Shovel-dug test trench illustrates soil disruption that occured in ancient times; perhaps an attempt to channel standing water or to raise growing beds above the soggy swamp. Either way, ground water stands at about 16-21" below surface during dry season! This trench would certainly be full of water during the summer rainy season.

Also notice how nutritionally poor-looking the soil is. This "marl" consists of varying amounts of calcium carbonate, clay, and silt size material. Dark stains are the remains of organic matter.