Begin by creating some housing and providing your people with water access and fire protection. Lay a section of road onto the flood plain and place Fig Farms on both sides of it. Floodplain farmers come from Work Camps, so be sure to build one nearby the floodplain farms. Work Camps negatively affect the desirability of the surrounding area, but must be placed near housing in order to gain employment. Once the Work Camp is staffed, laborers will walk to the floodplain farms and begin working.
Laborers look like employment walkers without hats.
Use the time before the flood to prepare your city for food distribution by building a Granary and some Bazaars. Laborers will harvest figs in August, but unless there is a Granary for them to take the food to, they will remain on the floodplain and drown when the floodwaters arrive. Once you have sufficient food in your Granary, some basic industry buildings will become available. Place a Clay Pit or two near the water or edge of the floodplain to begin clay production. Keep in mind that the citizens of your city do not want to live near these mud holes.