Flood Control Levees Research Articles

Floodplain restoration with flood control: Fish habitat value of levee borrow pits

Earthen flood control levees are often built using soil excavated from borrow pits lying parallel to and riverward of the finished levee. After construction, these pits can provide valuable floodplain habitats, and their value along corridors of larger rivers is well established. However, levee borrow pits along smaller streams have not been studied. Six waterside levee borrow pits were studied for about three years along Abiaca Creek, which drains a 202km2 watershed in central Mississippi. Fish were sampled annually from six pits using boat-mounted electrofishing, and water quality samples were collected weekly from four pits. Continuous records of stream and borrow pit water levels were coupled with topographic and bathymetric survey data of the floodway to compute the frequency of connection between each pit and temporal distributions of aquatic habitat characteristics. Pit water surface areas ranged from 0.4 to 11.7ha, and mean depth ranged from 0.5 to 1.8m. Pits were hydraulically connected to the stream 1–34% of the time. Dissolved oxygen concentrations ranged from 0.30 to 13.7mg/L and were inversely related to water depth. Fish collections yielded 1768 individuals representing 26 species. Larger-bodied fishes and some piscivores were more common in larger, more elongated pits with more sinuous shorelines and lower turbidity. Setback levees with waterside borrow pits are a viable stream corridor restoration concept for smaller streams as well as major rivers.

Impacts of Mississippi River diversions on salinity gradients in a deltaic Louisiana estuary: Ecological and management implications

Large-scale river diversions on the lower Mississippi River are considered to be an important component of wetland restoration efforts in coastal Louisiana. Diversions are used primarily for salinity control but increasingly proposed also as a major way to deliver sediments and nutrients to coastal wetlands impacted by the construction of flood control levees. We used a coupled hydrology–hydrodynamics model of the Barataria estuary, a site of the Davis Pond Diversion – the world's largest river diversion project, to examine salinity variations under different diversion discharge scenarios. Discharge scenarios were selected based on actual freshwater discharges in different years and management alternatives that included a scenario with several new diversions. The model results indicate that river diversions strongly affect salinities only in the middle section of the Barataria estuary. The upper parts of the estuary are fresh most of the time and so the excess fresh water from river diversions has only a minor impact on salinity in this region. Also, the Davis Pond diversion has little impact on salinities in the coastal section of the estuary because of strong marine influence in this area adjacent to the Gulf of Mexico. Interestingly, the predicted salinity differences between different model scenarios can be as high as 10 in some months and places. These differences can be biologically significant depending on the salinity tolerance of different species and could cause a shift in community composition within the affected region.

Hurricanes, Floods, Levees, and Nutria: Vegetation Responses to Interacting Disturbance and Fertility Regimes with Implications for Coastal Wetland Restoration

A primary cause of wetland loss in the Louisiana coastal zone has been the construction of flood control levees along the Mississippi River. These levees restrict the inputs of freshwater, nutrients, and sediment that historically replenished these wetlands. Wetland loss is compounded by other factors such as storms, introduced herbivores, and saltwater intrusion. How do such simultaneous changes in fertility and disturbance regimes affect the vegetation of coastal wetlands? Will proposed restoration strategies, such as freshwater diversions and protection from herbivores, increase the productivity and accretion rates of coastal wetlands without sacrificing plant species diversity? During this 2-year study, we applied five disturbance treatments (control, fire, herbivory, single vegetation removal, and double vegetation removal) and four fertility treatments (control, sediment addition, fertilizer addition, and sediment fertilizer addition), using a split-plot factorial design with herbivory exclosures as main plots and species richness and total aboveground biomass as dependent variables. We found that nutria, the principal vertebrate herbivore of the marsh, limited biomass production. Other disturbances decreased biomass, but only to a limited extent in the absence of herbivores. The sediment fertilizer treatment, which simulated the additional nutrients and substrate material that a freshwater diversion might deliver, significantly increased biomass production. Fertilizer significantly increased the biomass only in the absence of herbivores. We had limited success in predicting species richness after 2 years. Only the most severe disturbance decreased species richness, whereas fertilizer addition seemed to have a minor effect (p = 0.08). Sediment- and nutrient-rich waters from freshwater diversions will likely mitigate negative impacts of nutria grazing on biomass and have no effect on species richness. However, it should be noted that freshwater diversions will have the most impact if nutria populations are reduced.

