EMERGING STATE ROLES IN URBAN STORMWATER MANAGEMENT1

ABSTRACT: The technology of urban stormwater management has far outpaced its actual application in new urban development. This article documents that implementation gap, but shows that state and local governmental measures, particularly storm drainage regulations, can lead to improved performance in the private sector. Although state stormwater management programs are in their infancy, they are already having a measurable effect in stimulating the adoption of local governmental programs to manage urban storm water. Pioneering state programs in Maryland, New Jersey, and Pennsylvania, described in this article, provide models for states contemplating the formulation of stormwater management programs.     

STATE-OF-THE-ART OF ESTIMATING FLOOD DAMAGE IN URBAN AREAS1

ABSTRACT: With implementation of the Flood Insurance Act of 1968 many additional local flood protection projects are being considered. Consulting engineers and local agencies need consistent methods to estimate flood damage in order to perform feasibility studies. Federal agencies have a great deal of data and long experience in making damage estimates but no comprehensive guides are available at the local level. Curves of flood damages to different residential structure types are presented. The relationships in use by the U. S. Federal Insurance Administration are shown to be reasonable and are recommended for use as approximate guides. Additional research is recommended and discussion of the paper is invited in order to make additional data available in the literature.     

A COMPARISON OF MODELS PREDICTING GROUND WATER LEVELS ON HILLSIDE SLOPES1

ABSTRACT: A comparative study of ground water level predictions on hillside slopes using two models is presented. The models are a simplified mass balance model that has components for evapotran-spiration, recharge, and drainage; and a two-dimensional finite difference model that employs kriging to estimate soil parameters and accounts for non-uniform thickness of the soil layer. These models are representative of a wide range of modeling capabilities and are used to illustrate the sensitivity of ground water level predictions to the sophistication of the modeling techniques. The drainage and recharge components of the two models are evaluated and the importance of unsaturated flow in recharge computations is underscored. Piezometric observations in a small drainage depression on the slope of Kennel Creek Valley in Tongass National Forest, Alaska, were used to evaluate the two models. The results show that, although the predictions differ from the field observations, the simple physically-based mass balance model predicts the ground water levels as well as the two-dimensional model. It is suggested that caution should be exercised in using complex models to validate simpler models.     

Minimizing contamination hazards to waterbirds using agricultural drainage evaporation ponds

In much of the San Joaquin Valley, California, USA, inadequate drainage of applied irrigation water and accumulating salts in the soil have necessitated the installation of subsurface tile drainage systems to preserve crop productivity. At present, these subsurface drainage waters are disposed of by means of evaporation ponds or discharges into the San Joaquin River. Unfortunately, most of these agricultural drainage waters contain high concentrations of salts and naturally occurring trace elements, such as selenium, and recent evidence indicates that substantial numbers of waterbirds are exposed to contamination by selenium in the evaporation ponds. In order to avoid, minimize, or mitigate the adverse impacts on wildlife using the ponds, alternative pond management methods must be identified and evaluated for implementation. A number of methods have the potential to be cost-effective in significantly reducing the contamination hazard to birds using agricultural evaporation ponds. Twenty general methods were evaluated in this study, and four methods are recommended for implementation: remove levee vegetation, remove windbreaks, deepen the ponds, and haze birds. A number of other methods are recommended for further consideration because they appear to have good prospects for reducing the contamination hazard: steepen interior levee slopes, apply herbicides and insecticides, place netting on pond shorelines, and provide freshwater habitat adjacent to evaporation ponds. It may be necessary to use a combination of methods to effectively control selenium contamination of aquatic birds because it is unlikely that a single affordable pond management method will be able to entirely eliminate the contamination hazard.     

DEVELOPMENT AND VERIFICATION OF A WATER BALANCE MODEL FOR SUBSURFACE DRAINAGE DESIGN1

ABSTRACT: A water balance model was developed to predict daily water table depths in some corn fields with or without subsurface drainage systems, using pertinent soil and water properties and weather data. The model outputs were compared with the recorded data of observed water table depths. Some statistical parameters such as the mean, standard deviation, the coefficient of correlation, the sum of the squares of deviations, and a nonparametric statistical test were used to study the extent of agreement between the observed and the predicted water table depths. No significant difference was found between the distributions of the observed and the predicted water table depths at the 99% confidence level. The study was conducted on some sand and clay soils of the Ottawa-St. Lawrence Lowlands region in Canada where there is a cool, moist climate and poor natural drainage.     

