Info regarding development of this Lot:
From Robert Myers - City of Webster Groves Planning & Development
To build a new house on the parcel, the floodplain standards would require that the lowest floor be elevated at least one foot above the base flood elevation. (Section 80.040.B of the Webster Groves Municipal Code, https://library.municode.com/mo/webster_groves/codes/code_of_ordinances?nodeId=PTVIIIOF_CH80FLDAPR) According to the Flood Insurance Rate Map available through the FEMA Map Center (https://msc.fema.gov/portal/search), the base flood elevation at this location is 446 feet above mean sea level. The current elevation of your lot, according to Lidar satellite date, is 436 feet above mean sea level. As the floodplain standards allow a garage to be located at ground level without elevating, the most likely scenario for rebuilding a house would be to build an elevated house with a an enclosed garage underneath at ground level. (The garage would have to have flood vents installed in the walls to allow water to flow through when flooded.) This new house design is quite common in flood zones. The maximum building height in the A4 District is two and a half stories, or 35 feet.   
 
Based on the size of the parcel and the existing A4 District zoning, which imposes a minimum 7,500 square foot lots, this parcel could conceivably be divided into two lots through a Lot Split Plat as prepared by a licensed land surveyor and approved by the Webster Groves City Council.