The Morganza Spillway or Morganza Control Structure is a flood-control structure in the U.S. state of Louisiana. It is located along the western bank of the Lower Mississippi River at river mile 280, near Morganza in Pointe Coupee Parish. The spillway stands between the Mississippi and the Morganza Floodway, which leads to the Atchafalaya Basin and the Atchafalaya River in south-central Louisiana. Its purpose is to divert water from the Mississippi River during major flood events by flooding the Atchafalaya Basin, including the Atchafalaya River and the Atchafalaya Swamp. The spillway and adjacent levees also help prevent the Mississippi from changing its present course through the major port cities of Baton Rouge and New Orleans to a new course down the Atchafalaya River to the Gulf of Mexico. The Morganza Spillway, operated by the U.S. Army Corps of Engineers, was opened during the 1973 and 2011 Mississippi River floods. [1] [2] [3] [4] [5]
The Great Mississippi Flood of 1927 was the most destructive river flood in the history of the United States. [6] This was in large part due to the Mississippi River swelling to 80 miles (130 km) wide in spots. [7] To prevent a repeat of the Great Flood of 1927, and to have better control over river flooding in general, Congress passed the Flood Control Act of 1928. This authorized the United States Army Corps of Engineers to build the Bonnet Carre Spillway, [note 1] the Birds Point floodway in Missouri, and the Morganza Floodway as part of the 1928 Mississippi River and Tributaries Project. [7]
Construction of the levees that make up part of the Morganza Spillway began in the late 1930s. The Morganza Control Structure portion of the project was completed in 1954. [7] It subsequently became incorporated into the Mississippi River Commission's 1956 project design flood, [9] which added the Old River Control Structure (ORCS) in 1963 to the protections used to prevent Mississippi River flood. [10] The Flood Control Act of 1965 provided further regulation over the Morganza Spillway's role in Mississippi River flood prevention. A concrete pit called a stilling basin was added at the Morganza Spillway in 1977 "to provide erosion protection after the velocity of water pouring through the open bays during a 1973 flood caused severe scouring of the land behind the bays." [11]
The Morganza Spillway, a 4,159-foot (1,268 m)controlled spillway using a set of flood gates to control the volume of water entering the Morganza Floodway from the Mississippi River, consists of a concrete weir, two sluice gates, seventeen scour indicators, and 125 gated openings which can allow up to 600,000 cubic feet per second (17,000 cubic metres per second ) of water to be diverted from the Mississippi River into the Atchafalaya Basin during major floods. The project was completed in 1954.
A highway (Louisiana Route 1) and the Kansas City Southern Railway cross the structure.
The Corps of Engineers maintains the structures and, in times of flood, monitors their piers for scouring and stability. The Corps of Engineers has two 25-ton cranes used to lift and lower the flood gates. The cranes roll on special tracks next to the roadway, enabling the operators to open or shut any spillway gate or perform maintenance while the roadway is in use.
The land on both sides of the Morganza Control Structure is above normal river water levels, and usually dry. In order for water to reach the spillway, the Mississippi must first rise well above its flood stage, overtopping its banks. The Corps of Engineers considers opening the Morganza Spillway when the flow of the Mississippi at Red River Landing, Louisiana, [12] [13] is greater than 1,500,000 cu ft/s (42,000 m3/s) and rising. [1]
Water from the Mississippi is normally diverted into the Atchafalaya Basin at only one place, the Old River Control Structure (ORCS), in use since 1963, where floodgates are routinely used to redirect the Mississippi's flow into the Atchafalaya River such that the volume of the two rivers is split 70%/30%, respectively, as measured at the latitude of Red River Landing. During the 1973 Mississippi flood, the ORCS was being damaged due to high flow rates, leading to the opening of the Morganza Spillway to help relieve this pressure. Subsequently, the nearby Old River Control Auxiliary Structure (ORCAS) was constructed, adding additional floodgates for use during major floods.
