Flood Detention Research Articles

Heavy metal concentrations during storm events in a rehabilitated industrialized catchment

AbstractWater quality data collected on a fortnightly or monthly basis are inadequate for assessment and modelling of many water quality problems as storm event samples are underrepresented or missed. This paper examines the stormflow dynamics of heavy metals (Pb, Cu, Cd and Zn) in the Nant‐y‐Fendrod stream, South Wales, which has been affected by 250 years of metal smelting, followed by 35 years of landscape rehabilitation measures. For storm events of contrasting (very dry and very wet) antecedent conditions in May 2000 and February 2001, respectively, temporal changes in streamwater heavy metal concentrations above and below an in‐line flood detention lake are analysed. At the upstream site, peaks in total metal concentration were recorded on the rising limb for Pb (0·150 mg l−1) and Cu (0·038 mg l−1) but on the falling limb for Zn (1·660 mg l−1) and Cd (0·006 mg l−1) in the summer 2000 storm event, yielding clockwise and anticlockwise hysteretic loops respectively. In contrast, metal concentrations, although high throughout the winter storm event, were diluted somewhat during the storm peak itself. The Pb and Cu appear to be supplied by quickflow processes and transported in close association with fine sediment, whereas Zn and Cd are delivered to the channel and lake by slower subsurface seepage in dissolved form. In the winter 2001 event, antecedent soil moisture and shallow groundwater levels were anomalously high and seepage sources of dissolved metals dominated. Downstream of the lake, Pb and Cu levels and suspended sediment were high in the summer storm, but low in the winter storm, suggesting retention with deposition of fine sediment in the lake during the latter. In the winter storm, Zn and Cd levels were higher downstream than upstream of the lake, perhaps because of additional seepage inputs from the surrounding slopes, which failed to have an impact during summer. An understanding of the complex interplay of antecedent soil moisture and the dynamics of subsurface seepage pathways in relation to the three‐dimensional distribution of sources is important in modelling heavy metal fluxes and levels in contaminated urban catchments. Copyright © 2003 John Wiley & Sons, Ltd.

Predicting floodplain boundary changes following the Cerro Grande wildfire

AbstractA combined ArcView GIS–HEC modelling application for floodplain analysis of pre‐ and post‐burned watersheds is described. The burned study area is located on Pajarito Plateau near Los Alamos National Laboratory (the Laboratory), where the Cerro Grande Wildfire burned 42 878 acres (17 352 ha) in May 2000. This area is dominated by rugged mountains that are dissected by numerous steep canyons having both ephemeral and perennial channel reaches. Vegetation consists of pinon–juniper woodlands located between 6000 and 7000 ft (1829–2134 m) above mean sea level (MSL), and Ponderosa pine stands between 7000 and 10000 ft MSL (2134–3048 m). Approximately 17% of the burned area is located within the Laboratory, and the remainder is located in upstream or adjacent watersheds. Pre‐burn floodplains were previously mapped in 1990–91 using early HEC models as part of the hazardous waste site permitting process. Precipitation and stream gauge data provide essential information characterizing rainfall–runoff relationships before and after the fire. They also provide a means of monitoring spatial and temporal changes as forest recovery progresses. The 2000 summer monsoon began in late June and provided several significant runoff events for model calibration. HEC–HMS modelled responses were sequentially refined so that observed and predicted hydrograph peaks were matched at numerous channel locations. The 100 year, 6 h design storm was eventually used to predict peak hydrographs at critical sites. These results were compared with pre‐fire simulations so that new flood‐prone areas could be systematically identified. Stream channel cross‐sectional geometries were extracted from a gridded 1 ft (0·3 m) digital elevation model (DEM) using ArcView GIS. Then floodpool topwidths, depths, and flow velocities were remapped using the HEC–RAS model. Finally, numerous surveyed channel sections were selectively made at crucial sites for DEM verification. These evaluations provided timely guidance that influenced the decision to construct several flood detention structures that were completed in September 2000. Published in 2001 John Wiley & Sons, Ltd.

On the Flood Control of Taihu Basin and Immediate Flood Control Standards

通过分析太湖流域自然、社会经济以及流域面临的防洪形势,认识流域防洪标准偏低、流域防洪体系建设不适应经济高速发展等问题.从现实和可能的角度分析论证流域防洪、区域防洪及城市防洪三个层次的标准,同时从统筹兼顾、蓄滞并重、完善提高、科学调度的原则出发提出了近期太湖流域防洪标准的设想.;Through analysis of the physical, social, economic situation of Taihu Basin, some problems of flood control of the whole basin are recognized, i.e.the flood control standard is lower, the construction of flood control system can not meet the rapid development of economics in the Basin, etc.In view of practicability and possibility, the future flood control standards should be re-examined in three levels city, regional and whole basin.The immediate flood control standard is put forward according to the rule of unified planning, couple flood detention with storage, improvement of Flood Regulation Scheme of Taihu Basin, and scientific regulation, etc.