Catastrophic Harm in United States Law: Liability and Insurance

Catastrophes or disasters may be defined as natural or man-made events of significant magnitude causing disruption such that survivors feel deprived of normal social help. In American law, catastrophic harm includes the mass of individual losses suffered by individuals, businesses, and entities of all kind, also including environmental harm. The Federal Emergency Management Agency (FEMA), created in 1979, coordinates the response to disasters occurring in the United States while it administers prevention and organizes relief efforts. However, the system does not work top-down, since local and state governments bear the initial responsibility as first respondents. Local or state failure can cause the system not to be reactive enough, explaining the slow response after Hurricane Katrina. Non-desirable risks tend to concentrate in earthquake, flood, or hurricane prone areas, making such risks uninsurable. Significant efforts are made at state and federal level to make catastrophic risk insurable, pooling risks and sometimes creating compensation funds, especially in the case of nuclear and terrorist risks. Rather than disrupting the market, state or federal intervention tend to create proper conditions for a market to exist where none could otherwise prosper, whilst in best cases encouraging disaster mitigation. Given the weakness of the American welfare system by comparison to other developed countries, victims are more prone than elsewhere to look for a tortfeasor and sue. The jury system, the practice of contingent fee and the availability of class actions make American tort law a powerful pro-plaintiff system and tort law has a large impact wherever defendants can be identified. Insured victims tempted to sue are rarely overcompensated. Sophisticated solutions have been devised for the assessment of environmental damage when caused by oil pollution. Sovereign immunity may bar mass tort litigation against the federal government, for instance, for the failed flood control levees in New Orleans, but history proves that the Corps of Engineers made good proposals but had to comply with wrong political decisions.

Research and Solutions: Sustainable Urban Governance: Lessons from Katrina and the Lean Six Sigma

Discussions about sustainability are often confined to the subject of natural resources, such as water and fossil fuels, and how to preserve them for the future. This is too limited, particularly in the case of cities, which depend on other resources for their existence. These resources include man-made public assets, defined by this author as flood control levees, roads, water supply and sewerage systems, bridges, roads, other urban infrastructure, and monetary wealth. A major threat to the sustainability of cities is the decline of public assets and the inability of governments to maintain them for generations to come. A case in point is the broken levees in New Orleans after Hurricane Katrina. Other examples from around the world demonstrate that such failures of infrastructure and government are epidemic. These problems cannot be solved by merely applying green technology. This article proposes a system of sustainable urban governance, based on the concepts of Lean Six Sigma, a structured problem-solv...

The impacts of re-introducing Mississippi River water on the hydrologic budget and nutrient inputs of a deltaic estuary

Most wetlands of the Mississippi deltaic plain are isolated from riverine input due to flood control levees along the Mississippi River. These levees have altered hydrology and ecology and are a primary cause of massive wetland loss in the delta. River water is being re-introduced into coastal basins as part of a large-scale ecological engineering effort to restore the delta. We quantified freshwater, nitrogen, and phosphorus inputs to the Breton Sound Estuary for three climatically different years (2000, 2001, and 2002). Water budgets included precipitation, potential evapotranspiration, the diversion, stormwater pumps, and groundwater. Precipitation contributed 48–57% of freshwater input, while the diversion accounted for 33–48%. Net groundwater input accounted for less than 0.05% of freshwater inputs. Inputs of ammonium (NH 4-N), nitrate (NO 3-N), total nitrogen (TN), and total phosphorus (TP) were determined for each of the water sources. Atmospheric deposition was the most important input of NH 4-N (57–62% or 1.44 × 10 5–2.32 × 10 5 kg yr −1) followed by the diversion. The diversion was the greatest source of NO 3-N (67–83%, 7.78 × 10 5–1.64 × 10 6 kg yr −1) and TN (60–71%). The diversion contributed 41–60% of TP input (1.17 × 10 5–2.32 × 10 5 kg yr −1). Annual loading rates of NH 4-N and NO 3-N were 0.17–0.27 and 1.2–2.3 g N m −2 yr −1, respectively, for the total basin indicating strong retention of nitrogen in the basin. Nitrogen retention through denitrification and burial was estimated for the upper basin.