PETROLEUM HYDROCARBONS IN URBAN RUNOFF1

ABSTRACT: Estimates were made of petroleum hydrocarbon pollution loadings reaching the Delaware Estuary by determining storm event loadings of hydrocarbons from four storm sewers, draining areas of different land uses. Although refinery effluents constituted the largest source of petroleum pollution in 1975, it appears that after completion of currently required treatment processes urban runoff will be the largest remaining source of petroleum pollution. The petroleum in urban runoff resembles used crankcase oil in composition and contains toxic chemicals such as polynuclear hydrocarbons. Further research is clearly desirable. Remedial programs to control such pollution may be warranted on the basis of information now available.     

ACID MINE DRAINAGE (AMD) AND ITS IMPACT ON A SMALL VIRGINIA STREAM1

ABSTRACT: A study was conducted to 1) chemically characterize three AMD streams entering Chestnut Creek in southwestern Virginia below the town of Galax, Virginia, and 2) to assess the biological and chemical alterations in the creek. Over a six mile reach, the benthic macroinvertebrate population was reduced to zero, the naturally low alkalinity (～25mg/1) of the stream was reduced to less than 5 mg/1, and the pH was reduced from 7.2 to 6.3. Increased concentration of iron from less than 0.01 mg/I to more than 4.0 mg/1 were accompanied by the deposition of a coating of iron hydroxide up to 0.25 in. thick in the stream bed, a phenomenon most likely responsible for the absence of benethic macroinvertebrates. In situ bioassays with bluegill sunfish and one snail species showed that the creek water, after confluence with all the AMD streams, was not toxic in 192 hours to fish, and snails survived 96 hours before they began to die. The undiluted AMD itself was highly toxic.     

RUNOFF POLLUTION FROM MULTIPLE FAMILY HOUSING1

ABSTRACT: Increasingly, residential development in urbanizing areas is accomplished by large housing projects, composed of clusters of townhouses or garden partments. It is hypothesized that the runoff from such developments should carry more pollution than that from the same number of housing units on separate plots, because the runoff is conveyed directly to drainage channels rather than being drained across lawns and gardens, which may absorb part of the pollutants. In order to evaluate this effect, storm event data were obtained from a planned unit development near Hightstown, N. J., using samples taken every 10 minutes throughout the storm at two different storm sewers. Results show heavy metals pollution about what had been anticipated, in accordance with the hypothesis given above, and BOD ammonia and phosphates higher than predicted. The results are significant for areawide water quality planning in metropolitan areas, where projections of future pollution loadings depends upon the land use.     

SURFACE WATER RESOURCES OF NORTHWEST FLORIDA1

ABSTRACT: Of the 1,700 streams located in the state of Florida, the northwest area contains approximately 1,000 streams and three of the five largest rivers, namely the Apalachicola, the Choctawhatchee, and the Escambia. This 11,200 square-mile area contains 11 drainage basins and receives an average annual rainfall which ranges from 53 inches in the east to 67 inches in the west. Basin water yields range from a high of 3,376 cfs (2,180 mgd) to a low of 672 cfs (434 mgd). Individual basin outflows range from a high of 25,743 cfs (16,630 mgd) to a low of 844 cfs (545 mgd). Approximately 67 percent of the total northwest Florida basin outflows to the Gulf of Mexico, or 36,805 cfs (23,766 mgd), are received in the form of surface water inflows from Alabama and Georgia. In the absence of any interstate mechanism for water management between Alabama, Florida, and Georgia, the basin outflow estimates presented in this paper depend greatly on the upstream usage in the neighboring states. The establishment of a tri-state water management program could eliminate the uncertainty involved in predicting water availability in northwest Florida and ensure sufficient quantities of flows in the streams.