The Effect of Land Forming on Subsidence in the Florida Everglades' Organic Soil

Abstract

AbstractLand forming in the Everglades Agricultural Area (EAA) can become an important practice for reducing the organic soil subsidence. Before the land forming practice can be successfully implemented in the EAA, ground elevation variation with time, concepts of ground elevation distribution, and managing different types of water table depth need to be clearly defined. A new concept of general low spot elevation was introduced. It was estimated from general deviation of ground elevation, composited from 68% of 1 standard deviation (SD) of ground elevation, 27% of 2 SD, and 5% of 3 SD. Three types of water table depths involved in this study, which were used to evaluate the impact of land forming on reducing subsidence, were conventional water table (CWT), recommended water table (RWT), and unifrom water table (UWT). The results showed that the SD of ground elevation in virgin land decreased from 6.2 cm in 1958 to 2.6 cm in 1978. the St. Augustine grass (Stenotaphrum secundatum) field had a similar trend of decrease in SD from 3.6 cm in 1958 to 2.6 cm in 1978. As the time progresses, the range of ground elevations decreases. The ground elevation in EAA is approximately a normal distribution because the probability distribution in ground elevation is similar to normal condition. The land forming has the potential of extending the life of organic soil by about 10 years in EAA with either RWT or UWT management conditions.