BEDLOAD TRANSPORT IN A POOL-RIFFLE SEQUENCE OF A COASTAL ALASKA STREAM1

ABSTRACT: A Helley-Smith pressure differential bedload sampler was used to measure bedload transport at consecutive riffle sections of a riffle-pool-riffle sequence on Bambi Creek, a small (154 ha), second-order stream on Chichagof Island, Alaska, during four storms over a 2-year period. Maximum bedload transport rate measured was 4920 kg/h at a streamflow of 2.35 m³/s corresponding to a storm having a 5-year return interval. Transport of larger sediment (> 8 mm) varied systematically with streamflow at the two sampling locations. At flows up to approximately bankfull, transport of large sediment was greatest at the upstream site; at flows above bankfull, transport of large sediment was greatest at the downstream site. The net import of large sediment to the pool during moderate stormflows and net export of large sediment from the pool during flows above bankfull may be related to a “convergence” or “reversal” of competence between the upstream riffle and subsequent pool at flows approximating bankfull stage. Cross-sections monitored within the study reach indicate that stormflows resulted in net filling of the riffle sections and net scour of the pool; periods of low streamflow resulted in net scour of the riffles and net filling of the pooL     

FRACTIONAL DIFFERENCING MODELING IN HYDROLOGY1

ABSTRACT: Fractional differencing is a tool for modeling time series which have long-term dependence; i.e., series in which the correlation between distant observations, though small, is not negligible. Fractionally differenced ARIMA models are formed by permitting the differencing parameter d in the familiar Box-Jenkins ARIMA(p, d, q) models to take nonintegral values; they permit the simultaneous modeling of the long-term and short-term behavior of an observed time series. This paper discusses the usefulness of fractional differencing to time-series modeling, with emphasis on hydrologic applications. A methodology for fitting fractionally differenced ARIMA models is described, and examples are presented.     

Impacts of hydroelectric development on riparian vegetation in the Sierra Nevada region,California, USA

Fourteen streams in the Sierra Nevada in the USA were sampled to determine whether diversions of streamflow for hydroelectric development had caused significant changes in riparian vegetation. Several streams showed significant differences in vegetation cover, community composition, or community structure between pairs of diverted and undiverted reaches. On some streams, environmental conditions rather than streamflow diversions may have been responsible for vegetation differences. Streams in the Sierra Nevada respond individualistically to diversions. Prediction of vegetation responses must take into consideration environmental characteristics of specific stream reaches.     

ALTERNATIVES TO THE USE OF AGRICULTURAL DRAINAGE WELLS1

ABSTRACT: A large number of agricultural drainage wells (ADWs) are located in north-central Iowa. These wells permit sediments, pesticides, nitrate, and bacteria in surface and subsurface drainage water to enter regional aquifers that are currently being used for drinking-water supplies, mostly by rural families and communities. This paper reports some possible alternatives to control the entry of surface and subsurface drainage waters into groundwater systems, and describes a methodology to make comprehensive economic feasibility studies of alternative drainage outlets. The estimated cost of providing main subsurface drains varied from $220 to $960 per hectare. If the use of ADWs was completely eliminated without providing alternative drainage, it is estimated that the average annual loss to the farmers of the area would be at least $270 per hectare in reduced crop yields. Of course, losses would be weather dependent and highly variable. Management practices to reduce the pollutant load in water draining to ADWs are also discussed.     

AN EVALUATION OF WEEKLY AND MONTHLY TIME SERIES FORECASTS OF MUNICIPAL WATER USE1

ABSTRACT: A cascade model for forecasting municipal water use one week or one month ahead, conditioned on rainfall estimates, is presented and evaluated. The model comprises four components: long term trend, seasonal cycle, autocorrelation and correlation with rainfall. The increased forecast accuracy obtained by the addition of each component is evaluated. The City of Deerfield Beach, Florida, is used as the application example with the calibration period from 1976–1980 and the forecast period the drought year of 1981. Forecast accuracy is measured by the average absolute relative error (AARE, the average absolute value of the difference between actual and forecasted use, divided by the actual use). A benchmark forecast is calculated by assuming that water use for a given week or month in 1981 is the same as the average for the corresponding period from 1976 to 1980. This method produces an AARE of 14.6 percent for one step ahead forecasts of monthly data and 15.8 percent for weekly data. A cascade model using trend, seasonality and autocorrelation produces forecasts with AARE of about 12 percent for both monthly and weekly data while adding a linear relationship of water use and rainfall reduces the AARE to 8 percent in both cases if it is assumed that rainfall is known during the forecast period. Simple rainfall predictions do not increase the forecast accuracy for water use so the major utility of relating water use and rainfall lies in forecasting various possible water use sequences conditioned on sequences of historical rainfall data.     

