The triple-bottom-line: framing of trade-offs in sustainability planning practice

Sustainability principles are at the forefront of regional planning. In Hawaii, the movement toward “sustainability” gave way to revisiting the State Plan. This paper uses a case study of the Hawaii 2050 Sustainability Plan (Hawaii 2050) to illustrate how adopting popular notions of sustainability, without critical examination of how the respective policy frames diverge or interrelate, can lead to “tautological traps.” In the case of Hawaii 2050, the “triple-bottom-line” (embedded within sustainable development) became the dominant sustainability frame during the solicitation of public input and was thus used to guide the planning discourse. The application of triple-bottom-line concepts at the level of policy and planning led to a process that polarized economic and environmental interests. While the goals of sustainable development and the use of triple-bottom-line concepts are useful for planners, we argue that they should be applied within the parameters of ecological sustainability in a US regional context, lest resulting plans continue to allow the momentum of development to override ecological concerns.     

Development and Testing of a Physically Based Model of Streambank Erosion for Coupling with a Basin‐Scale Hydrologic Model SWAT

A comprehensive streambank erosion model based on excess shear stress has been developed and incorporated in the hydrological model Soil and Water Assessment Tool (SWAT). It takes into account processes such as weathering, vegetative cover, and channel meanders to adjust critical and effective stresses while estimating bank erosion. The streambank erosion model was tested for performance in the Cedar Creek watershed in north‐central Texas where streambank erosion rates are high. A Rapid Geomorphic field assessment (RAP‐M) of the Cedar Creek watershed was done adopting techniques developed by the Natural Resources Conservation Service (NRCS), and the stream segments were categorized into various severity classes. Based on the RAP‐M field assessment, erosion pin sites were established at seven locations within the severely eroding streambanks of the watershed. A Monte Carlo simulation was carried out to assess the sensitivity of different parameters that control streambank erosion such as critical shear stress, erodibility, weathering depth, and weathering duration. The sensitive parameters were adjusted and the model was calibrated based on the bank erosion severity category identified by the RAP‐M field assessment. The average observed erosion rates were in the range 25‐367 mm year^?1. The SWAT model was able to reasonably predict the bank erosion rates within the range of variability observed in the field (R² = 0.90; E = 0.78). Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.     

Modeling heterogeneous ClNO2 formation,chloride availability,and chlorine cycling in Southeast Texas

Nitryl Chloride (ClNO₂) mixing ratios above 1 ppbv have been measured off the coast of Southeast Texas. ClNO₂ formation, the result of heterogeneous N₂O₅ uptake on chloride-containing aerosols, has a significant impact on oxidant formation for the Houston area. This work reports on the modeling of ClNO₂ formation and describes the sensitivity of ClNO₂ formation to key parameters. Model sensitivity analyses found that: (1) Chloride availability limits the formation of nitryl chloride at ground level but not aloft; (2) When excess particulate chloride was assumed to be present at ground level through sea salt, ClNO₂ concentrations increased in some locations by a factor of 13, as compared to cases where sea salt chloride was assumed to be limited; (3) Inland formation of ClNO₂ seems feasible based on chloride availability and could have a large impact on total ClNO₂ formed in the region; and (4) ClNO₂ formation is quite sensitive to the assumed yield of ClNO₂ from N₂O₅ uptake. These results demonstrate that there is a need for further field studies to better understand the geographic extent of ClNO₂ formation and the atmospheric conditions which control partitioning of chloride into the particle phase. In addition, this work examined the role of ClNO₂ in the cycling of chlorine between chloride and reactive chlorine radicals. The modeling indicated that the majority of reactive chlorine in Texas along the Gulf coast is cycled through ClNO₂, demonstrating the importance of including ClNO₂ into photochemical models for this region.