O conhecimento da intensidade dos processos erosivos contribui para o planejamento ambiental de bacias hidrográficas, especialmente das bacias inseridas no contexto de semiaridez do Nordeste brasileiro, como é o caso da bacia hidrográfica do rio Coreaú, localizada na porção Noroeste do estado do Ceará. Este estudo tem por objetivo estimar as perdas de solos da bacia hidrográfica do rio Coreaú através do emprego da Equação Universal de Perda de Solo (USLE). O fator de erosividade das chuvas foi calibrado a partir de análises estatísticas de séries históricas de precipitações pluviométricas nos postos inseridos no interior da bacia em questão. As demais variáveis da Equação Universal de Perdas de Solos foram obtidas por meio de Sistema de Informação Geográfica (SIG), destinado à análise geoespacial da bacia hidrográfica. Em síntese, os resultados das análises obtidos pela USLE, demonstram que na bacia do rio Coreaú perde-se, em média, 15,80 t.ha-1.ano-1 de solos, sendo que que 993,709 Km2 da bacia do rio Coreaú apresentam perda anual de solo acima de 50 t.ha-1.ano-1, o que equivale a 9,4 % da área da pesquisa. Nessas áreas, os processos erosivos são bem mais intensos e, muitas vezes, ocorrem diretamente sobre a rocha exposta, pois o solo já foi totalmente carreado.

A linha de costa é uma feição geomorfológica em que as mudanças topográficas podem acontecer ao longo de horas ou dias devido a ocorrências de eventos de alta energia. Essa feição é de importância estratégica para o planejamento ambiental das cidades costeiras, sendo necessário o seu monitoramento contínuo. Este estudo propõe analisar a variação da linha de costa na praia do Icaraí, litoral de Caucaia – CE, a partir da aplicação dos métodos Digital Shoreline Analysis System (DSAS) e Polígono de Mudança. O recorte temporal de análise está compreendido entre os anos de 2004 e 2018, pois o agravamento da erosão se deu particularmente nos anos 2000. Os resultados demonstram que os deslocamentos médios da linha de costa, tanto para o DSAS (-3,72 m) quanto para o Polígono de Mudança (-3,41 m), se mostraram muito próximos. No entanto, quando observados parâmetros estatísticos mediana, desvio padrão e deslocamento mínimo e máximo foi observada uma superestimação das taxas obtidas pelo DSAS. A partir de uma análise de regressão linear foi observado que o Polígono de Mudança (R² = 0,9471) se mostrou mais adequado, pois considera todo o segmento costeiro nos cálculos de deslocamento. Tendo em vista os adjetivos e limitações dos métodos empregados, o Polígono de Mudança apresentou um melhor desempenho tanto em termos estatísticos quanto aos erros inerentes. Por fim, estudos de abordagem comparativa entre métodos são de grande importância para os gestores, visto que muitos municípios costeiros do Ceará e do Brasil têm apresentado problemas sérios ligados a erosão costeira. Study of the shoreline behavior at Icaraí beach (Caucaia, Ceará), using digital shoreline analysis system and the change polygon methods A B S T R A C TThe shoreline is a geomorphological feature with variable topographic and subject to changes vary very quickly in the time-space scale, and may present major changes in a few hours, as in the occurence of storm surges. This feature is of strategic importance for the coastal cities environmental planning, being necessary its continuous monitoring. This study aims to analyze the shoreline variation at Icaraí beach, Caucaia – CE coast, using two different methods: the Digital Shoreline Analysis System (DSAS) and the Change Polygon method. The analysis time frame is comprised between the years 2004 and 2018, since erosion worsened occurred particularly in the 2000s. The results showed that the average displacements from the shoreline, both for the DSAS (-3.72 m) and to Change Polygon (-3.41 m), were very close. However, when the other statistical parameters were observed (median, standard deviation, minimum and maximum displacement), an overestimation rates obtained by DSAS was observed. A linear regression analysis showed out that the Change Polygon method (R² = 0.9471), proved to be more suitable for the Icaraí beach, as it considers the entire coastal segment in the calculation of shoreline displacement. Although both methods approaches have their adjectives and limitations, the Change Polygon showed a better performance, both statistical terms and in relation to inherent errors. Finally, studies that take into account the comparative approach between methos are of great importance for managers, given that many coastal municipalities in Ceará and Brazil have presented serious problems related to coastal erosion.Keywords: erosion, DSAS, change polygon, remote sensing.

Sandy beaches play a crucial role as natural barriers against climate change and hold significant socioeconomic value. In the municipality of Icapuí, on the eastern coast of Ceará, erosion has affected some of its beaches since the 2000s, impacting structures near the Shoreline (SL), such as schools, inns, and residences. This article analyzed the SL dynamics on the beaches of Barreiras de Baixo, Barreiras de Cima, and Barrinha, located in the mentioned municipality, using two scales of analysis: in the short term, with in situ surveys using geodetic receivers between 2015 and 2023, and in the long term, with orbital images from 2002 to 2024. For statistical analysis, the End Point Rate (EPR) and Linear Regression Rate (LRR) methods were applied in ArcGIS software using the Digital Shoreline Analysis System (DSAS) version 5.1 extension. The short-term analysis revealed an average EPR of 0.0 m/year, with a maximum progradation of 7.1 m/year and maximum erosion of 6.4 m/year. The LRR showed an average of -0.2 m/year, with a maximum progradation of 7 m/year and maximum erosion of 6.7 m/year. The long-term analysis showed an average EPR of -1.1 m/year, with a maximum progradation of 0.5 m/year and a minimum erosion of 3.9 m/year, while the LRR indicated an average of -0.7 m/year, with maximum erosion of 3.6 m/year and maximum progradation of 1.6 m/year. These results indicate a more pronounced retreat of the SL over time. The analysis also revealed that containment structures, such as Rip-rap, have replaced wooden stakes and sandbags previously used by local communities, stabilizing 63.2% of the SL. The forecasts obtained through this study for the years 2034 and 2044 indicate shoreline retreat in areas still without protection, highlighting the urgent need for effective participatory planning. It is essential to align this planning with the Municipal Climate Change Adaptation Plan and the Integrated Coastal Management Plan (ICMP). Maintaining protection structures and conducting continuous monitoring is crucial to adapting coastal management strategies, protecting vulnerable communities and ecosystems.

This article presents the results of an analysis of the social and recreational value of waves at Icaraí Beach, located in Caucaia municipality, Ceará, Northeast Brazil. The evaluation of the wave resource followed the Zonal Travel Cost Method, a fundamental tool for obtaining economic estimates ​​of ecosystem services that are not subject to market forces. The method provides a valuation of unique abiotic resources that underpin tourism, sporting and recreational economies. For data collection, 50 questionnaires with open and closed questions were administered from February to July 2019 to a specific audience, the local surfers. The social value of Icaraí’s surf break is strongly related to the surfers' familiarity with the beach, as well as in the perception of the wave resource as a profitable attraction for the local economy. It is estimated that the economic benefit of the surf break at Icaraí Beach is US$ 288,364 per annum, which is spent by 1,185 surfers, averaging US$ 1.37 for each surf trip. In summary, the values ​​reflect economic benefits for the municipality of Caucaia and can assist decision-making processes, contributing to the protection and maintenance of the beach by incorporating wave resources into an effective coastal management strategy. Keywords: Value of waves. Surfers. Surfing. Cost of Travel Method. Coastal Management.