The Morganza Spillway, about 30 miles (48 km) downriver from ORCS and ORCAS, is designed for emergency use to divert additional water from the Mississippi River into the Morganza floodway, which merges downstream with the Atchafalaya floodway before entering the Gulf. Diversion of water from the Mississippi's main channel has the effect of lowering water level in the Mississippi downstream of the spillway, helping to relieve stress on levees and other flood control structures both upstream and down. Besides controlling flooding in a given event, the system is also designed to prevent the Mississippi River from permanently altering course down the Atchafalaya River, bypassing Baton Rouge and New Orleans. [1] [2] [3] [4]
Water that passes the Morganza Spillway first enters the Morganza Floodway, which extends from the spillway at the Mississippi River south to the East Atchafalaya River levee. The floodway, 20 miles (32 km) long and 5 miles (8.0 km) wide, includes a stilling basin, an approach channel, an outlet channel, and two guide levees. [1] From there, diverted water enters the Atchafalaya River Basin Floodway near Krotz Springs, Louisiana, [1] and continues to the Gulf of Mexico.
In an extreme flood event, a major release of water from the Morganza Spillway into the Morganza Floodway and Atchafalaya Basin inundates not only the floodways themselves (between their levees), but extensive additional areas of southern Louisiana throughout the Atchafalaya Basin. In such an event, the water level of the Mississippi, high enough to overtop the Spillway, would already be flooding some areas in the Basin downstream of the spillway, due to increased flow through the ORCS and the ORCAS, as well as possible overtopping of levees near the spillway. [14] This flooding, plus any additional water from a Morganza Spillway release, together determine the total extent of flooding throughout the Atchafalaya Basin during a major Mississippi River flood.
At risk in the Atchafalaya Basin are Morgan City (population 13,500), various smaller populated places, many farms, thousands of oil and gas wells, and considerable swampland. Inhabitants know that the region is a natural floodplain, and the Corps of Engineers issues written notices annually to all interests reminding them of the possibility that it might open the spillway and flood the area. Any decision to open the spillway must be carefully planned to give ample warning and protect life and property. Part of that planning process includes the Corps' preparation of maps known as "inundation scenarios" so that interested parties can discuss how much water, if any, should be allowed through the spillway. [1] [15] [16] [17] [18] [19] [20] [21] [22]
During both moderate and severe floods of the Mississippi, the Bonnet Carré Spillway can also be opened to help protect New Orleans, many parts of which are below sea level. The Bonnet Carré Spillway, built after the Great Mississippi Flood of 1927, is located well downstream of Morganza, where the Mississippi River approaches Lake Pontchartrain near New Orleans. The Corps uses Bonnet Carré to divert floodwaters into the lake in order to protect the levees near New Orleans.
Integrity of the Morganza Spillway, the Old River Control Structure, and nearby levees is essential to prevent the Mississippi from diverting its main channel into the Atchafalaya Basin. [23]
Since its completion in 1954, the Morganza Spillway has been opened twice, in 1973 and 2011. The Morganza Spillway was also considered for opening during other major floods of the Lower Mississippi River.
On April 17, 1973, in order to lower the water level of the Mississippi River and relieve pressure on the Old River Control Structure, the Corps of Engineers opened 42 of the 125 steel gates of the Morganza Spillway for the first time since its completion, allowing about half of its maximum designed flow rate to pass from the Mississippi into the Atchafalaya Basin. The spillway received minor scouring and slight damage to the stilling basin, and substantial flooding occurred in the Atchafalaya Basin. After the 1973 flood, the structure was restored to its original condition. [1] [3] [24] [25]
The issue of opening the gates to keep the Mississippi in its current place was next raised in May 1983. [26] Although the gates were not opened, Louisiana Highway 1 running across the spillway was closed, and the Corps of Engineers built a 12-foot (3.7 m) ring dike and put a blanket of earth across a section of the spillway to contain water pouring underneath it. [27]
During the Great Mississippi and Missouri Rivers Flood in 1993, officials decided to leave the gates of the Morganza Floodway closed. [28]
In March 1997, the river water flow at Baton Rouge reached 10,600,000 US gal (1,420,000 cu ft) (40,000 m3) per second. [29] However, the flow rate never reached the threshold of 11,200,000 US gal (1,500,000 cu ft) (42,000 m3) per second for opening Morganza, [29] and residents of Sicily Island, Louisiana, became angry that the spillway was not opened to prevent flooding in their homes. [30] [31] [32]
In March–April 2008, officials considered but declined to open the spillway gates. [25] [33] [34] While the spillway gates remained closed then, flooding occurred in the Morganza forebay when the Mississippi River crested higher than the potato ridge levee at the forebay entrance. Local residents and National Guard troops attempted to add height to the permanent levee by building a supplemental sandbag levee on top of it. However, additional rainfall raised the flood crest higher than even the supplemental sandbags, sending floodwaters over these levees into 3,000 acres (1,200 ha) of cropland located within the floodway. [14] In the spring of 2016, the Corps considered opening the spillway but the forecast was lowered for the crest of the Mississippi River at Red River Landing, so the gates were left closed.