Hydrodynamic Modeling of Wetlands for Flood Detention

The application of a link-node model in modeling hydrodynamics of wetland areas related to flood detention design is presented through the description of modeling and design efforts of an actual project, the first privately-owned wetland mitigation bank in Florida. The 142-ha project is located in the Chapel Trail Preserve of the City of Pembroke Pines, South Florida, where a degraded site is transformed into a healthy, self-sustaining wetland ecosystem. Creation of the wetlands, located adjacent to an existing development, required careful evaluation of drainage conditions. To properly design the wetland site, a hydrodynamic model was developed which allowed sizing of hydraulic structures and computation of maximum water surface elevations. The paper presents model description and calibration using field data, parameter sensitivity, general application in the project and use as a design tool. The model was found to be a valuable tool that can be applied in similar projects.

Reliability analysis of hydraulic structures considering unit hydrograph uncertainty

Unit hydrographs (UHs), along with design rainfalls, are frequently used to determine the discharge hydrograph for design and evaluation of hydraulic structures. Due to the presence of various uncertainties in its derivation, the resulting UH is inevitably subject to uncertainty. Consequently, the performance of hydraulic structures under the design storm condition is uncertain. This paper integrates the linearly constrained Monte-Carlo simulation with the UH theory and routing techniques to evaluate the reliability of hydraulic structures. The linear constraint is considered because the water volume of each generated design direct runoff hydrograph should be equal to that of the design effective rainfall hyetograph or the water volume of each generated UH must be equal to one inch (or cm) over the watershed. For illustration, the proposed methodology is applied to evaluate the overtopping risk of a hypothetical flood detention reservoir downstream of Tong-Tou watershed in Taiwan.

Field Experiment on Erosion-Resistance of Embankment of Ichinoseki Flood Detention Basin against Overflow.

Erosion resistance of a river bank slope with variety of plants was exeperimentally investigated. The experiment was carried out on a natural embankment of Ichinoseki Flood Detention Basin under rapid overflow condition. It is found that erosion resistance of embankment is governed by not only difference of distribution of plants but also mole holes in the bank.

Fenay Beck Flood-Alleviation Scheme

The paper describes flood detention and channel improvement schemes which have been designed to alleviate the flooding of domestic and industrial properties to a 50-year standard of protection. Landscape architects were incorporated into the design teams to cover environmental aspects

Phosphorus Dynamics in Agricultural Runoff and Reservoirs in Oklahoma

ABSTRACT Concentrations of soluble and total phosphorus in runoff from 16 grassed and cropped watersheds were measured over the past decade. Six watersheds drained into two flood detention reservoirs, where phosphorus concentrations were also measured at the inflow, within the lake, and at the outflow over a two-year period, to assess the effects of agricultural management practices on water quality. Soluble and total phosphorus concentrations in runoff from the native grass (133 and 343 mgP m−3, respectively) and cropped watersheds (215 and 2423 mgP m−3, respectively) were similar to phosphorus concentrations at the inflows to the reservoirs. Adsorption, biological uptake, and suspended sediment settling reduced soluble and total phosphorus levels 75 and 93 percent, respectively, in outflow from the reservoir with the grassed drainage basin and 72 and 96 percent, respectively, for the cropped drainage basin reservoir. Mean annual chlorophyll a and Secchi depths classified both reservoirs as eutrophic, even though only small amounts of fertilizer phosphorus were applied in their watersheds. Chlorophyll a and Secchi depths predicted from flushing-corrected inflow phosphorus concentrations were within the 95 percent confidence intervals of trophic response curves. Although flushing-corrected inflow phosphorus concentrations from native grass were appreciably lower than from cropped land, all management practices contributed runoff capable of accelerating eutrophication of the reservoirs.

Benthic Diatoms in Two Eutrophic Flood Detention Reservoirs in Oklahoma

ABSTRACT Benthic diatom colonization was observed for three years in two eutrophic flood detention reservoirs in Oklahoma. A total of 34 genera and 157 species were identified. Cocconeis placentula, Nitzschia amphibia and Achnanthes linearis were the dominant species. The average species diversity was lower and the population density was higher in the more eutrophic reservoir.

Value of On-Line Hydrologic Information for the Operation of a Multi-Purpose Reservoir

In this paper, a contribution is given to assess the benefits coming from on-line hydrologic information systems for the operation of multi-purpose reservoirs. Such systems are particularly useful for short-term analyses and hence the value of that information is estimated herein in terms of its use to study rapid hydrolonic events, namely high flows periods. Using data coming from a real system, developed in river Mondego (Portugal), this estimation is carried out for the operation of the reservoir during such periods as well as for the adaptive control of the flood detention storage, V, which implies the substitution of the well-known “upper guide curve” by an alternative concept of “upper guide function” which is proposed herin. For a given V, the annual flood risk, a, can be significantly decreased by elementary hydrolonic forecasts and for a given α a substantial reduction of expected V can be achieved by the adaptive control of V which is equivalent in this case to an average increase of the annual newer generation equal to 15 Cwh (about 780, 000 US dol. using 1931 prices).