Landscape configuration and flood frequency influence invasive shrubs in floodplain forests of the Wisconsin River (USA)

Summary 1. Invasive species are present worldwide, yet predicting which invasive species will become problematic in which ecosystems remains an important ecological challenge. Floodplains are at particular risk for invasion, especially when subjected to anthropogenic disturbance. 2. We examined how components of flood regime, habitat quality and habitat configuration influenced the presence and abundance of three invasive shrubs in the floodplain of the Wisconsin River. Shrub taxa included two non-natives ( Lonicera spp. and Rhamnus spp.) and one native ( Zanthoxylum americanum ). Observations of taxa presence and abundance were recorded in nine forested river reaches, spanning three physiographic regions. We also compared the productivity of Z. americanum across a flood control levee in one reach. 3. Physiographic region significantly predicted the presence and abundance of these three taxa, acting as a synthetic indicator of differences in climate, geography and topography. Invasion was greatest in regions where modifications to flood regime and land use were most pronounced. Physiographic region was excluded from subsequent analyses to assess more specific predictors of shrub distributions. 4. Habitat configuration and quality both predicted shrub taxa presence and abundance. Shrub taxa were most frequently observed and most abundant in small forest patches, near roads, and in sandy soil with low nutrient content. Edge habitats have many of these characteristics. Edges appear to be favoured by avian shrub dispersers and provide conditions suitable for invasive establishment. 5. Flooding influenced non-native and native invaders differently. Non-native taxa were observed less frequently and at lower abundances in frequently flooded areas, probably because of a sensitivity to flooding. However, the presence, abundance and productivity of the native invader increased with flooding. Anthropogenic modifications to the flood regime limited hydrologic connectivity and may have reduced the competitive advantage of flood-tolerant traits, which allowed the invasion of upland species. 6. Synthesis . In the floodplain of the Wisconsin River, anthropogenic modifications that created edge habitat and altered flood regime facilitated shrub invasions, whereas unfragmented forest and intact flood regime limited invasion. Large patches of floodplain forest, less regulated flooding regimes, and lower road densities may help reduce the spread of invasive shrubs in temperate

Riparian vegetation dynamics and evapotranspiration in the riparian corridor in the delta of the Colorado River, Mexico

Like other great desert rivers, the Colorado River in the United States and Mexico is highly regulated to provide water for human use. No water is officially allotted to support the natural ecosystems in the delta of the river in Mexico. However, precipitation is inherently variable in this watershed, and from 1981–2004, 15% of the mean annual flow of the Lower Colorado River has entered the riparian corridor below the last diversion point for water in Mexico. These flows include flood releases from US dams and much smaller administrative spills released back to the river from irrigators in the US and Mexico. These flows have germinated new cohorts of native cottonwood and willow trees and have established an active aquatic ecosystem in the riparian corridor in Mexico. We used ground and remote-sensing methods to determine the composition and fractional cover of the vegetation in the riparian corridor, its annual water consumption, and the sources of water that support the ecosystem. The study covered the period 2000–2004, a flood year followed by 4 dry years. The riparian corridor occupies 30,000 ha between flood control levees in Mexico. Annual evapotranspiration (ET), estimated by Moderate Resolution Imaging Spectrometer (MODIS) satellite imagery calibrated against moisture flux tower data, was about 1.1 m yr −1 and was fairly constant throughout the study period despite a paucity of surface flows 2001–2004. Total ET averaged 3.4×10 8 m 3 yr −1, about 15% of Colorado River water entering Mexico from the US Surface flows could have played only a small part in supporting these high ET losses. We conclude that the riparian ET is supported mainly by the shallow regional aquifer, derived from agricultural return flows, that approaches the surface in the riparian zone. Nevertheless, surface flows are important in germinating cohorts of native trees, in washing salts from the soil and aquifer, and in providing aquatic habitat, thereby enriching the habitat value of the riparian corridor for birds and other wildlife. Conservation and water management strategies to enhance the delta habitats are discussed in light of the findings.

Rapid Economic Assessment of Flood-control Failure along the Rio Grande: A Case Study

Recent flood events along the international border between the USA and Mexico resulted in significant economic damage and loss of human life. The International Boundary and Water Commission, the agency responsible for monitoring US–Mexican flood control levees, had requested funding for maintenance and improvement of these levees. However, the Office of Management and Budget requires agencies to provide benefits or in this case avoided loss estimates to justify the budget request. Due to severe time constraints in the budgetary process there was a need for a rapid assessment of the potential economic impacts from a failure of this ageing flood-control infrastructure. The economic losses avoided by four major flood-control projects on the Rio Grande were estimated using an innovative combination of satellite imagery, geographic information systems, and economic methods. The control projects apply to about 547 km (340 miles) of levees from Caballo Reservoir in New Mexico to Brownsville, Texas, and include several million people, extensive industry, and agricultural production. High resolution imagery was used to identify and quantify potential flood inundation areas, types of land use, and impacts of flood-control infrastructure failure. Value estimates of residential, industrial, and commercial property, and agricultural production at risk were developed from property assessment data, crop enterprise budgets, census data, and community leaders. Damage factors accounting for flood inundation levels and building contents were then used to develop gross economic losses avoided by flood-control infrastructure for each of the different property and land use types in each project area. The baseline analysis indicates that the four projects cumulatively prevent one time losses of US$322.9 million in flood-control protection.

