Previsão de enchentes e análise da vulnerabilidade ambiental com base no uso e cobertura da terra na bacia hidrográfica do rio Meia Ponte, Região Metropolitana de Goiânia

Abstract

The Goiânia Metropolitan Region (RMG) faces significant environmental challenges due to disorganised urban growth in its municipalities. This urban expansion has caused environmental impacts in the Meia Ponte river basin (BHMP). Between 1985 and 2022, the urbanised areas of the municipalities that make up the RMG increased by 307.83%. This uncontrolled advance has resulted in the loss of native vegetation cover, soil sealing and compaction, intensification of surface run-off and an increase in the risk of flooding. A geomorphological analysis indicated that the predominance of degraded pediplains and soils susceptible to erosion aggravates environmental vulnerability, especially in valley bottom areas.Analysis of annual accumulated rainfall in the BHMP between 1990 and 2023 revealed variations of between 600 mm and 1,700 mm, with stabilisations in specific periods. Statistical simulation indicated that the time series is stationary, with the ARIMA(1,1,1) model being the most suitable for forecasting, estimating average annual rainfall of between 1,000 mm and 1,200 mm for the period 2024 to 2033. The hydrodynamic analysis of the floods shows that increasing the return time (10, 50, 100 and 500 years) increases the extent of the flooded areas, with depths of up to 10 metres in critical sections of the river. The velocity profiles indicated variations of up to 7 m/s over a 25 km stretch, reflecting the dynamics of the flow in the basin.The limitations in collecting data in the field (difficult-to-access stretches, inconsistent GPS signals, areas with low depths, water level variation), among others, contributed to an NSE (Nash-Sutcliffe Coefficient) of 0.509 and an R2 (Coefficient of Determination) of 0.875 for the water levels, showing moderate agreement with the observed data. However, for the flow, the NSE of 0.014, despite the high R2 (0.952), indicated difficulties in representing local variations. In addition, irregular occupation of the banks and the emission of effluents increase environmental risks, reducing the capacity of the river basin to drain large volumes of water. The results emphasise the need for integrated urban planning and mitigation actions, such asrestoring native vegetation, protecting permanent preservation areas and implementing publicpolicies aimed at sustainability. Collaboration between municipalities is essential to minimize the vulnerability of the RMG, reconciling urban growth with environmental conservation.