**3.2 Coastal environmental problems in Fortaleza area**

The Mucuripe headland, in Fortaleza city, is characteristic of a low-lying (~1.5 in mean tide) outcrop of Precambrian quartzite (**Figure 2A**). It trends ESE-WNW and has been heavily engineered since the 1950s, following the installation of a harbor (**Figure 2B**).

The longshore current and transport of sand in the area take place from east to west. The sands, before the installation of the harbor, bypassed the headland and were transported to the west, nourishing the beaches downdrift, for dozens of kilometers. The two extensive jetties built to protect the harbor from waves and silting interrupted the longshore current, eliminating the transport of sediments downdrift [4, 12, 16–18]. Quantification of the sand intercepted by the headland and harbor structures yielded a reasonably accurate estimate of longshore sand transport rate of approximately 860,000 m3 /y [12].

This interruption of littoral drift induced a large accumulation of sand updrift, of the order of 825,000 m3 /y [16, 19]. Since the installation of the harbor, the total amount of sand accumulated updrift is approximately 26.4 million m3 , creating a new beach of 65.5 ha of area (Serviluz beach, for location, see **Figure 2B**) [16].

However, part of the sand accumulated in Serviluz beach, despite the jetties, bypasses them and the headland, being transported around these features and deposited by wave diffraction along the northern side of the harbor, creating the Mansa Beach and silting the harbor's basin (**Figure 3**). For this reason, dredging is frequently needed in the harbor basin, in order to let large boats dock without stranding. Surveys carried out by [16] indicated that the amount of sand dredged from the harbor's basin since the 1950s is of the order of 21 million m3 .

#### **Figure 2.**

*(A) Mucuripe low-lying headland, in Fortaleza city, a natural feature that changes the orientation of the shoreline, from SE-NW to NE-SW. (B) The Mucuripe/Fortaleza harbor, installed in the 1950s, and the jetties built to protect the harbor's basin from waves and silting. The jetties interrupted the longshore transport, which came from the east.*

*Environmental Problems and Coastal Mitigation in South America: Examples from Northeast… DOI: http://dx.doi.org/10.5772/intechopen.87959*

#### **Figure 3.**

*The residual bypass of sand across the jetties and the headland created the Mansa Beach and keep nourishing it regularly. The bypass also produces the silting of the harbor's basin, which has to be frequently dredged.*

#### **Figure 4.**

*Jetties installed in Fortaleza coastal area, in order to protect the shoreline against the erosion resulted from the interruption of the longshore transport produced by the harbor and associated jetties constructed updrift (east of the shown area) (source: Google Earth, 2019).*

#### **Figure 5.**

*(A). East coast of Fortaleza city and Mucuripe harbor vicinity, with large dunefields. The red arrow shows the area where the bypass of dunes still took place after the construction of the harbor. (B). Complete urbanization of the dunefields, with cessation of dunes bypass.*

The aggressive interruption of the tremendous amount of net longshore sand transport has induced up to 100 m of beach erosion downdrift of the headland/ harbor between 1960 and 1970 [17]. Numerous shoreline structures, such as groin fields, were constructed to protect the shoreline from this beach recession (**Figure 4**), further disrupting the longshore sand transport system and extending the artificial influence further downdrift [12, 17].

In addition to the blockage of longshore bypassing, the dune bypass is also completely obstructed by buildings densely constructed over the entire area during the last decades [4] (**Figure 5**). Practically no sand reaches the downdrift beach through headland dune migration anymore [4] or through the flux of the Ceará river mouth,

to where the dunes of the western segment of Fortaleza city migrated before [16] (for location of Ceará river estuary, see **Figure 4**).

The consequences of these processes in the coastal dynamics are dramatic. The shoreline retracted some 400 m in 60 years at places 15 km from the headland [4, 13]. The erosion is still happening: In Icarai Beach, 25 km downdrift, beach recession of magnitude of 100 m took place between the years 2004 and 2016 [4].

The retraction of the beaches indicates that the coastal dynamics in the area are completely disturbed. The sand introduced in the littoral drift by means of this erosion is the probable source of the sediment that is now accumulating in the area around the pier of another harbor, the Pecém harbor, located in the next headland downdrift, 60 km west of Fortaleza harbor [4]. The degradation illustrates the changes related to extreme human interventions on a unidirectional system, associated with rising sea level.