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The 2011 Mississippi River floods began to become serious in April. In response, the Corps first analyzed the flooding, and then opened the spillway in a controlled manner. The Corps studied four flooding scenarios, all of which assumed the Bonnet Carré Spillway would be concurrently operating at full capacity (100%).
Following this analysis, which showed that extensive flooding was expected in the Atchafalaya Basin regardless of the choice made regarding the Morganza Spillway, the Corps decided to start the 2011 diversion by opening the spillway a bit less than described in scenario 1a (21%, not 25%) [36]
The Governor of Louisiana, Bobby Jindal, had meanwhile sent a letter on May 4, 2011, to Robert Gates, the United States Secretary of Defense, requesting that the National Guard be deployed under Title 32 of the United States Code status to respond to record water levels in Louisiana, where there was "a significant probability that the U.S. Army Corps of Engineers [would] open the Morganza Spillway for the first time since 1973." [37]
The second opening of the Morganza Spillway began with the lifting of a single floodgate on May 14, 2011. Diversion of 125,000 cubic feet per second (3,500 m3/s) of water from the Mississippi River to the Atchafalaya Basin was planned during this event, with the structure operating at about 21% of its capacity. This diversion was deemed necessary to protect levees and prevent major flooding in Baton Rouge and New Orleans, with the tradeoff of creating possibly severe flooding in the Atchafalaya Basin. [1] [38]
By May 18, 2011, a total of 17 gates (the largest number for the 2011 event) had been opened by the Corps of Engineers. The Corps estimated the flow rate at 114,000 cu ft/s (3,200 m3/s). However, on May 25, new estimates from the U.S. Geologic Survey (USGS) described a much higher rate of 172,000 cu ft/s (4,900 m3/s), resulting in the closure of 3 bays by May 26, and additional closures by May 29, bringing the total to 11 bays with an estimated diversion rate of 120,000 cu ft/s (3,400 m3/s). [39] [40] The Corps continued to evaluate the flow and close additional bays as appropriate. By June 6, the number of open gates had been reduced to seven, [41] and by June 8, only two gates were still open. [40] All bays were closed on July 7, 2011.
The Corps had estimated that it would take opening 31 of the Spillway’s 125 bays to control the flow of the river through Baton Rouge in response to a forecast crest of 45 feet (14 m) anticipated on Tuesday, May 17, 2011, which must remain below 1,500,000 cu ft/s (42,000 m3/s) of water per second through Baton Rouge to ensure the integrity of the levee system. [42] Since Morganza never operated above 172,000 cu ft/s (4,900 m3/s), the flooding in the Atchafalaya Basin was considerably lower than had been anticipated during the initial estimates of 300,000 cu ft/s (8,500 m3/s). [39] By May 29, the Corps had also opened 330 of the 350 bays of the Bonnet Carré Spillway located near New Orleans. [40]
On Wednesday May 22, 2019, the U.S. Army Corps of Engineers announced that, due to the extended flood event on the Mississippi River, which had been above flood stage since January 2019, they were anticipating the third opening of the Morganza Spillway. The further anticipated river rise stoked fears that the waters would overtop the spillway, which would destroy the structure. On Monday May 27, 2019, the Army Corps of Engineers officially announced it would open Morganza on Sunday, June 2, 2019. [43]
However, the US Army Corps of Engineers New Orleans issued a press release on May 30, 2019, announcing the postponement of the Spillway opening until June 6, 2019. The opening was later postponed again to June 9, then indefinitely. [44] [45] [46]
The Mississippi River is the primary river, and second-longest river, of the largest drainage basin in the United States. From its traditional source of Lake Itasca in northern Minnesota, it flows generally south for 2,340 miles (3,766 km) to the Mississippi River Delta in the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains all or parts of 32 U.S. states and two Canadian provinces between the Rocky and Appalachian mountains. The main stem is entirely within the United States; the total drainage basin is 1,151,000 sq mi (2,980,000 km2), of which only about one percent is in Canada. The Mississippi ranks as the thirteenth-largest river by discharge in the world. The river either borders or passes through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.