Suspended Sediment‐Phosphorus Relationships for the Inflow and Outflow of a Flood Detention Reservoir

AbstractCallahan Reservoir, located in an agricultural area near Columbia, Missouri, was studied for 3 years to determine the inflow and outflow suspended sediment phosphorus (P) and the solution P relationships. During the study, the mean inflow solution ortho‐P concentration was 0.085 mg/liter as compared with 0.041 mg/liter for the outflow. Concentrations of ortho‐P were highest in both the inflow and outflow during the fall and winter. As yearly suspended sediment concentrations decreased in both the inflow and outflow, due to lower runoff and sediment yields, solution ortho‐P (mg/liter), as well as sediment total, inorganic, organic, and exchangeable P concentrations (µg/g), increased. Similarly, as a result of coarse sediment deposition within the reservoir during individual storm events, outflow sediments were enriched in clay and had higher concentrations (µg/g) of total, inorganic, organic, and exchangeable P than inflow sediments. However, because of sediment deposition within the reservoir, outflow volume concentrations (mg/liter) of sediment total P decreased fourfold as compared with inflow sediments.

Flood Management for Small Urban Streams

Experiences in Princeton, N.J. are drawn on to analyze flood problems of small urban streams, including building in flood plains, increased floods due to urbanization, and accentuated erosion tendencies. A detailed survey and flood analysis were very beneficial, followed by flood plain zoning, and a requirement for flood detention storage by developers. Culverts now too small to handle increased floods constitute a defense against erosion also caused by the floods. Reconsideration of criteria for culvert design in such situations would be valuable. Federal programs fall short of meeting the rather complex problems in small urbanizing watershed.

PRELIMINARY HYDROLOGIC DESIGN OF SMALL FLOOD DETENTION RESERVOIRS1

ABSTRACT. Flood detention reservoir design is a common problem encountered by engineers and others involved with water resources problems. This paper presents a method by which the volume of flood storage required for a single reservoir or a series of reservoirs may be estimated without using numeric flood‐routing techniques. The proposed procedure requires a minimum of computations and is most applicable to preliminary design situations where a high degree of accuracy is not required.

Highlights of Water Management in the Southwest Florida Water Management District

ABSTRACTThe District, comprising 15 counties and nearly 10,000 square miles in central western Florida centering on the Tampa‐St. Petersburg metropolitan area, is one of the nation's most rapidly growing areas. Water‐budget analyses compared with expected water demands for water by the burgeoning population indicate that by about 1985, if the present population growth rates and water‐use demands persist, we will be using as much water as nature supplies us with on the long‐term average annual basis, for once‐only uses. After that, to supply the water needed, we will either “mine” water on a District‐wide scale or bring about other remedies. Among these are, without attempting to list them in order of priorities: Reuse water again and again by cleaning it up and recharging the aquifers with both high‐grade sewage effluent either by land‐spreading or by injection through recharge wells into the aquifers. Engage in desalination of the almost limitless quantities of brackish ground water, especially in the coastal areas where salt‐water encroachment is occurring on a large scale. Induce aquifer recharge by creating storage space in the aquifers in areas that are currently full to overflowing. In such areas precipitation is now largely rejected as recharge and ground‐water seepage is lost to evapotranspiration. Effect economies of water use by both industry and agriculture—by far the largest users of water in our District—by regulation of amounts that may be used for irrigation and for various other industrial and agricultural processes. Divert flood waters from direct runoff to the oceans to temporary flood detention areas from which water can be drawn off to aquifer recharge facilities. By permit processes regulate the amounts of water that can be withdrawn for any purpose from either ground‐or surface‐water sources in the District thus preventing overdraft and resultant lowered water levels and, in some areas additional salt‐water encroachment. Eliminate waste of water, particularly the existing large losses from thousands of existing wild‐flowing artesian wells. Develop new, large well fields upgradient from the large coastal springs that now are discharging along our Gulf Coast, a total of about 900 mgd, none of which is now used for water supply. Space new well fields for regional water‐supply purposes widely over the District and arrange for organization of regional water‐distribution and use systems. As soon as feasible engage in rainmaking to augment nature's normal precipitation. Under nature's irrigation supply‐demand pattern and man's previously unmanaged and all‐too‐often wasteful usage growing beyond all previous expectations, the water supply and the flood‐and‐drought situation have become impossible to live with. But with proper management of our water and land resources the tide can be changed, and it will be possible to live comfortably within our available resources. It will cost us more but the increased cost is the price we must pay to live in an area where demands on the water resources are rapidly outgrowing nature's provisions.

Industrial Use of Reclaimed Sewage Water at Amarillo

THE prolonged drought in the Southwest has emphasized the importance of water to municipalities, agriculture, and industry. In many underground supplies, the rate of withdrawal is exceeding the rate of recharge. Small upstream flood detention reservoirs for the protection of creek valleys dissipate water in some degree. Moreover, the great population and industrial growth experienced by the area during the last decade has necessarily been accompanied by ever increasing demands for water.