GIS Methodology for Characterizing Historical Conditions of the Willamette River Flood Plain, Oregon

Recent environmental developments have stimulated an interest in conservation and restoration of the historical Willamette River flood plain, both to protect against flooding and to provide wildlife habitat. In order to best utilize scarce resources, we characterized historical and modern river channel and flood‐plain conditions to evaluate changes and help prioritize restoration sites. Using cartographic and photographic data sources, we developed a Geographic Information System (GIS) to map active channels, side channels, islands and tributaries for four separate dates, as well as riparian and flood‐plain vegetation characteristics for pre‐European settlement and modern time periods. Coverages based on flood records and other boundaries were used to partition the flood plain into spatial subsets for analysis. The GIS allowed comparisons between historical and present conditions for a variety of environmental factors. Much of the pre‐settlement channel complexity has been removed. Total channel length in 1995 was 26% less than in 1850, with almost 58% of the river's side channels disconnected from the system. In addition, we found a 72% loss of flood‐plain forest from 1850 to 1995, since it was converted to agricultural and urban land uses. Selected river and flood‐plain variables were made available for a spatial model to prioritize potential locations for flood‐plain restoration.     

The Science and Policy of the Verified Carbon Standard Methodology for Tidal Wetland and Seagrass Restoration

The restoration of tidal wetland and seagrass systems has the potential for significant greenhouse gas benefits, but project-level accounting procedures have not been available at an international scale. In this paper, we describe the Verified Carbon Standard Methodology for Tidal Wetland and Seagrass Restoration, which provides greenhouse gas accounting procedures for marsh, mangrove, tidal forested wetland, and seagrasses systems across a diversity of geomorphic conditions and restoration techniques. We discuss and critique the essential science and policy elements of the methodology and underlying knowledge gaps. We developed a method for estimating mineral-protected (recalcitrant) allochthonous carbon in tidal wetland systems using field-collected soils data and literature-derived default values of the recalcitrant carbon that accompanies mineral deposition. We provided default values for methane emissions from polyhaline soils but did not provide default values for freshwater, oligohaline, and mesohaline soils due to high variability of emissions in these systems. Additional topics covered are soil carbon sequestration default values, soil carbon fate following erosion, avoided losses in organic and mineral soils, nitrous oxide emissions, soil profile sampling methods, sample size, prescribed fire, additionality, and leakage. Knowledge gaps that limit the application of the methodology include the estimation of CH₄ emissions from fresh and brackish tidal wetlands, lack of validation of our approach for the estimation of recalcitrant allochthonous carbon, understanding of carbon oxidation rates following drainage of mineral tidal wetland soils, estimation of the effects of prescribed fire on soil carbon stocks, and the analysis of additionality for projects outside of the USA.     

Improvements in the integration of remote sensing and rock slope modelling

Natural Hazards - Forests are always dangerous to fire in China’s forested regions, and forest fire hazard has long been a serious issue in China. Zhejiang province is one of the key forest...     

Observing Global Surface Water Flood Dynamics

Flood waves moving along river systems are both a key determinant of globally important biogeochemical and ecological processes and, at particular times and particular places, a major environmental hazard. In developed countries, sophisticated observing networks and ancillary data, such as channel bathymetry and floodplain terrain, exist with which to understand and model floods. However, at global scales, satellite data currently provide the only means of undertaking such studies. At present, there is no satellite mission dedicated to observing surface water dynamics and, therefore, surface water scientists make use of a range of sensors developed for other purposes that are distinctly sub-optimal for the task in hand. Nevertheless, by careful combination of the data available from topographic mapping, oceanographic, cryospheric and geodetic satellites, progress in understanding some of the world’s major river, floodplain and wetland systems can be made. This paper reviews the surface water data sets available to hydrologists on a global scale and the recent progress made in the field. Further, the paper looks forward to the proposed NASA/CNES Surface Water Ocean Topography satellite mission that may for the first time provide an instrument that meets the needs of the hydrology community.     