Morganza is an incorporated village near the Mississippi River in Pointe Coupee Parish, Louisiana, United States. The population was 610 at the 2010 census, down from 659 in 2000. As of 2020 the population was 525. It is part of the Baton Rouge metropolitan statistical area. The village's zip code is 70759. The Morganza Spillway, a flood control structure between the Mississippi River and the Atchafalaya Basin, is located nearby.
The Atchafalaya River is a 137-mile-long (220 km) distributary of the Mississippi River and Red River in south central Louisiana in the United States. It flows south, just west of the Mississippi River, and is the fifth largest river in North America, by discharge. The name Atchafalaya comes from Choctaw for 'long river', from hachcha, 'river', and falaya, 'long'.
The Old River Control Structure is a floodgate system in a branch of the Mississippi River in central Louisiana. It regulates the flow of water from the Mississippi into the Atchafalaya River, thereby preventing the Mississippi River from changing course. Completed in 1963, the complex was built by the U.S. Army Corps of Engineers in a side channel of the Mississippi known as "Old River", between the Mississippi's current channel and the Atchafalaya Basin, a former channel of the Mississippi.
The Bonnet Carré Spillway is a flood control operation in the Lower Mississippi Valley. Located in St. Charles Parish, Louisiana, about 12 miles (19 km) west of New Orleans, it allows floodwaters from the Mississippi River to flow into Lake Pontchartrain and thence into the Gulf of Mexico. The spillway was constructed between 1929 and 1931, following the Great Mississippi Flood of 1927, and has been designated as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers.
The Atchafalaya Basin, or Atchafalaya Swamp, is the largest wetland and swamp in the United States. Located in south central Louisiana, it is a combination of wetlands and river delta area where the Atchafalaya River and the Gulf of Mexico converge. The river stretches from near Simmesport in the north through parts of eight parishes to the Morgan City southern area.
Elliot City is a ghost town that was located in Pointe Coupee Parish's 10th Ward, approximately 6 miles west of Livonia, Louisiana United States. The site of the town itself is located at coordinates 30.555942, -91.662475, and is covered or partially covered by the current U.S. Route 190 roadway.
East Krotz Springs is a ghost town that was located in Pointe Coupee Parish's 1st Ward, approximately 12 miles west of Livonia, Louisiana, United States. The site of the town itself is located at coordinates 30°32'12.87"N, 91°44'24.59"W, and is abandoned. United States Geological Survey maps from 1948 show the town to be located on the east bank of the Atchafalaya River at the mouth of Bayou Sherman, directly across from Krotz Springs, south of the railroad bridge.
Butte La Rose is an unincorporated community in St. Martin Parish, Louisiana, United States. In the 21st century, the area is known for its wilderness campgrounds, and the Atchafalaya Welcome Center.
The Atchafalaya National Wildlife Refuge is located about 30 miles (48 km) west of Baton Rouge, Louisiana, and one mile (1.6 km) east of Krotz Springs, Louisiana, lies just east of the Atchafalaya River. In 1988 under the administration of Governor Foster the "Atchafalaya Basin Master Plan" was implemented that combined the 11,780-acre (4,770 ha) Sherburne Wildlife Management Area (WMA), the 15,220-acre (6,160 ha) Atchafalaya National Wildlife Refuge, and the 17,000-acre (6,900 ha) U.S. Army Corps of Engineers' Bayou Des Ourses into the Sherburne Complex Wildlife Management Area.
