FLOOD INUNDATION MAPPING FOR INTEGRATED FLOODPLAIN MANAGEMENT: UPPER MISSISSIPPI RIVER SYSTEM

Natural hydrogeomorphic characteristics and hydrologic alterations are important ecological drivers, and hydrology is also a common ecological, flood control and navigation system indicator. Hydrologic characteristics change dramatically from one end of the Upper Mississippi River System to the other, and hydraulic characteristics also differ spatially across the river channels and floodplain in response to dams, levees and diversions. Low flow surface water spatial change in response to navigation and flood control has been well known for many years, but little information was available on the spatial distribution of frequent floods. The flow frequency data presented here were developed to better estimate contemporary floods after historic flooding in 1993. Flood stage estimates are enhanced in GIS to help quantify and map potential floodplain inundation for more than 1000 river miles on the Upper Mississippi and Illinois Rivers. Potential flood inundation is mapped for the 50% to 0.2% annual exceedance probability flood stage (i.e. 2- to 500-year expected recurrence interval flood) and also for alternative floodplain management scenarios within the existing flood protection infrastructure. Our analysis documents: (i) impoundment effects, (ii) a hydrologic gradient within the navigation pools that creates repeating patterns of riverine, backwater and impounded aquatic habitat conditions, (iii) potential floodplain inundation patterns for over 2 million acres and (iv) several integrated floodplain management scenarios. Extreme flood events are more common in recent decades, and they are expected to continue to occur at greater frequency in response to climate change. Floodplain managers can use the results presented here to help optimize land management and flood damage reduction on the Upper Mississippi River System. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.