Novel mass-aggregation-based calibration of an acoustic method of monitoring bedload flux by infrequent desert flash floods

The monitoring of bedload flux under flash flood conditions has been successfully achieved since 1992 using slot samplers in the semiarid Nahal Eshtemoa. In the present study, a surrogate bedload monitoring technique - the Japanese plate microphone - has been deployed and calibrated against data from the slot samplers. Since a slot sampler has a sensitivity threshold that becomes especially important when transport rates are low, different averaging periods should be considered for high and low fluxes. In order to overcome the deficiencies of time-based aggregation used hitherto, we have developed a new method involving mass aggregation and commensurably variable intervals, thereby enabling a more accurate analysis and optimizing the bedload sampler's capabilities. The data derived with this new method has then been utilized to calibrate the Japanese plate microphone. The Eshtemoa is an ephemeral gravel bed channel with a high proportion of fine gravel (< 0.02 m); for these conditions, acoustic sensors have not been calibrated as yet. Two multiple linear regression models incorporating the effect of median bedload grain size on pulse rate have been established to predict bedload flux and cumulative transported bedload mass. The coefficients in these models are statistically significant. Good predictions are obtained for bedload flux (adj. r² = 0.83) and for cumulative bedload mass (adj. r² = 0.98) during flood recession. Overall, the multiple linear regression models, used in conjunction with the mass aggregation method of estimating bedload flux, suggest that field calibration of acoustic devices is feasible under these conditions for ca. 90% of the duration of bedload transport. © 2020 John Wiley & Sons, Ltd.     

The benefits of a high-resolution analysis of transit accessibility

Accessibility is an important consideration in sustainable mobility policies, particularly for transit users. Measures suggested in the literature are based on coarse aggregate spatial resolution of traffic analysis zones that is sufficient for managing car travels only. To reflect a human door-to-door travel, transit accessibility demands an explicit view of the location of origin, transit stops and destination, as well as of the temporal fit between transit lines timetable and traveler’s needs. We thus estimate transit accessibility based on mode-specific travel times and corresponding paths, including walking and waiting, at the resolution of individual buildings and stops. Car accessibility is estimated at a high resolution too. A novel representation of transit network as a graph is proposed. This representation includes all modal components of a transit travel – walking, waiting at a stop, transit ride, transfers between lines, thus enabling unified view of a travel, regardless of mode. The use of modern high-performance graph database allows construction of high-resolution accessibility maps for an entire metropolitan area with its 100–200 K buildings. The application is tested and applied in a case study involving the evaluation of the 2011 bus line reform in the city of Tel Aviv. Specifically, we demonstrate that while the reform increased the average accessibility for the entire city the increase was not uniform with different areas of the city experiencing different absolute accessibility by transit and relative accessibility in comparison to car travel. The bus reform did in fact benefit travelers that experienced low relative accessibility, but the benefits are mainly accruing to longer trips. Our approach and computational methods can be employed for directly investigating the impacts of transportation infrastructure investments.     

The dynamics of Uranus' satellites

Current knowledge of the dynamics of Uranus' satellites is reviewed in support of preliminary planning for a mission to that planet. The determination of past and present orbital and rotational behavior is discussed. Improved understanding in this area is important not only for its own sake, but also for the implications with regard to the structure of the planet and to the general dynamical history of the solar system. A program of Earth-based observations over the next few years would permit most effective use of a Uranus probe.     

A numerical model investigation of tidal phenomena in the Bay of Fundy and Gulf of Maine

A numerical model is developed to examine tidal properties of the Bay of Fundy and Gulf of Maine. The model is run with a pure M₂ tidal input on the open boundary, and calibrated by adjusting the friction coefficient to achieve good agreement with inshore observations. An examination of aspects of the tidal regime is made, with particular attention paid to the upper reaches of the bay. Mean energy and work values are computed. The fundamental period of the system is estimated. The effects of tidal power plants on the tidal regime are examined.     

Planetary close encounters: geometry of approach and post-encounter orbital parameters

Öpik's assumptions on the geometry of particle trajectories leading to and through planetary close encounters are used to compute the distribution of changes in heliocentric orbital elements that result from such encounters for a range of initial heliocentric orbits. Behaviour at encounter is assumed to follow two-body (particle—planet) gravitational scattering, while before and after encounter particle motion is only governed by the force of the Sun. Derivation of these distributions allows precise analysis of the probability of various outcomes in terms of the physical characteristics of the bodies involved. For example, they allow an explanation and prediction of the asymmetry of the extreme energy perturbations for different initial orbits. The formulae derived here may be applied to problems including the original accumulation of planets and satellites, and the continuing evolution of populations of small bodies, such as asteroids and comets.     