Geomechanical property estimation of unconventional reservoirs using seismic data and rock physics

An extension of a previously developed rock physics model is made that quantifies the relationship between the ductile fraction of a brittle/ductile binary mixture and the isotropic seismic reflection response. By making a weak scattering (Born) approximation and plane wave (eikonal) approximation, with a subsequent ordering according to the angles of incidence, singular value decomposition analyses are performed to understand the stack weightings, number of stacks, and the type of stacks that will optimally estimate two fundamental rock physics parameters – the ductile fraction and the compaction and/or diagenesis. It is concluded that the full PP stack, i.e., sum of all PP offset traces, and the “full” PS stack, i.e., linear weighted sum of PS offset traces, are the two optimal stacks needed to estimate the two rock physics parameters. They dominate over both the second‐order amplitude variation offset “gradient” stack, which is a quadratically weighted sum of PP offset traces that is effectively the far offset traces minus the near offset traces, and the higher order fourth order PP stack (even at large angles of incidence). Using this result and model‐based Bayesian inversion, the seismic detectability of the ductile fraction (shown by others to be the important rock property for the geomechanical response of unconventional reservoir fracking) is demonstrated on a model characteristic of the Marcellus shale play.     

Carbon Stores,Sinks, and Sources in Forests of Northwestern Russia: Can We Reconcile Forest Inventories with Remote Sensing Results?

Forest inventories and remote sensing are the two principal data sources used to estimate carbon (C) stocks and fluxes for large forest regions. National governments have historically relied on forest inventories for assessments but developments in remote sensing technology provide additional opportunities for operational C monitoring. The estimate of total C stock in live forest biomass modeled from Landsat imagery for the St. Petersburg region was consistent with estimates derived from forest inventory data for the early 1990s (272 and 269 TgC, respectively). The estimates of mean C sink in live forest biomass also agreed well (0.36 and 0.34 Mg C ha^–1 yr^–1). Virtually all forest lands were accumulating C in live biomass, however when the net change in total ecosystem C stock was considered, 19% of the forest area were a net source of C. The average net C sink in total ecosystem biomass is quite weak (0.08 MgC ha^–1 yr^–1 and could be reversed by minor increases in harvest rates or a small decline in biomass growth rates.     

Can bottom-up procedures improve the performance of stream classifications?

Top-down methods for defining stream classifications are based on a conceptual model or expert-defined rules, whereas bottom-up methods use biological training data and statistical modelling. We compared the performance of six classification methods for explaining the taxonomic composition of invertebrate and fish assemblages recorded at 327 and 511 sites, respectively, distributed throughout France. Classification 1 and 2 were top-down classifications; The European Water Framework System A (WFDa,) and the French Hydro-ecoregions (HER 2). Four bottom-up classification procedures of increasing complexity were defined based on 11 variables that included watershed characteristics describing climate, topography, and geology, and site characteristics including elevation, bed slope and temperature. Classification 3 was defined using matrix correlation (MC) to select a combination of variable categories that produced the best discrimination of the observed taxonomic composition. Classification 4 and 5 were defined by clustering the sites based on their taxonomic data and then using linear discriminant analysis (LDA) and Random forests (RF) to discriminate the clusters based on the environmental variables. Classification 6 was defined using generalized dissimilarity modelling (GDM). Our hypothesis was that the bottom-up classifications would perform better because they flexibly accommodate complex relationships between compositional and environmental variation. We tested the classifications using the classification strength statistic (CS). The RF-based classification fitted the taxonomic patterns better than GDM or LDA and these latter classifications generally fitted better than the MC, WFDa or HER classifications. Cross validation analysis showed that differences in predictive CS (i.e. the CS statistics produced from sites not used in defining the classifications) were often significant. However, these differences were generally small. Gains in predictive performance of classifications appear to be small relative to the increase in complexity in the manner in which environmental variables are combined to define classes.