Acta Limnologica Brasiliensia (Jun 2013)

Hydrosedimentological disequilibrium in a small, urbanized watershed

  • Alexandre Marco da Silva,
  • Alexandre Ribas dos Santos,
  • Rodolpho Augusto Fernandes,
  • Rodrigo Custódio Urban,
  • Romulo Martins Carvalho,
  • Luiz Augusto Manfré,
  • Steven Frederick Durrant

DOI
https://doi.org/10.1590/S2179-975X2013000200005
Journal volume & issue
Vol. 25, no. 2
pp. 140 – 149

Abstract

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AIM: In this paper we estimate the sediment yield and other related information for a small urbanized watershed, located in Sorocaba, São Paulo State. The driving forces that produce the observed scenario are presented and discussed; METHODS: Over a year, water samples and hydrologic information concerning the river channel were collected monthly at one sampling site. In the laboratory, water samples were oven dried (80 ºC) and the total suspended solid weighed for each sample. To estimate sediment yield we used Colby's simplified method. The sediment delivery ratio (SDR) was estimated using two methods: the relief - length ratio and the bifurcation ratio; RESULTS: The annual sediment yield estimated for the period was 1,636.1 t. The total specific sediment yield was 541.7 t.km -2.y-1. Bedload was the predominant fraction. The SDR changed between 60 and 66% according to the method employed. CONCLUSIONS: The main driving forces of hydrosedimentological disequilibrium are the lack of riparian vegetation, the dumping of construction wastes at inadequate sites, and the launching of untreated sewage. Hence, if these three factors were controlled, a significant improvement in the environmental quality, particularly water quality, might be achieved.

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