Outflow adjustment coefficient for the design of storage facilities using the rain envelope method applied to Brazilian state capitals

  • Diego Marangoni Santos Instituto de Pesquisas Hidráulicas. Departamento de Hidromecânica e Hidrologia. Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Gonçalves, n° 9500, Caixa Postal 15029, CEP: 91501-970, Porto Alegre, RS, Brazil.
  • Joel Avruch Goldenfum Instituto de Pesquisas Hidráulicas. Departamento de Hidromecânica e Hidrologia. Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Gonçalves, n° 9500, Caixa Postal 15029, CEP: 91501-970, Porto Alegre, RS, Brazil.
  • Fernando Dornelles Instituto de Pesquisas Hidráulicas. Departamento de Hidromecânica e Hidrologia. Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Gonçalves, n° 9500, Caixa Postal 15029, CEP: 91501-970, Porto Alegre, RS, Brazil.
DOI: https://doi.org/10.4136/ambi-agua.2707

Abstract

Detention devices are often used as alternative measures for stormwater control. The Envelope Curve Method is widely used in Brazil to estimate detention device volumes. This method estimates the storage volume based on inlet and outlet balance, where the inlet is obtained by the Rational Method and the outlet by orifice bottom discharge. Usually, the outlet flow is adopted as a constant and equivalent to the maximum allowed, and this procedure can cause reservoir undersizing. This paper evaluates detention control measures’ hydraulic behavior for the Envelope Curve Method and proposes the inclusion of an outflow adjustment coefficient (Cout), seeking to compensate for the adoption of constant outlet flow simplification. Values for this coefficient were estimated for several Brazilian state capitals, ranging from 0.62 up to 0.65. The undersizing hypothesis due to the adoption of constant outlet flow was confirmed, as the simulations showed the need for an increase between 8.4% to 16.8% in the device size. This undersizing may be compensated for by applying the outflow adjustment coefficient (Cout).

Keywords: adjustment coefficient, detention facilities, envelope curve, hydrologic design outflow adjustment coefficient.


Published
23/11/2021
Issue
Vol. 16 No. 6 (2021)
Section
Papers

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