2.2. Hydrological aspects of the basin
The drainage Cunha Canal watershed comprises an area of
approximately 62.85 km2 and a perimeter of approximately
37.01 km.
The shape index and compactness index (Christofoletti, 1980)
calculated for the Canal do Cunha are 0.36 and 1.28, respectively,
which comprises a circular area that is subject to flood peaks due
to a smaller time of concentration (128.3 min) and the potential
for heavy rain to cover the entire basin.
Its drainage density is 0.54 km/km2 (Christofoletti, 1980). A
comparison of thisvalue with the results in Table 1, which was
developed by Christofoletti (1969) quoted by Silva et al. (2003),
indicates that the Faria-Timbó River basin has a low drainage density.
The high levels of urban occupation in the area, which reduces
the rate of infiltration and physiographic changes caused by the
construction of landfills, promotes an increased surface runoff
coefficient of 0.74.
According to the Köppen classification, the study area is characterized
as a hot and humid tropical climate (Fig. 3), which is characterized
by rainy summers from December to April and dry
winters from June to August. Thus, the discharge of fresh water
to the bay varies from 33 m3/s in the dry season to 186 m3/s in
the rainy season (Kjerfve et al., 1997). This characteristic demonstrates
the annual variation in saltwater dilution year