The impact of rural land management changes on soil hydraulic properties and runoff processes: results from experimental plots in upland UK

To develop an evidence base to help predict the impacts of land management change on flood generation, four experimental sites were established on improved grassland used for sheep grazing at the Pontbren catchment in upland Wales, UK. At each site, three plots were established where surface runoff was measured, supplemented by measurements of soil infiltration rates and soil and vegetation physical properties. Following baseline monitoring, treatments were applied to two of the plots: exclusion of sheep (ungrazed) and exclusion of sheep and planting with native broadleaf tree species (tree planted), with the third plot acting as a control (grazed pasture). Due to a particularly dry summer that occurred pre‐treatment, the soil hydrological responses were initially impacted by the effects of the climate on soil structure. Nevertheless, treatments did have a clear influence on soil hydrological response. On average, post‐treatment runoff volumes were reduced by 48% and 78% in ungrazed and tree‐planted plots relative to the control, although all results varied greatly over the sites. Five years following treatment application, near‐surface soil bulk density was reduced and median soil infiltration rates were 67 times greater in plots planted with trees compared to grazed pasture. The results illustrate the potential use of upland land management for ameliorating local‐scale flood generation but emphasise the need for long‐term monitoring to more clearly separate the effects of land management from those of climatic variability. Copyright © 2013 John Wiley & Sons, Ltd.     

PM2.5 co-benefits of climate change legislation part 2: California governor’s executive order S-3-05 applied to the transportation sector

California Governor’s Executive Order (CGEO) S-3-05 requires that California greenhouse gas (GHG) emissions be reduced to 80 % below 1990 levels by the year 2050. Meeting this target will require drastic changes in transportation technology, fuel, and behavior which will reduce criteria pollutant emissions as well as GHG emissions. The improvement to local air quality caused by the reduced criteria pollutant emissions must be calculated to fully evaluate the overall benefits and costs of CGEO S-3-05. In the present study, seven different transportation scenarios that move towards the goals of CGEO S-3-05 in the transportation sector were examined to determine how they would affect future airborne particulate matter (PM_2.5) concentrations in California: (1) hydrogen fuel cells, (2) electric vehicles, (3) high efficiency vehicles, (4) public mass transit, (5) biofuels, (6) biofuels + hybrid electric vehicles, and (7) hydrogen fuel cells + electric vehicles. The air quality implications of each scenario were evaluated using a chemical transport model applied during a wintertime stagnation episode representing future climate in California. Scenarios (6) and (7) reduced population-weighted PM_2.5 mass concentrations by ~9 % and PM_2.5 elemental carbon (EC) concentrations by ~30 % relative to base-case predictions.     

Optimizing fixed observational assets in a coastal observatory

Proliferation of coastal observatories necessitates an objective approach to managing of observational assets. In this article, we used our experience in the coastal observatory for the Columbia River estuary and plume to identify and address common problems in managing of fixed observational assets, such as salinity, temperature, and water level sensors attached to pilings and moorings. Specifically, we addressed the following problems: assessing the quality of an existing array, adding stations to an existing array, removing stations from an existing array, validating an array design, and targeting of an array toward data assimilation or monitoring.     

Lettau’s Contribution to the Obukhov Length Scale: A Scientific Historical Study

Boundary-Layer Meteorology - It has been repeatedly assumed that Heinz Lettau found the Obukhov length in 1949 independently of Obukhov in 1946. However, it was not the characteristic length scale,...     

The effect of tidal inlets on open coast storm surge hydrographs

Bridge scour modeling requires storm surge hydrographs as open ocean boundary conditions for coastal waters surrounding tidal inlets. These open coast storm surge hydrographs are used to accurately determine both horizontal and vertical circulation patterns, and thus scour, within the inlet and bay for an extreme event. At present, very little information is available on the effect that tidal inlets have on these open coast storm surge hydrographs. Furthermore, current modeling practice enforces a single design hydrograph along the open coast boundary for bridge scour models. This study expands on these concepts and provides a more fundamental understanding on both of these modeling areas.     

Prehistoric soil and water detention structures (gabarbands) at Phang,Sindh Kohistan,Pakistan: An adaptation to environmental change?

Five gabarbands (dams), components of integrated soil and water conservation systems, were investigated in the arid region of Sindh Kohistan. The dams are associated with two prehistoric Kot Dijian settlements, Phang and Kohtrash (3200–2800 B. C.). The dams were constructed with relatively permeable materials. Three of the dams, South, East, and North, close off water gaps and a strike valley, respectively, to form a detention basin. The West Dam, located on Phang Nai, upstream of the detention basin removed the coarser sediment fraction from the flows. Spring Dam, located in a water gap to the north of the detention basin, acted as a low-head weir to distribute flow from a perennial spring onto the floodplain of Baran Nai, where double-cropping was probably practiced. Faulting eliminated the spring, which had probably supported the Kohtrash site, and led to construction of the detection basin for the purposes of subsurface storage of detained flows. Association of both modern and prehistoric sites with springs suggests that there has not been appreciable climate change in Sindh Kohistan in the last 5000 years. © 1993 John Wiley & Sons, Inc.     

Modeling the natural degradation of earthworks

Stratigraphic, topographic, and ground‐penetrating radar data obtained from a ca. 1800‐year‐old embankment and adjacent ditch at the Hopewell Mound Group (Chillicothe, Ohio) are used to validate the archaeological application of a simple finite‐differences diffusion model employed frequently to assess geomorphic change in natural landscapes. Although diffusion models have been used to describe the topographic degradation of landforms in a variety of geomorphic terrains, the approach has not been applied to ancient earthworks in an archaeological context. The results of this study indicate that a variety of initial earthwork forms can result in the sinusoidal profile apparent on the current landscape. Using the model results to interpret the field data, we suggest that the initial embankment form was steeper and the adjacent ditch was deeper. As a result of natural degradation processes, the earthwork widened and flattened over time. These results have broad implications for any study aimed at: (1) assessing the function of original earthwork forms, (2) determining the formation processes of complicated stratigraphies or artifact assemblages, (3) estimating the time and labor investment required for construction, or (4) identifying the socio‐political structures necessary to build earthworks. © 2005 Wiley Periodicals, Inc.