Implications of global climatic change and energy cost and availability for the restoration of the Mississippi delta

Over the past several thousand years, inputs from the Mississippi River formed the Mississippi delta, an area of about 25,000 km 2. Over the past century, however, there has been a high loss of coastal wetlands of about 4800 km 2. The main causes of this loss are the near complete isolation of the river from the delta, mostly due to the construction of flood control levees, and pervasive hydrological disruption of the deltaic plain. There is presently a large-scale State-Federal program to restore the delta that includes construction of water control structures in the flood control levees to divert river water into deteriorating wetlands and pumping of dredged sediment, often for long distances, for marsh creation. Global climate change and decreasing availability and increasing cost of energy are likely to have important implications for delta restoration. Coastal restoration efforts will have to be more intensive to offset the impacts of climate change including accelerated sea level rise and changes in precipitation patterns. Future coastal restoration efforts should also focus on less energy-intensive, ecologically engineered management techniques that use the energies of nature as much as possible. Diversions may be as important for controlling salinity as for providing sediments and nutrients for restoring coastal wetlands. Energy-intensive pumping-dredged sediments for coastal restoration will likely become much more expensive in the future.

CONSEQUENCES OF HUMAN-ALTERED FLOODS: LEVEES, FLOODS, AND FLOODPLAIN FORESTS ALONG THE WISCONSIN RIVER

Flood-control levees are generally thought to increase flood height and velocity for a given discharge. While extensive areas of floodplain in the United States are leveed, the ecological impacts of levees have largely been ignored relative to other anthropogenic impacts to large river floodplains. We examined a century of flood control along the Wisconsin River by comparing simulated flood regimes under “levee” and “levee-removal” scenarios. We also used field sampling to determine if levees had altered the distribution of dominant floodplain forest trees. Increases in flood stage (height) due to levees were minor, only a few centimeters. This was primarily due to the location of the levees, set back hundreds of meters into the floodplain in some areas. Increases in overbank flood velocities due to levees were minimal compared to increases caused by channel constriction and by increased flood magnitude. Generally, levees had a greater impact on stage and overbank flood velocities of larger magnitude events. The mean number of floods and number of days flooded were lower in areas outside (on upland sides) of levees, and stream power was zero in these areas due to a lack of any inundation. These areas also had lower importance values (IV) for several flood-tolerant tree species (Acer saccharinum and Fraxinus pennsylvanica) and higher IVs for some flood-intolerant species (Quercus velutina and Q. ellipsoidalis). Furthermore, areas inside levees (between the levee and the channel) were no different from completely unleveed areas in the number of floods, number of days flooded and in IVs of several dominant tree species. The levee location (set back into the floodplain) resulted in a similar historic flood regime, and thus, similar abundances of floodplain tree species in areas inside levees as compared to completely unleveed areas. Setback levees can provide an important compromise by maintaining the relative abundance of tree species normally found in unleveed areas, while also allowing some flood control. Floodplain restoration involving levee removal should generally target the removal of mainline levees (those adjacent to the channel) rather than removal of setback levees.

Knowledge-based System for Environmental Design of Stream Modifications

A knowledge-based, microcomputer software package was developed for preliminary selection of environmental features for use with streambank protection projects, straightened and enlarged channels, and flood control levees. The system contains a module for each of the three major alteration types: bank protection, levees, and channels. Each module queries the user for information regarding environmental factors to be protected and a description of the project setting, with the internal logic configured to minimize the number of questions asked. System output consists of a list of environmental design features suitable for the specific location and descriptive information. Help screens explain why certain questions are asked, define terms, and suggest responses or sources of information. At the conclusion of a consultation, additional help screens may be displayed that provide a discussion of each recommended feature, a list of existing projects that incorporate the feature, and a bibliography. The streambank protection module screens a master list of 20 methods based on the dominant erosion mechanisms operative at the project site, and the channel module performs a rough channel stability assessment using regime equations.

