Stability analysis of the 2007 Chehalis lake landslide based on long-range terrestrial photogrammetry and airborne LiDAR data

On December 4th 2007, a 3-Mm³ landslide occurred along the northwestern shore of Chehalis Lake. The initiation zone is located at the intersection of the main valley slope and the northern sidewall of a prominent gully. The slope failure caused a displacement wave that ran up to 38 m on the opposite shore of the lake. The landslide is temporally associated with a rain-on-snow meteorological event which is thought to have triggered it. This paper describes the Chehalis Lake landslide and presents a comparison of discontinuity orientation datasets obtained using three techniques: field measurements, terrestrial photogrammetric 3D models and an airborne LiDAR digital elevation model to describe the orientation and characteristics of the five discontinuity sets present. The discontinuity orientation data are used to perform kinematic, surface wedge limit equilibrium and three-dimensional distinct element analyses. The kinematic and surface wedge analyses suggest that the location of the slope failure (intersection of the valley slope and a gully wall) has facilitated the development of the unstable rock mass which initiated as a planar sliding failure. Results from the three-dimensional distinct element analyses suggest that the presence, orientation and high persistence of a discontinuity set dipping obliquely to the slope were critical to the development of the landslide and led to a failure mechanism dominated by planar sliding. The three-dimensional distinct element modelling also suggests that the presence of a steeply dipping discontinuity set striking perpendicular to the slope and associated with a fault exerted a significant control on the volume and extent of the failed rock mass but not on the overall stability of the slope.     

How to assess hydromorphology? A comparison of Ukrainian and German approaches

Recently, the Ukrainian Western Bug water authorities developed a national field survey to assess the quality of river habitats. The Ukrainian government already cooperates with EU member states along transboundary rivers and also orientates itself towards the European Water Framework Directive (WFD). As a future application for EU membership is feasible, the water authorities started to implement WFD criteria into their national survey schemes including the assessment of rivers’ hydromorphology. This article compares two different hydromorphological survey methods to identify similarities and differences of the classification approaches with regard to the conformity of obtained outputs with the WFD demands. The field surveys, the Ukrainian (UA-FS) and the German (LAWA-FS), were applied in parallel on 14 river sections along the Western Bug River and parts of its tributaries. Results show a wide range of conformity, but also several differences between and gaps within all methods. The UA-FS generally lacks the idea of reference condition in rivers’ hydromorphology and the definition of different stream types or near-natural land uses. The UA-FS and the LAWA-FS approaches are similar with respect to their incorporated compartments and most main parameters, but differ in definition and interpretation of specific functional units and single parameters. Greatest similarities down to single parameters exist in aspects of land use, bank vegetation, currents diversity, and within-stream variation of water depths. Differences include the assessment and interpretation of lateral erosion, sinuosity, type and depth of profile, substrate diversity, as well as special structures of bank and riverbed. Overall, the LAWA-FS is more conservative in its rating than the UA-FS. Still, UA-FS can be regarded as an important improvement for a systematic and reliable monitoring of river hydromorphology in the Ukraine that will help to successfully engage with both the integrated water resources management and the WFD harmonisation process in the future.     

Morphological similarities between DBM and a microeconomic model of sprawl

We present a model that simulates the growth of a metropolitan area on a 2D lattice. The model is dynamic and based on microeconomics. Households show preferences for nearby open spaces and neighbourhood density. They compete on the land market. They travel along a road network to access the CBD. A planner ensures the connectedness and maintenance of the road network. The spatial pattern of houses, green spaces and road network self-organises, emerging from agents individualistic decisions. We perform several simulations and vary residential preferences. Our results show morphologies and transition phases that are similar to Dieletric Breakdown Models (DBM). Such similarities were observed earlier by other authors, but we show here that it can be deducted from the functioning of the land market and thus explicitly connected to urban economic theory.     

