Overflow risk analysis on the Presidente Dutra highway using the quota-volume curve in the Una River Basin in Taubaté, SP, Brazil

Paulo Sérgio Dos Santos ,Marcelo Dos Santos Targa,Celso De Souza Catelani,Eduardo Rodrigues Dos Santos ,Nelson Wellausen Dias ,Marcia Eliza De Godoi Dos Santos

doi:10.4136/ambi-agua.2580

Abstract

Anthropic interventions and vectors of urban occupation have caused changes in the infiltration and runoff regime that can cause or accelerate erosion processes, silting and flooding in river basins. Flooding, as a stochastic phenomenon, can occur at any time and in any place, influenced by climatic factors, physical characteristics of the basin and mainly by human interference in the use and occupation of the land, which affects the type, quality and quantity of vegetation and increases soil impermeability. The aspects of regional urbanization led the State in 2012 to create the Metropolitan Region of Vale do Paraíba and the North Coast (RMVPLN), attracting large real estate investors. In the hydrographic basin of the river Una in the municipality of Taubaté, there has been an increase in flooding episodes and the possibility of worsening due to changes in land use and occupation. In this study, we sought to determine runoff as a function of changes in land use and occupation expressed by the variation in runoff coefficient (C) recommended by the Department of Water and Electricity of the State of São Paulo, (DAEE-SP) for licensing and intervention projects in water resources. The lower limits C = 0.35 and upper C = 0.70 were used admitting variations of 0.05 points in this interval to calculate the water flow (QE) and Intake Volumes (VE) in the basin from an intense precipitation of 100 years of recurrence time, from the use of the UEHARA Method (DAEE, 2006), to the control point located at the intersection of the Una River and the Presidente Eurico Gaspar Dutra Highway (BR 116-SP) and from this the Quota-Volume curve was drawn. The flood shares were obtained by hitting the reserve volumes found on the quota-volume curve.The current runoff coefficient of the basin is C = 0.35, which allows water to pass through the Dutra highway bridge. However, the modification of C = 0.50 due to the advance of urbanization, the level of flooding would reach 557.40 m. That exceeds the level of the lower base of the bridge (556.72 m) and, with C = 0.60, would reach the quota of 558.90 m, which would cover the asphalt surface of the highway. Given the real estate pressures in the metropolitan region, special care is recommended in the conservation, preservation and expansion of native forest vegetation with actions for Payments for Environmental Services (PSAs), de-silting actions of the main gutter and Una's tributaries, to contain the identified advance of urbanization in the basin, as well as the definition and installation of detention and retention basins.

Highlights

Brazil is one of the countries most affected by floods (Souza et al, 2017), which are characterized by the overflow of water from watercourses from their natural beds to marginal areas
We used the adaptation of the Quota-Volume Curve methodology (DAEE, 2006) applied to small basins to determine the quota to be reached on the Presidente Eurico Gaspar Dutra Highway (BR116/SP) at the crossing with Rio Una in the municipality de Taubaté, SP, due to precipitation with 100 years of return
When calculating the maximum flood flow, the risks inherent to the Presidente Dutra Highway are considered after a precipitation with a statistical possibility of occurring once every 100 years

Summary

Introduction

Brazil is one of the countries most affected by floods (Souza et al, 2017), which are characterized by the overflow of water from watercourses from their natural beds to marginal areas.The increase in the frequency and intensity of flood events may be associated with anthropogenic activities that cause environmental degradation in river basins, such asRev. Brazil is one of the countries most affected by floods (Souza et al, 2017), which are characterized by the overflow of water from watercourses from their natural beds to marginal areas. Disordered urbanization (Tasca et al, 2017), the industrialization, deforestation and occupation of improper areas (Sousa and Gonçalves, 2018) and the insufficient capacity of many hydraulic structures. Among these structures are large and small dams, bridges, culverts, drainage systems, mainly on highways and railways. Given that many of these structures are from the 1950s, changes in land use and occupation interfere in the dynamics of water in the basin, mainly in the infiltration and runoff processes

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