Physical and vegetation characteristics of soil cover on a liquefied land

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Liquefaction is a phenomenon where a solid soil becomes liquid due to an earthquake or other vibrations and other sources of intense shaking, leading to a loss of soil strength and stiffness. Liquefaction can damage structures and condition of the land surface and may affect the state of the vegetation that grows on the land. Therefore, it is necessary to study the physical properties of the soil and the condition of vegetation after the liquefaction event. This study examines changes in the physical conditions of alluvial soil and vegetation cover on the land surface after the liquefaction disaster and future management strategies. This research was carried out from August to December 2022 by taking composite and representative soil samples from three land conditions, namely liquefied land consisting of eroded and piled up soil, as well as a control sample from ground that was not liquefied. Soil sample analysis was conducted at the Laboratory of Soil Science, Faculty of Agriculture, Tadulako University. The research used several observational variables: soil texture, permeability, bulk density, porosity, and organic matter. Observation of land surface cover and vegetation types was done using the quadrant method. The results indicated that, overall, areas affected by liquefaction experienced a substantial loss of soil mass, leading to a lower land surface, particularly in regions prone to erosion. Due to the erosion of surface soil, the remaining subsoil had a sandy loam texture, higher bulk density, increased permeability, and reduced organic matter content. As a result, the ground surface became undulating, with mounds of soil and irregular surface drainage in certain areas. For areas that experienced liquefaction up to four years after the disaster, the level of land cover only reached 60-61%. In contrast, the level of land cover by surface vegetation reached 93.7%.