Dispersion of a Point-Source Release of a Passive Scalar Through an Urban-Like Array for Different Wind Directions

The dispersion of a point-source release of a passive scalar in a regular array of cubical, urban-like, obstacles is investigated by means of direct numerical simulations. The simulations are conducted under conditions of neutral stability and fully rough turbulent flow, at a roughness Reynolds number of Re _τ  = 500. The Navier–Stokes and scalar equations are integrated assuming a constant rate release from a point source close to the ground within the array. We focus on short-range dispersion, when most of the material is still within the building canopy. Mean and fluctuating concentrations are computed for three different pressure gradient directions (0°, 30°, 45°). The results agree well with available experimental data measured in a water channel for a flow angle of 0°. Profiles of mean concentration and the three-dimensional structure of the dispersion pattern are compared for the different forcing angles. A number of processes affecting the plume structure are identified and discussed, including: (i) advection or channelling of scalar down ‘streets’, (ii) lateral dispersion by turbulent fluctuations and topological dispersion induced by dividing streamlines around buildings, (iii) skewing of the plume due to flow turning with height, (iv) detrainment by turbulent dispersion or mean recirculation, (v) entrainment and release of scalar in building wakes, giving rise to ‘secondary sources’, (vi) plume meandering due to unsteady turbulent fluctuations. Finally, results on relative concentration fluctuations are presented and compared with the literature for point source dispersion over flat terrain and urban arrays.     

Hurricane effects on subtropical pine rocklands of the Florida Keys

We investigate the effects of Hurricane Wilma??s storm surge (23?C24 October 2005) on the dominant tree Pinus elliottii var densa (South Florida slash pine) and rare plant species in subtropical pine rocklands of the Lower Florida Keys. We examine the role of elevation on species abundance in 1995 (Hurricane Betsy in 1965), 2005 (Hurricane Georges in 1998), and 2008 (Hurricane Wilma in 2005) to investigate if hurricanes influence abundance by eliminating plants at lower elevation on Big Pine Key, the largest island in the Lower Florida Keys. We compare densities before and after Hurricane Wilma over the 2005?C2008 sampling period and examine the role of elevation on changes in pine and rare species densities three years after Hurricane Wilma. We use elevation to assess the impact of hurricanes because elevation determined whether a location was influenced by storm surge (maximum surge of 2 m) in the Lower Florida Keys, where pine rocklands occur at a maximum elevation of 3 m. In 1995 (30 years after a major storm), elevation did not explain the abundance of South Florida slash pine or Chamaecrista lineata, but explained significant variation in abundance of Chamaesyce deltoidea. The latter two species are rare herbaceous plants restricted to pine rocklands. In 2008, 3 years after Hurricane Wilma, the positive relationship between elevation and abundance was strongest for South Florida slash pine, C. deltoidea, and C. lineata. Effects of Hurricane Wilma were not significant for rare species with wider distribution, occurring in plant communities adjacent to pine rocklands and in disturbed rocklands. Our results suggest that hurricanes drive population dynamics of South Florida slash pine and rare species that occur exclusively in pine rocklands at higher elevations. Rare species restricted to pine rocklands showed dramatic declines after Hurricane Wilma and were eliminated at elevations <0.5 m. Widely distributed rare species did not show significant changes in density after Hurricane Wilma. Abundance increased with elevation for South Florida slash pine and C. lineata after the hurricane. In an environment influenced by sea level rise, concrete plans to conserve pine ecosystems are warranted. Results from this study will help define conservation strategies by strengthening predictive understanding of plant responses to disturbance in the backdrop of sea level rise.     

Response of hydrological cycle to recent climate changes in the Tibetan Plateau

The Tibetan Plateau (TP) surfaces have been experiencing an overall rapid warming and wetting while wind speed and solar radiation have been declining in the last three decades. This study investigated how climate changes influenced the hydrological cycle on the TP during 1984??2006. To facilitate the analysis, a land surface model was used to simulate surface water budget at all CMA (China Meteorological Administration) stations on the TP. The simulated results were first validated against observed ground temperature and observation-derived heat flux on the western TP and observed discharge trends on the eastern TP. The response of evaporation and runoff to the climate changes was then analyzed. Major finding are as follows. (1) Surface water balance has been changed in recent decades. Observed precipitation shows insignificant increasing trends in central TP and decreasing trends along the TP periphery while evaporation shows overall increasing trends, leading to decreased discharge at major TP water resource areas (semi-humid and humid zones in the eastern and southern TP). (2) At the annual scale, evaporation is water-limited in dry areas and energy-limited (radiation and air temperature) in wet areas; these constraints can be interpreted by the Budyko-curve. Evaporation in autumns and winters was strongly controlled by soil water storage in summers, weakening the dependence of evaporation on precipitation at seasonal scales. (3) There is a complementary effect between the simulated actual evaporation and potential evaporation, but this complementary relationship may deviate from Bouchet??s hypothesis when vapor pressure deficit (or air temperature) is too low, which suppresses the power of vapor transfer.     

