood level. The study concludes by suggesting the adoption of a flow rate with a recurrence interval of two years and the simulation of the runoff conditions for demarcation of the average ordinary flood line. It is believed that the demarcation of the MOFL along a river should not be evaluated individually at each gauging station or site of interest because the river has its own dynamic flow. Thus, future studies should model the hydrodynamic runoff conditions of the Rio de Janeiro section of the Paraíba do Sul River to establish the water levels corresponding to floods with an RI of 2 years and then confirm these levels on site through topo-bathymetric surveys.