Morfologia e dinâmica de médio (1958-2010) e curto (2007) períodos da planície costeira de Almofala, Município de Itarema, Ceará

Abstract

This study also a morphologic and dynamic analysis in mid-term (1958-2004) and low-term (2007) to Almofala coastal plain (NW of Ceara, Northeast Brazil), including Almofala, Barreira and Torroes Beachs conditioned for high temperatures (>25ºC), media raining of 1172,21 mm, velocity winds of 5,5 m/s, mesotidal coast (media of 1,48 m), and height waves of 0,56 m. The objective also: (1) morphologic units and subunits identification (in scale 1:50000); (2) the evaluating shoreline changes by mid-term (1958-2010) and low-term (2007). The methodology consisted: (1) to compartment and subcompartment units, using the MDT and sloping map; (2) monitoring to coastal line in mid-term: with integration aerial photography’s and Quickbird images 46 years (1958/2004) and Landsat images, 33 years (1977/2010); (3) quantification and mapping to erosion and accretion zones; (4) morphosediment variability analysis by low-term (2007) to Almofala, Barreira and Torroes beachs; and (5) geoambiental zoning with vulnerability analysis and adjusting areas by using and occupation. In the PCA have this compartments and subdivisions: Plateaus (littoral “tabuleiros” with 8031957 m² and abrasion platform - 34654 m²; Coastal Plain (alluvial plain with 944912 m²; estuarine plain - lagune plain with 1449466 m², ebb-tidal plain 66696 m², tidal channels with 847036 m² and delta with 66696 m²; and sandy plain (coastal sandy dunes with 15343353 m² and beachs with 837031 m²). During period studied (1977/2010 - 33 years) the Almofala shoreline migrated so much, as continent direction as ocean direction: (1) section 3.1 -shoreline retreat of 785 m, with annual erosion rate of 13,15 m/years, retrograding -1,3 Km²/46 years (1958/2004), and addition of 570 m , prograding 888.045,47 m²/46 year, with annual rate of 6,3 m/year; (2) section 3.2 - the shoreline retreated 668 m, by erosion rate 12,24 m/year, retrograding -0,98 km²/ 33years (1977/2010), with addition 394 m, and accretion rate of 8m/year, prograding 0,37 km²/33years. The Almofala, Barreira and Torroes beachs behaved the beachs itself with RTR dominate wave. The parameter ε showed longshore bar and runnel to Almofala and Torroes beachs, with fine grain sizes (44%), and reflective to Barreira beach, with median grain sizes (29%). The parameter _ has stages lowtide terrace intermediate to Almofala beach and dissipative to Barreira and Torroes beachs. This beachs is semi-exposed by winds and waves, with erosion to Barreira (-64,5 m³) and Torroes (-72,1 m³) beachs, and acretion (62,83 m³) to Almofala beach (2007). The Torrões beach have high vulnerability by environmental risks (erosion), the Barreira beach have media as high vulnerability and the Almofala beach have media vulnerability to west and low vulnerability to east. The geoambiental map include: major APP’s areas, risky areas, appropriate occupation areas; and degraded areas for natural process (coastal erosion) and anthropic process to contribute with environmental planning and coastal management.