Some spatial aspects of environmental impact statements in Israel

While many studies have analyzed EIS procedures, only a few have analyzed EISs as part of the development process. When viewed from this perspective, EISs are shown to have a skewing effect on territorial development; they address mainly infrastructure projects, and consequently delay them, but hardly touch any of the residential projects which the infrastructure is designed to serve. This discrepancy can have deleterious consequences due to residential encroachment on various infrastructure facilities, as well as due to the growing shortfall of transport and environmental infrastructure. When EISs are analyzed in terms of project area, areas where impacts and benefits are felt, and administrative control zones, it becomes apparent that the impacts and benefits analyzed may be affected by the spatial scope of administrative control and project areas. A case in point is the ‘Kalanit’ landfill in Israel. Here the benefit and impact areas analyzed in the EIS were affected by the jurisdiction of the committee that requested the EIS and to which it was submitted. This discrepancy between benefit, impact and administrative control areas is also at the source of the emerging interest in cross-boundary EIA.     

Erosional unloading,hillslope geometry,and the height of the Cascade Range,Washington State,USA

Peaks in the Cascade Range in northern Washington State are on average ～800 m higher than in southern Washington. The influences of differential valley excavation and variations in hillslope length and average slope on these altitudinal trends were tested using a 3‐dimensional model for isostatic rock uplift and calculations of hillslope length and slope respectively. The magnitude of isostatic peak uplift calculated by the model is highly dependent on the flexural rigidity (D) and the related effective elastic thickness (T_e) of the crust of this region. Crustal rigidity was constrained using published estimates and by estimating the depth of the seismogenic zone in the area (D > 1 × 10²³ Nm and T_e > 24 km). With these constraints, isostatic compensation due to differential erosion added < 700 m and 300 m, or < 25% overall, of height to peaks in the northern and southern Cascades, respectively. Deeper valley incision in the northern Cascades accounts for < 300 m of the 800 m difference in peak altitudes between north and south. Similarly, variation in valley spacing and slope account for < 350 m of the difference in mean altitude between northern and southern regions. Hence, at least several hundred m difference in altitude between the northern and southern regions of the Cascades in Washington must be due to tectonic, geologic, or geophysical factors rather than surficial and geomorphic effects like isostatic response to valley incision and hillslope geometry. Copyright © 2009 John Wiley & Sons, Ltd.     

Identifying synergies and trade-offs in the sustainability–security nexus: the case of the Israeli–Palestinian wastewater treatment regime

ABSTRACT

The literature on environmental security often stresses the complementarity between sustainability and broader security goals. Less emphasis has been placed on possible trade-offs between security objectives and aspects of sustainability. This study examines the conditions under which these synergies and trade-offs are likely to occur, and how the trade-offs can be reconciled, especially during times of peacebuilding. As a case study, we analyse the effect of Israeli security concerns on environmental infrastructure designed to treat wastewater in the West Bank. This study identifies several sustainability–security trade-offs: (1) economic—in which security concerns raise costs of wastewater infrastructure, thereby crowding-out other potentially productive investments; (2) equity—in which security concerns result in disproportionate exposure of populations to environmental hazards; and (3) environmental—in which security concerns increase ecological footprints. Yet, our case study also indicates that both sides used a variety of creative measures to reconcile these trade-offs.

EDITOR D. Koutsoyiannis GUEST EDITOR K. Aggestam     

A Melt-through Model for Chaos Formation on Europa

The character of chaotic terrain on Europa is consistent with its formation by the melting of a thin conducting ice shell from below. Tidal dissipation can provide adequate energy for such a process. For example, only a few percent of Europa's predicted tidal heat, spread over a region 200 km in diameter, can lead to large melt regions within a few tens of thousands of years. Stronger, more localized concentrations result in melt-through in significantly shorter times (i.e., a few hundred years). The time scale for melt-through is shorter than the time scale for the solid-state viscous inflow of ice by several orders of magnitude. In general, modest concentrations of tidal heat can melt ice away faster than viscous inflow, leading to melt-through. A mechanism to transmit these heat concentrations through the ocean is required for this model. Such heat transport could be the result of convective plumes in the ocean driven by seafloor volcanism or by the destabilization of a stratified ocean.