The Sherburne Complex is a joint land management venture of the U.S. Fish and Wildlife Service, the Louisiana Department of Wildlife and Fisheries (LDWF), and the U.S. Army Corps of Engineers that began in 1983. The area consists of 44,000 acres (180 km2), and is managed by the Louisiana Department of Wildlife and Fisheries. The complex is located in the Morganza Flood way system of the Atchafalaya Basin about 30 miles (48 km) west of Baton Rouge, Louisiana and actually extends a little south of the I-10 Atchafalaya Basin Bridge at Whiskey Bay, Louisiana. The bridge crosses the Whiskey Bay Pilot Channel. Located on the graveled LA 975, the west boundary is on the east side of the Atchafalaya River with the east boundary being the East Protection Levee. The complex stretches just north of old highway 190, and a short distance to the south of I-10. The nearest town is Krotz Springs to the north off US 190.
There are three outfall canals in New Orleans, Louisiana – the 17th Street, Orleans Avenue and London Avenue canals. These canals are a critical element of New Orleans’ flood control system, serving as drainage conduits for much of the city. There are 13 miles (21 km) of levees and floodwalls that line the sides of the canals. The 17th Street Canal is the largest and most important drainage canal and is capable of conveying more water than the Orleans Avenue and London Avenue Canals combined.
Major floods along the Mississippi River in April and May 2011 were among the largest and most damaging recorded along the U.S. waterway in the past century, comparable in extent to the Great Mississippi Flood of 1927 and Great Flood of 1993. In April 2011, two large storm systems deposited record levels of rainfall on the Mississippi River drainage basin. When that additional water combined with the springtime snowmelt, the river and many of its tributaries began to swell to record levels by the beginning of May. Flooding occurred in Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.
The Birds Point-New Madrid Floodway is a flood control component of the Mississippi River and Tributaries Project located on the west bank of the Mississippi River in southeast Missouri just below the confluence of the Ohio and Mississippi Rivers. The construction of the floodway was authorized by the Flood Control Act of 1928 and later modified by the Flood Control Act of 1965. Its purpose is to divert water from the Mississippi River during major flood events and lower the flood stages upstream, notably at Cairo, Illinois.
The Mississippi flood of 1973 occurred between March and May 1973 on the lower Mississippi River. The flooding was the third most severe along the U.S.'s Mississippi River during the 20th century.
The West Atchafalaya Floodway is a flood control structure of the Mississippi River and Tributaries Project located in the Lower Atchafalaya Basin in south-central Louisiana. It has a project design flood flow capacity of 250,000 cu ft/s (7,100 m3/s).
Flooding in the Mississippi River Basin during the winter, spring, and summer of 2019 caused at least 12 deaths and economic losses in 19 states totaling in excess of $20 billion. Estimated damages in the Midwestern United States alone had reached $12.5 billion by April 2019. Flood damages totaling $6.2 billion were reported in the 11 states bordering the Mississippi River. In addition to property and crop losses and infrastructure damages, commercial navigation on the Mississippi River was interrupted repeatedly by high currents, low bridge clearances, and closed locks. This delayed shipments of agricultural commodities, adding to the economic stress of crop losses caused by flooding. As of late April 2019, shipments of corn to export terminals in Louisiana were 31% lower than in same period in 2018.
Red Cross is a ghost town that was located in Pointe Coupee Parish's 1st Ward, approximately 12 miles west of Morganza, Louisiana, United States. The site of the town itself is located at coordinates 30°32'12.87"N, 91°44'24.59"W, at the intersection of the southern terminus of Louisiana Highway 417 and Louisiana Highway 10. The town is now abandoned. United States Geological Survey maps from 1948 show the town to be located on the east bank of the Atchafalaya River, directly across from Melville, Louisiana, slightly north of the railroad bridge.