Flood trends and river engineering on the Mississippi River system

Along >4000 km of the Mississippi River system, we document that climate, land‐use change, and river engineering have contributed to statistically significant increases in flooding over the past 100–150 years. Trends were tested using a database of >8 million hydrological measurements. A geospatial database of historical engineering construction was used to quantify the response of flood levels to each unit of engineering infrastructure. Significant climate‐ and/or land use‐driven increases in flow were detected, but the largest and most pervasive contributors to increased flooding on the Mississippi River system were wing dikes and related navigational structures, followed by progressive levee construction. In the area of the 2008 Upper Mississippi flood, for example, about 2 m of the flood crest is linked to navigational and flood‐control engineering. Systemwide, large increases in flood levels were documented at locations and at times of wing‐dike and levee construction.