REHABILITATION OF WATERSHEDS WITH INCISING CHANNELS1

ABSTRACT: Channel incision is a pervasive problem that threatens infrastructure, destroys arable land, and degrades environmental resources. A program initiated in 1983 is developing technology for rehabilitation of watersheds with erosion and sedimentation problems caused by incision. Demonstration projects are located in 15 watersheds in the hills of northwest Mississippi. Watershed sizes range from 0.89 to 1,590 km², and measured suspended sediment yields average about 1,100 t km^-2-yr^-1. Water quality is generally adequate to support aquatic organisms, but physical habitat conditions are poor. Rehabilitation measures, which are selected and laid out using a subjective integration of hydraulic and geotechnical stability analyses, include grade controls, bank protection, and small reservoirs. Aquatic habitat studies indicate that stone-protected stilling basins below grade-control weirs and habitats associated with drop pipes and stone spur dikes are assets to erosion-damaged streams. Additional recovery of habitat resources using modified stone stabilization designs, woody vegetation plantings, and reservoir outlets designed to provide non-zero minimum flows is under investigation.     

Designing Impact Assessments for Evaluating Ecological Effects of Agricultural Conservation Practices on Streams1

Abstract: Conservation practices are regularly implemented within agricultural watersheds throughout the United States without evaluating their ecological impacts. Impact assessments documenting how habitat and aquatic biota within streams respond to these practices are needed for evaluating the effects of conservation practices. Numerous sampling protocols have been developed for monitoring streams. However, protocols designed for monitoring studies are not appropriate for impact assessments. We developed guiding principles for designing impact assessments of ecological responses to conservation practices. The guiding principles are as follows: (1) develop the hypothesis first, (2) use replicated experimental designs having controls and treatments, (3) assess the habitat and biological characteristics with quantitative and repeatable sampling methods, (4) use multiple sampling techniques for collecting aquatic organisms, and (5) standardize sampling efforts for aquatic organisms. The guiding principles were applied in designing a study intended to evaluate the influence of herbaceous riparian buffers on channelized headwater streams in central Ohio. Our example highlights that the application of our recommendations will result in impact assessments that are hypothesis‐driven and incorporate quantitative methods for the measurement of abiotic and biotic attributes.     

Ability of Remnant Riparian Forests,With and Without Grass Filters,to Buffer Concentrated Surface Runoff1

Knight, Kris W., Richard C. Schultz, Cathy M. Mabry, and Thomas M. Isenhart, 2010. Ability of Remnant Riparian Forests, With and Without Grass Filters, to Buffer Concentrated Surface Runoff. Journal of the American Water Resources Association (JAWRA) 46(2):311-322. DOI: 10.1111/j.1752-1688.2010.00422.x Abstract: Riparian forest buffers established according to accepted conservation practice standards have been recommended as one of the most effective tools for mitigating nonpoint source pollution. The midwestern United States is characterized by many kilometers of narrow, naturally occurring forests along streams. However, little is known about the relative effectiveness of these remnant forests compared with these newly established buffers. This study compared the ability of naturally occurring remnant forests with and without adjacent planted grass filters to buffer concentrated flow paths (CFPs) originating in crop fields along first- and second-order streams in three northeast Missouri watersheds. Remnant forests breached by runoff through CFPs were narrower than those that dispersed 100% of the CFPs. Remnant forests with adjacent grass buffers were nearly twice the width as those without grass filters. We also found that CFPs, which developed within remnant forests and at the base of in-field grass waterways, were potential sources of sediments to streams. Methods to mitigate these CFPs warrant further investigation. Our study suggests that although these natural remnant forests provide substantial buffering capacity, both improved management and/or the addition of an adjacent grass filter would improve water quality by reducing sediment loss to streams. Inferences can be used to inform the design and management of similar conservation buffer systems within the region.     

