In riverine situations, the floodplain is divided into which two parts?

In riverine situations, the floodplain is indeed divided into two main components: the floodway and the flood fringe. The floodway is the area of the floodplain that is closest to the river. It is typically the most hazardous part of the floodplain, as it is where water flows during a flood event. Development in this area is often restricted or regulated to maintain the flow of water and reduce flood risk.

On the other hand, the flood fringe is the portion of the floodplain that is outside of the floodway and typically experiences lower flood risk. This area can still be subject to flooding but is generally less hazardous than the floodway. The distinction between these two components is crucial for floodplain management, as it helps planners and emergency officials make informed decisions regarding land use and flood mitigation strategies.

The other choices presented do not accurately reflect the components of the floodplain. Upland and lowland are broader geographic terms that aren't specific to floodplain delineation. Wetland and dryland refer to types of land based on moisture levels and ecological features rather than flood risk. Base flood elevation and wave height pertain to flood measurement parameters but do not describe the geographical divisions within a floodplain.