Impact of power utility rights-of-way on wooded wetland

This study documents the effects of power utility right-of-way construction and maintenance on the vegetation of a wooded wetland in North Reading, Massachusetts, USA. Neither activity had a substantial, long-term negative impact. Except for differences in size and maturity, the vegetation recovered in two years from nearly total destruction caused by construction. Maintenance that included the periodic removal of high-growing species led to the formation of a plant association different from the one occurring naturally, but as diverse and species rich.     

Behavioral risk and education: A united states case study

Summary Does educational achievement affect people's health-related behaviors? Differences in behavioral risk were found among 9,000 18 to 34 year old Americans surveyed for smoking, alcohol abuse, seat-belt-use, obesity, high blood pressure and physical activity. After controlling for sex, race/ethnicity and age, educational achievement was strongly associated with smoking and seat-belt use, and also with hypertension and obesity. New environmental health education programs in the USA are expected to reach the more educated, leading to enhanced health for most Americans, but not the less educated, resulting in a widening gap in American society.Dr Michael R. Greenberg is an Advisory Board member ofThe Environmentalist, he is Co-director of the Graduate Program in Public Health at Rutgers University and the University of Medicine and Dentistry of New Jersey - Robert Wood Johnson Medical School.     

Woody plant roots fail to penetrate a clay-lined landfill: Managment implications

In many locations, regulatory agencies do not permit tree planting above landfills that are sealed with a capping clay, because roots might penetrate the clay barrier and expose landfill contents to leaching. We find, however, no empirical or theoretical basis for this restriction, and instead hypothesize that plant roots of any kind are incapable of penetrating the dense clays used to seal landfills. As a test, we excavated 30 trees and shrubs, of 12 species, growing over a clay-lined municipal sanitary landfill on Staten Island, New York. The landfill had been closed for seven years, and featured a very shallow (10 to 30-cm) soil layer over a 45-cm layer of compacted grey marl (Woodbury series) clay. The test plants had invaded naturally from nearby forests. All plants examined—including trees as tall as 6 m—had extremely shallow root plates, with deformed tap roots that grew entirely above and parallel to the clay layer. Only occasional stubby feeder roots were found in the top 1 cm of clay, and in clay cracks at depths to 6 cm, indicating that the primary impediment to root growth was physical, although both clay and the overlying soil were highly acidic. These results, if confirmed by experimental research should lead to increased options for the end use of many closed sanitary landfills.     

Riparian buffers and potentially unstable ground

The spatial coincidence between riparian buffers of various widths and extents and potentially unstable ground was quantified using a physically based model for shallow landslide initiation and GIS for two watersheds on the Olympic Peninsula, Washington, USA. The proportion of the potentially unstable ground in each watershed within riparian buffers is a function of both buffer width and the extent of the stream channel network being buffered. While current buffers required by Washington State cover less than 5% of the potentially unstable ground, buffering all stream channels in these watersheds with 100-m buffers covered 75%–90% of the potentially unstable areas. Our analyses further show that: (1) riparian buffers are not efficient mechanisms for protecting potentially unstable ground, and (2) identifying potentially unstable ground using a physically based model should prove more effective for designing methods to reduce shallow landsliding hazards than relying on extensive buffer zones along stream channels.     

Design for environment: A new framework for strategic decisions

For most of its history of environmental protection, U.S. policy has concentrated on a pollution control strategy based on single medium emissions: air, water, or land. Efforts to mitigate environmental impacts to one medium often resulted in greater impacts to others. While much environmental improvement has occurred via this system over the last quarter-century, it is generally recognized that alternative strategies which address environmental impacts across all media in an integrated manner will be necessary for continued improvement. Increasingly, regulatory strategies that result in only passive compliance will be insufficient to meet these demands. This article demonstrates why new strategies which encourage proactive behavior are necessary. A new framework for making strategic decisions—design for environment—concerning the relation between our actions and environment is necessary to ensure a sustainable future.