Female Turkey Habitat Use in Mississippi River Batture

We determined habitat use by adult eastern wild turkey females (Meleagris gallopavo silvestris) in the Mississippi River batture before and after selective thinning of riverfront hardwoods. Thinning reduced basal area from 20.3 to 13.7 m2/ha and decreased canopy closure from 60 to 49%. Midstory density was reduced from 1,421 to 971 stems/ha. One year after treatment mean understory cover increased from 31 to 57%. No nesting occurred because the study area was flooded both springs. Female turkey habitat use changed after thinning; the thinned area received the highest frequency of increased use. An increase in understory cover and hypothesized increase in productivity, particularly of wild turkey food items, apparently were the major attractions for the thinned area. J. WILDL. MANAGE. 52(2):253-260 Some of the largest populations of eastern wild turkeys occurred in the bottomland hardwoods along the Mississippi River (Dickson et al. 1978). This habitat was greatly reduced by extensive conversion to cropland. By 1977, only 20% of the original forest of the lower Mississippi delta remained (U.S. Fish and Wildl. Serv. 1978). Currently, wild turkeys of the Mississippi delta are most abundant in the batture (Hopkins et al. 1980), the land between the river and the flood control levee. Although relatively narrow, the batture along the lower third of the Mississippi River contains approximately 630,000 ha (Lower Mississippi Reg. Comprehensive Stud. Comm. 1974), most of which has not been converted to agricultural production because of seasonal flooding (Frey and Dill 1971). Timber management practices are the primary means for manipulating turkey habitat (Smith 1981). Little information is available on the effects of various forest harvesting methods on habitat use by wild turkeys (Hurst 1981) and immediate effects of a selective thinning (Smith 1986) on wild turkeys in the batture have not been studied. We investigated habitat use by wild turkey females before and after selective thinning of hardwoods in the Mississippi River batture of northeastern Louisiana. Funding for this study was provided by the National Wild Turkey Federation and the Louisiana Department of Wildlife and Fisheries through Louisiana State University. Research was conducted under the auspices of the Louisiana Cooperative Fish and Wildlife Research Unit; U.S. Fish and Wildlife Service, Louisiana State University, Louisiana Department of Wildlife and Fisheries, and Wildlife Management Institute, cooperating. Access to the study area was granted by International Paper Company and Anderson-Tully Company. This is Contribution 87-22-1310, Louisiana Agricultural Experiment Station.

Echanization of concreting the slope revetment slabs of the Leningrad flood-control levees

Echanization of concreting the slope revetment slabs of the Leningrad flood-control levees

Spring mudflows at Wrightwood, Southern California

Summary The Wrightwood area in the San Gabriel Mountains of southern California is known as a site of recurring mudflow activity. The community of Wrightwood is built on the coalesced fans of Sheep, Acorn and Heath Creeks, and the fan deposits are probably chiefly of mudflow origin. Historically, mudflows there have been observed in association with three climatic conditions: (1) short period of high-intensity rainfall during the summer dry season (thunderstorms); (2) periods of heavy rainfall during the October-March winter season, when most of the year's rain and snow fall; and (3) thaw of the winter snow pack. The mudflow activity associated with heavy rainfall has generally been of only a few hours or at most a few days duration. Mudflow activity associated with spring thaw has been of longer duration, as much as several weeks. At various times in the past, mudflows generated by all three conditions have inundated homes and highways in the Wrightwood area, which is now defended by a flood control levee system. During May and June, 1969 the rapid melting of a heavy snow pack resulted in a 40-day period of mudflow activity in Heath Creek. All flows originated in the steep upper reaches of Heath Creek, where steep ravines are incised in the toe of a large active landslide. Direct observation by the authors showed that flows formed when small masses of debris fell or slid from the surface of the landslide mass into the steep channel. Some of the masses were fluid enough to continue downstream without interruption; others stopped in the channel until remobilized by added melt water or the passage of a mudflow from a higher altitude. Both processes resulted in discrete ‘slugs’ which continued down the steep ravine, through an allu-viated canyon, to a fan where most of the debris was deposited. The activity may be described as a spring mudflow cycle, within which three stages were observed in a gradational sequence. A waxing stage began with sporadic short-duration mudflows, during which the lower alluviated canyon floor of Heath Creek was aggraded. A climactic stage of larger mudflows at more frequent intervals and of longer duration was characterized by the incision of a single, narrow, U-shaped channel in the alluviated canyon floor, and transportation of debris as much as 2 miles (3.2 km) from the source. A waning stage followed as meltwater supply decreased; short-duration flows backfilled the U-shaped channel and spilled over the banks, again aggrading the alluviated canyon floor.