Alcances del liderazgo transformacional comparado con el liderazgo instruccional

On May 2, the major fl ood bearing down on the Vicksburg Engineer District was about to become worse. During the Lower-Ohio Mississippi River coordination teleconference that day, the National Weather Service formally delivered its revised forecast for the Cairo gage. “Sixty-three feet,” Robert Simrall said aloud in amazement. Henry Dulaney, the relatively new chief of engineering and construction at the Vicksburg district became alarmed by Simrall’s reaction. The obscure number on a distant gage did not register with Dulaney – who had a background in design and technical services – as it had with Simrall and the other members of the water control team present. He looked at Simrall and asked, “What does 63 mean?” Simrall replied, “It means our whole world is fi xing to change!”¹⁸⁶

As the teleconference continued, the magnitude of the fl ood in the midsection of the MR&T project began to crystallize. The heavy rains had not only worsened fl ood conditions at the confl uence of the Mis-sissippi and Ohio rivers, but they also wreaked additional havoc in the already swollen Arkansas and White basins. Three of the fi ve major reservoirs comprising the White river system – Beaver, Table Rock, and Norfolk lakes – went to emergency spillway operations. The two other major reservoirs – Greer’s Ferry Lake and Bull Shoals Lake –did not require spillway discharges, but experienced extremely high pool elevations, nonetheless. The Arkansas River also experienced signifi cant fl ooding. The rain fell where the eleven major fl ood control reservoirs in the Arkansas system could not be of use, but the Southwest Division deviated from its water control plans and reduced discharges from the dams to reduce fl ows downstream. By May 6, water control managers from the Southwest Division anticipated the combined fl ows entering the Mississippi River from the Arkansas and White rivers to approach

500,000 cfs, just days before the crest rolling down the Mississippi River arrived. All of this translated into a stunning forecast for the major gages in the Vicksburg Engineer District: Arkansas City 53.5 feet, Greenville 64.5 feet, Vicksburg 57.5 feet, and Natchez 64 feet – a range of 14.5 feet to 16.5 feet above fl ood stage on each gage.¹⁸⁷

While the mainline levees in the system stood high enough to hold back the river without overtopping – with the exception of signifi cant low spots spanning nearly 3,000 feet near Vidalia, Louisiana – the levees would soon be facing a level of pressure never before experienced. At Greenville, the predicted crest stage would fall about one foot shy of the record stage reached in 1927, but it would break the 1973 stage by more than six feet. At Vicksburg, the new forecasted stage would top them all – more than one foot higher than 1927, more than four feet higher than 1937, and more than six feet higher than 1973. The thought of a fl ood six feet greater than 1973 fl ood stages at Greenville

and Vicksburg sent a shiver of fear through most of the people living in the Mississippi delta. Those people could not relate to the fl oods of 1927 and 1937 because the events had taken place 84 years and 74 years ago, respectively. The same could not be said of the 1973 fl ood. The majority of delta residents 40 years of age or older vividly recalled the devastation of that fl ood, when nearly one million square-miles of land were inundated in the Yazoo basin alone. While areas in Arkan-sas and Louisiana, particularly those in the Ouachita basin, suffered extreme hardships during the 1973 fl ood, approximately 45 percent of the land fl ooded during the event was in Mississippi. The Yazoo basin, particularly the area known as the Yazoo backwater area, served as the epicenter of devastation in Mississippi.¹⁸⁸

Backwater areas are the necessary result of gaps left in the Missis-sippi River levee system at the mouths of major tributaries that empty into the river. Prior to the construction of the levee system, the backwater areas were no different than most lands comprising the alluvial valley.

