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Purpose: In the humid Caribbean region characterized by high intensity tropical rainfall, soil aggregate breakdown and pore blocking due to slaking pressures are major land degradation mechanisms. In this research, we investigated the susceptibility of soils to slaking pressures under rapid wetting as influenced by soil properties and the depositional origin from which the soil is formed using water stable aggregates (WSAr) and percolation stability (PSc) as indices of the strength of aggregate inter-particle cohesion.Materials and methods: Wet sieving and percolation stability analyses were employed to investigate WSAr and pore blocking, respectively. The combined effect of soil properties of clay, organic matter (OM), cation exchange capacity (CEC) and exchangeable sodium percentage (ESP) was used to determine the slaking sensitivity score (SSc) of fourteen physiogeographically important soils in Trinidad, comprising of nine alluvial and five residual soils.Results and discussion: Results showed that irrespective of alluvial or residual depositional nature of the parent material, samples had high SSc with an average WSAr of 37.8% and PSc of 6.0mm/10 minutes. The linear relationships between SSc with WSAr (r 2 = -0.12) and SSc with PSc (r 2 = -0.012) of all the 14 soils although negative were weak. Clay content accounted for 94.0% of the variation in CEC in alluvial soils and had a strong negative relationships with WSAr (r 2 = -0.74) and PSc (r 2 = -0.79) in residual soils. Additionally, OM with WSAr (r 2 = 0.52) and PSc (r 2 = 0.24), and CEC with WSAr (r 2 = 0.46) and PSc (r 2 = 0.39) showed significant positive linear relationships in residual soil. Conclusions:The predominantly micaceous and kaolinitic clay mineralogy of these soils coupled with the low OM contents, increase the proneness of the soils to slaking. This suggests 3 that clay mineralogy is responsible for the high slaking sensitivity rather than clay content or just the depositional origin of the soils. As CEC increases, an accompanying increase in OM is required to increase inter-particle cohesion and to impart partial hydrophobicity, which in turn decreases mineralogically induced susceptibility of individual aggregates to slaking.

Manzanilla beach in Cocos Bay, Trinidad is a barrier beach that protects the freshwater Nariva Swamp from the marine environment of the Atlantic. Manzanilla beach is a very dynamic system owing to the open bay morphology, and exposure to the Atlantic Ocean. This study evaluated the spatial and temporal morphological and sedimentological characteristics, alongside hydrodynamic conditions operating on the beach. It investigates the beach's response to tidal cycles diurnally, from spring to neap tide, and seasonally. Data from nine sites during the period December 2005 to September 2007 are analyzed. Coastal parameters such as beach profiles, littoral data and sediment samples were obtained using standard geomorphological techniques. Beach volumetric changes that occurred over the tidal cycles are also quantified. Results indicate that wave height and wave energy were good predictors of beach change. The study showed that erosion was linked to rising tide and accretion to falling tide diurnally. Erosion occurred during spring tide conditions and accretion dominated during neap tides. Seasonally more erosion occurred in the winter period (dry season) and beach changes in the summer period (wet season) were controlled by the formation and migration of bars. Beach Morphological Dynamics at Cocos Bay (Manzanilla), TrinidadJunior Darsan rÉsUMÉ La plage de Manzanilla qui donne sur la baie des Cocos dans l'île de la Trinité est un cordon littoral qui protège le marais d' eau douce de Nariva en faisant écran entre celui-ci et l' environnement marin de l' Atlantique. Le système de la plage de Manzanilla est très dynamique en raison de la morphologie de la baie échancrée et de son exposition à l' océan Atlantique. L' étude évalue les caractéristiques sédimentologiques, morphologiques, spatiales et temporelles de la plage, ainsi que les conditions hydrodynamiques qui y sont à l' oeuvre. Elle examine l' effet sur la plage des cycles diurnes et saisonniers des marées, depuis les marées de vives-eaux jusqu'à celles de morteseaux. Les données prélevées à neuf endroits pendant la période allant de décembre 2005 à septembre 2007 sont analysées. Les paramètres côtiers, comme les profils de la plage, les données sur le littoral et les échantillons de sédiments, ont été obtenus au moyen de techniques couramment employées en géomorphologie. Les changements de volume qui sont survenus sur la plage pendant les cycles des marées sont aussi quantifiés. Les résultats révèlent que la hauteur et l' énergie des vagues sont de bons prédicteurs des changements subis par la plage. L' étude a montré que l' érosion est associée à la marée montante et l'accrétion, à la marée diurne descendante. L' érosion est survenue pendant les marées de vives-eaux et l'accrétion se produisait plus souvent durant les marées de morteseaux. Par rapport aux saisons, il y avait plus d' érosion en hiver (saison sèche) et les changements subis par la plage pendant la période estivale (saison des pluies) étaient tributaires de la formation et de la migration des barres.[...