Morphometric and Morphological Analysis of Trindade Island, South Atlantic, Brazil

Abstract

Despite being well established in continental watersheds, morphometric analysis is still incipient in oceanic islands. Our goal is to analyze the morphometry and morphologically classify the island of Trindade, located in the South Atlantic. The parameters we used were altitude, slope gradient and aspect, LS factor, Topographic Wetness Index (TWI) and the Geomorphons classification. Trindade island has an altimetric amplitude of 600m, with 34% of its area between 0-100m and 21.2% in the 100-200m range. The island’s lower parts are gravel and sand beaches and alluvial fans. Ridgelines such as the Desejado and Verde peaks represent heights above 500m and occupy 2% of the island’s area. Slope gradients vary from strongly undulated (20-45%) to hilly (45-75%), with both classes occupying half the island’s area. Flatter areas (with slope gradients between 0-3% and 3-8%) occupy less than 4% of the island. The slopes more exposed to weather conditions (rainfall and winds) are the ones facing east and southeast, therefore being the most prone to evolutionary relief processes. The western and northwestern faces are steeper and more sheltered from the weather. The Geomorphons classification has shown that 57% of the island is composed by straight slopes, 19% are spurs (slightly convex slopes in plan and profile), and 18.6% are hollows. The TWI shows that the areas prone to saturation are relief concavities in medium to lower thirds of the slopes.

Keywords:
Oceanic Islands; Hydrology; Topographic Wetness Index; Geomorphons