They fl ooded when the Mississippi River overfl owed its natural alluvial banks or backed into the tributary streams. As the levee system gradu-ally extended upriver, the confi nement of Mississippi River fl oodwaters protected lands upriver from the backwater areas from overbank fl ows, but fl oods continued to back up through the gaps and around the lower end of the levees, inundating the low-lying areas behind the levees. As originally authorized in 1928, the MR&T project did not contemplate protection of the major backwater areas in the lower Mississippi valley at the mouths of the St. Francis, White, Yazoo, and Red rivers. Histori-cally, the Mississippi River Commission recognized the importance of maintaining the natural storage capacities of the backwater areas as a benefi t for fl ood control. The low-lying lands stored vast quantities of fl oodwaters, thereby lowering fl ood stages on the river by reducing the peak fl ows downstream of the backwater areas. After the initial success of Maj. Gen. Harley Ferguson’s channel realignment and rectifi cation program carried out in the 1930s, which improved the ability of the

river to carry more water at lower stages, calls for improving conditions in the backwater areas gained momentum. The call was particularly strong in the Yazoo basin, where several reservoirs and other improve-ments had been authorized through the 1936 Overton Act to provide protection from headwater fl oods emanating from the hill country in the upper part of the basin. All that remained for the basin to maximize the benefi ts achieved through the enhanced mainline levees, the improved carrying capacity of the Mississippi River channel, and the protection from headwater fl ooding was protection from backwater fl ooding at the lower end of the basin.

While maintaining the position that the backwater area could never be fully redeemed from fl ooding, the Mississippi River Commission eventually conceded that the Yazoo basin could receive substantial pro-tection from fl oods, provided the improvements did not hamper the natu-ral reservoir effect the area provided during larger fl oods approaching project design fl ood elevations. The 1941 Flood Control Act authorized a plan developed by the Mississippi River Commission to provide for a level protection – corresponding to a height of 56.5 feet on the Vicksburg gage – for roughly 634,000 acres in the Yazoo backwater. The commis-sion’s plan involved the construction of a backwater levee extending from the existing Mississippi River mainline levee along the west bank of the Yazoo River to Yazoo City, where the levee would connect with the levee authorized under the 1936 Overton Act to control headwater fl oods. Recognizing that the backwater levee would impound runoff from the tributaries that traversed the backwater area and emptied into the Yazoo River, the commission recommended constructing a drainage structure at the Little Sunfl ower River and a combination of structures and pumping plants at the mouths of the Big Sunfl ower River, Deer Creek, and Steele Bayou to evacuate impounded water. When stages on the Mississippi and Yazoo rivers were too high to allow for grav-ity drainage, the plan made provisions for pumping stations at three

locations with a total discharge capacity of 14,000 cfs – Big Sunfl ower River (11,000 cfs), Deer Creek (700 cfs) and Steele Bayou (2,300 cfs).¹⁸⁹

Following a comprehensive review of the MR&T project in 1959, the Mississippi River Commission recommended changes to the plan after noting that channel improvements in the Mississippi River and reservoirs and associated works in the upper basin had reduced the fre-quency and duration of fl ooding in the backwater area. The plan called for replacing the previously-authorized pumping stations at the Big Sunfl ower River, Deer Creek, and Steele Bayou with improved grav-ity drainage structures and a 20-mile long and 200-foot wide channel connecting the Sunfl ower River and Steel Bayou ponding areas to the outlets at the Little Sunfl ower and Steele Bayou fl oodgates. The 1965 Flood Control Act authorized the proposed modifi cations and contion of the project quickened. In 1969 the Steele Bayou drainage struc-ture, designed to discharge 19,000 cfs from the ponding area into the Yazoo River, was completed. In 1975, the drainage structure at Little

Sunfl ower River capable of discharging 8,000 cfs was completed.¹⁹⁰ In between the dates of completion for the two drainage structures, the 1973 fl ood struck the lower Mississippi Valley. The backwater levee had yet to be constructed, leaving the lower end of the Yazoo basin exposed. In early April 1973, the swollen Yazoo River overtopped a natural ridge along Deer Creek and began fi lling the Steele Bayou ponding area. A week later, the river and backwater levels equalized at an elevation of 99 feet, creating a lake 60 miles long and 40 miles wide. But the water levels continued to rise, cresting another two and a half feet higher on May 15. The backwater continued to creep farther north into the Yazoo basin until more than 1,000 square miles lay under water. It took several more weeks for the water to drain out. Thousands of people, many of them farmers, returned to fi nd their homes and property destroyed.¹⁹¹