Coherent structures and flux contribution over an inhomogeneously irrigated cotton field

The turbulence data measured at two levels (i.e., 8.7 and 2.7?m) in the Energy Balance Experiment (EBEX), which was conducted in San Joaquin Valley in California during the period from July 20 to August 24, 2000, are used to study the characteristics of coherent structures over an irrigated cotton field. Patch-to-patch irrigation in the field generated the dry-to-wet horizontal advection and the oasis effects, leading to the development of a stably internal boundary layer (SIBL) in the late mornings or the early afternoons. The SIBL persisted in the rest of the afternoons. Under this circumstance, a near-neutral atmospheric surface layer (ASL) developed during the period with a stratification transition from the unstable to stable conditions during the daytime. Therefore, EBEX provides us with unique datasets to investigate the features of coherent structures that were generated over the patches upstream and passed by our site in the unstable ASL, the near-neutral ASL, and the SIBL. We use an objective detection technique and the conditional average method that is developed based on the wavelet analysis. Our data reveal some consistencies and inconsistencies in the characteristics of coherent structures as compared with previous studies. Ramp-like structures and sweep?Cejection cycles under the daytime SIBL have similar patterns to those under the nocturnal stable ASL. However, some features (i.e., intermittence) are different from those under the nocturnal stable ASL. Under the three stratifications, thermal and mechanical factors in the ASL perform differently in affecting the ramp intensity for different quantities (i.e., velocity components, temperature, and specific humidity), leading to coherent structures that modulate turbulence flow and alter turbulent transfer differently. It is also found that coherent structures contribute about 10?C20% to the total fluxes in our case with different flux contributions under three stratifications and with higher transporting efficiency in sensible heat flux than latent heat and momentum fluxes.     

Defense community perspectives on uncertainty and confidence judgments

In 2007, the CNA Military Advisory Board (MAB), an expert panel composed of 11 retired admirals and generals from the United States, identified climate change as a “threat multiplier” for instability in some of the most volatile regions of the world. (CNA MAB National security and the threat of climate change 2007)The Department of Defense reached a similar conclusion in last year’s Quadrennial Defense Review–a legislatively mandated analysis of the Defense Department’s strategy and priorities. This document frames the long-term course for policy decision-making at the highest levels. The reports demonstrate that climate change and energy are now mainstream elements of national security planning, and can be assessed within the frameworks used to evaluate other threats, risks, and responses. However, the exact magnitude of the threat posed by climate change is difficult to calibrate in part because the language used by scientists to predict uncertainty and the confidence levels of judgments is not sufficiently clear. The defense community has a vast amount of experience exploring and dealing with uncertainty. Scientists trying to better describe the effects of climate change may be able to draw lessons from the defense community’s approach to uncertainty including how to better communicate findings to wide audiences including policy-makers.     

The Stanford Climate Change Behavior Survey (SCCBS): assessing greenhouse gas emissions-related behaviors in individuals and populations

Many individual-level behaviors are associated with greenhouse gas (GHG) emissions. Reliable and valid assessment instruments are needed to (1) identify behaviors and populations to target with emissions-reduction programs and policies, (2) evaluate the effectiveness of such programs, (3) link self-reported and objective measures of GHG emissions to establish the impact of specific behaviors, and (4) estimate frequencies of behaviors and their changes over time to aid policy makers in understanding energy consumption trends. The self-administered Stanford Climate Change Behavior Survey (SCCBS) is shown to be a reliable and valid instrument that can be used for these purposes in college students, and we anticipate that it will also be useful for assessing these behaviors in other adolescent or adult populations in developed countries. Questions included behaviors likely to be within the control of most individuals and did not include behaviors specific to home owners (e.g. appliance purchases). Ten indices were identified: Energy Use, No-, Low-, and High-GHG Transportation, Waste, Food Packaging, High- and Low-GHG Food, Food Purchasing, and GHG Credits use. A Total GHG Behavior score was calculated. Test–retest reliabilities of individual items ranged from .64 to .91. Internal consistency reliabilities for each of the indices ranged from .51 to .89. Most indices were statistically significantly correlated with one another. Correlational validity of the SCCBS was demonstrated with statistically significant associations between behavior scores and perceived importance of environmental sustainability and membership in an environmental organization. The use of the SCCBS to identify potential target sub-populations and behaviors was demonstrated.