IWRA World Water Congress 2008 Montpellier France
6. Water Conservation and Demand Management
Author(s): Francisco rossarolla Forgiarini
Christopher Freire Souza
André Luiz Lopes
da Silveira
Geraldo Lopes da Silveira
Carlos Eduardo Morelli Tucci
PhD Student Institute of Hydraulic Research
– IPH, Federal University of Rio Grande do Sul – UFRGS, CNPq Grant Holder – Brazil. Address: Barão do
Amazonas, 1157/38, 90670-004, Porto Alegre – RS – Brazil, Telephone +55 51 33 08 63 27, Fax +55 51 33 08
75 0
Keyword(s): urban drainage charge, low impact development, Porto
Alegre - RS - BR
Article: PDFPoster: PDFAbstractIn recent decades, Brazilian cities have exhibited an accelerated and unplanned process of
urbanization, thereby producing negative impacts on water systems. Mechanism for encouraging the reduction of this
impact have been studied and implemented, taking as reference charges for the urban drainage service. The aim of
the present study was to investigate the application of different scenarios for the definition of a drainage fee applied
to hypothetical apartment complexes in the city of Porto Alegre – RS – Brazil. The methodology employed consisted
of analyzing fee values regarding construction enterprises according to the use of the rainwater drainage system. For
such, data were used from a study by Souza et al. (in press), who performed an analysis of hydrographs resulting
from different apartment complexes dimensioned in accordance with hygiene, compensatory and Low Impact
Development (LID) techniques in order to determine which responded better to the desire to maintain natural
hydrological conditions. The cost for solving the current problems of flooding in the city (Cruz, 2004) was averaged
among the apartment complexes according to fee scenarios based on the Total Impermeable Area (TIA), Effective
Impermeable Area (EIA) (Decree n° 15.371/2006, Porto Alegre; Shuster et al., 2005), alteration in volume and in
maximum natural runoff. One of the results of the study was the obtainment of an annual unit cost of R$ 0.49/m² to
finance, operate and maintain a system that would solve the current flooding problems in Porto Alegre. Thus, the fee
to be paid by the three apartment complexes was R$ 21,864.71. The results demonstrate that fee scenarios based
on TIA and EIA (according to Municipal Decree 15.371/2006) fail to encourage the adoption of sustainable
methods for the urban drainage planning. These scenarios resulted in practically equal charges for all the apartment
complexes without assessing alterations in natural runoff characteristics. Charges based on the scenario of alterations
in maximum runoff encourage planning through both the compensatory method as well as LID. Planning lots through
LID provides a lower fee in all scenarios, especially when charge scenarios regard the volume of surface runoff and
EIA (according to Shuster et al., 2005). This result was obtained because the effective production of runoff was
assessed in these scenarios. Thus, the adoption of drainage charges based on the production of surface runoff is the
most adequate alternative to encouraging a reduction in the impact of urbanization on the hydrological cycle in
relation to the assessment criteria of impermeable areas.