The May 2, 2011, forecast of 57.5 feet on the Vicksburg gage cer-tainly caught the attention of the district’s water control engineers. Most

engineering analyses and model tests dating back to the 1950s indicated that the Yazoo backwater levee would overtop as designed when the Mississippi River approached a range of 56.2 to 56.6 feet on the Vicks-burg gage. The information on channel conditions used in development of the studies, though, was several decades old. The 2008 fl ood afforded the Vicksburg Engineer District the opportunity to gather fresh informa-tion. The river reached 57.3 feet on the Greenville gage and 51 feet on the Vicksburg gage in 2008. Both stages were less than one foot lower than stages experienced on both gages during the 1973 fl ood. Ronald Goldman, the district’s chief of hydraulic engineering, used the fl ood as an opportunity to gain more knowledge of the river. As the peak fl ow moved downstream through the district, contract crews in a survey boat measured the depth of the centerline of the channel, while additional crew members at the exact latitude on the levees on both sides of the river plotted the exact high water mark. They repeated the process every half mile. Hydraulic engineers used the data to develop a modern or updated profi le of the river in terms of its slope and the relationship between stage and discharge. From this profi le, the Vicksburg district developed a new baseline to more accurately determine how the river would respond under existing channel conditions. The 2008 profi le con-fi rmed what previous studies had shown – the Yazoo backwater levee would overtop when the river reached 56.3 feet on the Vicksburg gage.

With an anticipated crest stage of 57.5 feet on the Vicksburg gage, the backwater levee would overtop by more than one foot.¹⁹²

At the Mississippi Levee Board offi ce, Peter Nimrod could not believe what his ears were hearing. “What? No way!” Kent Parrish had called to inform him that the Vicksburg district’s hydraulic engi-neers expected the 28-mile backwater levee to overtop by more than a foot for at least ten days. The overtopping itself did not concern him.

It would certainly create some hardship in the lower Yazoo basin, but he believed that the levee board could manage the additional water.

backwater levee; to raise the levee with sandbags and HESCO bas-tions – large containers fi lled with sand. No, the overtopping was not Nimrod’s main concern. The prospect of losing the backwater levee entirely, though, terrifi ed him.

Ten days! Nimrod thought to himself. Ten days! The hydraulic engi-neers at the Vicksburg district expected more than a foot of water to fl ow over the top of the 28-mile long backwater levee for ten days. It was disconcerting enough for him to know that the water on the river side of the levee would be approximately 17 feet higher than the ground on the landside. The highest differential the levee had ever experienced in the past was a little more than nine feet in 2008. The immense pressure on the levee from the head differential alone was extremely worrisome, but the added powerful and constant force of more than a foot of water eroding the crown, the landside slope, and the toe of the levee for ten consecutive days frightened Nimrod. The backwater levee was a fi ne and well-constructed levee, but under those conditions, ten days rep-resented a lifetime. Nimrod started doing the calculations in head. If the levee failed, the south Mississippi delta faced a catastrophe. Water levels in the backwater area would be six feet higher than those expe-rienced during the 1973 fl ood. Rolling Fork and Mayersville, both of which stayed high and dry during the 1973 fl ood, would be inundated.

Nimrod pictured a map of the backwater levee in his mind. Twenty eight miles of levee overtopping for ten days! The levee had to hold.¹⁹³

On May 3, Goldman, Simrall, and Wayland Hill began poring over profi les and data in more detail. Residents in the backwater area were about to catch their fi rst break. The 2008 profi le that Goldman had com-missioned showed a steeper slope in the Yazoo River than originally thought – as much as a half a foot steeper. Using information collected during the 2008 fl ood, the district’s hydraulic engineers determined that if the river reached 57.5 feet on the Vicksburg gage, the backwa-ter levee would only overtop along a four-mile stretch extending from the junction of the Mississippi River mainline levee and the Yazoo