Slip initiation in alternative and slip-resistant footwear

Slips occur as a result of failure of normal locomotion. The purpose of this study is to analyze the impact of alternative footwear (Crocs?, flip-flops) and an industry standard low-top slip-resistant shoe (SRS) under multiple gait trials (normal dry, unexpected slip, alert slip and expected slip) on lower extremity joint kinematics, kinetics and muscle activity. Eighteen healthy male participants (age: 22.28?±?2.2 years; height: 177.66?±?6.9?cm; mass: 79.27?±?7.6?kg) completed the study. Kinematic, kinetic and muscle activity variables were analyzed using a 3(footwear)?×?4(gait trials) repeated-measures analysis of variance at p?=?0.05. Greater plantar flexion angles, lower ground reaction forces and greater muscle activity were seen on slip trials with the alternative footwear. During slip events, SRS closely resembled normal dry biomechanics, suggesting it to be a safer footwear choice compared with alternative footwear.     

Sensitivity Analysis of Aggregated Indices for Integrated Assessment with a Case Study of the Mid-Atlantic Region

Environmental indicators are often aggregated into a single index for various purposes in environmental studies. Aggregated indices derived from the same data set can differ, usually because the aggregated indices' sensitivities are not thoroughly analyzed. Furthermore, if a sensitivity analysis is carried out, it is not presented in a transparent fashion to policy decision-makers. This paper presents a method of generating various aggregated environmental indices and analyzing their sensitivities via the use of the fuzzy set concept. Results show that several insights into the environmental conditions of the study area (e.g., the distribution of good or bad values of indicators at a watershed and or across the region) can be revealed in the sensitivity analysis of aggregated indices.     

Fates of cadmium introduced into channels microcosm

Five 10 μg Cd·l^?1 were continuously input to aquatic microcosm channels for one year. Cadmium accumulation in both biotic and abiotic components was determined. Cadmium inputs and outputs equilibrated within approximately 20 days of initial Cd inputs. Most community components accumulated Cd proportional to Cd water concentrations. Equilibrium Cd concentrations of sediments, aufwuchs, macrophytes, chironomids, and mosquito fish exposed to 10 μg Cd·l^?1 were 0.59, 55, 250, 40, and 40 μg Cd·g^?1, dry weight, respectively. Cadmium was rapidly eliminated from all biotic components when Cd inputs were terminated. Cadmium concentrations were similar to those in control channels within a few weeks in the aufwuchs community to a few months in macrophytes after Cd inputs were terminated. Cadmium uptake fluxes by the aufwuchs community and mosquito fish were first order, with respect to Cd concentration in the water. The rate constants for uptake and depuration for the aufwuchs community were 0.42 and 0.66 d^?1, respectively (concentration basis). The rate constants for uptake and depuration of Cd by mosquitofish were approximately 25 and 0.004 d^?1, respectively (concentration basis). Cadmium concentrations in organic headpool sediments had not significantly decreased six months after cessation of Cd inputs, which indicates that the abiotic half time for contaminated organic sediments is very long. Half times for elimination from channel sand sediments were 72 and 38 d for 5 and 10 μg·l^?1 exposure, respectively, after Cd inputs were terminated Cd concentrations in macroinvertebrates varied seasonally. The carrying capacity of the channels microcosm limited the number of samples of secondary and tertiary consumers which could be sampled. It was concluded that concluded that experimental channels of the size described here were not appropriate as screening tools for the fates of trace contaminants, but were effective for the study of trace contaminants, especially in conjunction with mathematical modeling efforts and less complex laboratory studies.     

Microbial influenced degradation of solidified waste binder

Ordinary cement pastes with water/cement (w/c) ratios of 0.2, 0.4 and 0.5 were used to examine the chemical and physical effects of microbial influenced degradation (MID). Samples were exposed to an active culture of Thiobacillus thiooxidans or to sterile media containing sulphuric acid using an intermittent immersion technique. Acid consumption and Ca, Al and Fe releases are presented for an exposure period of 90 days. Exposed samples were also sectioned and analysed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). All cement paste samples were subject to significant degradation in either sterile acid media or the T. thiooxidans lixiviant. Corrosion depths observed from SEM examination of exposed samples were affected by the w/c ratio of the cement. The extent and rate of degradation were not apparent from the calculated rate of hydrogen ion consumption, or the leaching rates of Ca, Al and Fe. It was not possible to distinguish differences in corrosion due to the chemical and microbial influenced degradation from the results obtained to date and further work is focusing on modified procedures to address this.