The MR&T functional category consists of a variety of infrastructure types, including levees, navigation works, and dams. This functional category is unique in several ways. It is the only functional category whose infrastructure is defined by geography rather than a function or purpose. The MR&T functional category includes 3,727 miles of levees and floodwalls providing flood risk reduction to approximately 4 million people in the Lower Mississippi River Basin (USACE 2009). This levee system is enhanced by more than 1,000 miles of revetment infrastructure that protects the system from erosion. Other MR&T assets include navigation infrastructure such as locks, dams, and dikes. In 2011, MR&T infrastructure prevented an estimated $110 billion in damages to the people and property protected by the MR&T system (Mississippi River Commission 2011).
A revetment is a structure characterized by small concrete blocks joined together by wires placed on the river bank to maintain the proper channel alignment and protect nearby levees from bank erosion (USACE 2009).
Simple observations on the calculated capital stock value covered under the MR&T functional category are as follows (values in 2021 $):
- The greatest investment in this stock occurred from 1928 through 1940 (see ‘USACE Capital Stock Additions, MR&T’ figure). Since then, annual investments in 2021 dollars have been variable, ranging from a high of $1.26 billion in 1950 to a low of $75.7 million in 2020 and averaging $523 million annually.
- The peak USACE MR&T capital stock value occurred in 1978 at $32 billion. Since 1978, annual deterioration in the estimated capital stock has exceeded investments.
- The average rate of decline from 1978 to 2021 is 1.6% annually.
The 2021 USACE MR&T capital stock value is $16.0 billion, or approximately what it was in 1938, and about 48% of its peak 1978 value.