The experience of going into this place would be, a person would have to use the ramp to pass the store/restaurant entrance, before ascending to the residential area. This very idea of circulation was taken from RU-KO(store-house) placement, where the lower level serves as public area (store, small shop) and the higher level is for living (Private area) . Historically and traditionally, people would gather and socialize in lower level of the structures, while the higher become more secluded and private area.
Open underground lower level is make sense for comfort level by lowering the temperature for the pedestrians, and this system will also allowed the high water to re-channel and pass through.
Small Floods.
During High Floods condition.