Continuous prediction of clay‐bed stream erosion in response to climate model output for a small urban watershed

The response of the semi‐alluvial clay‐bed Watts Creek is assessed subject to climate change. Climate impacts are expected to have regional variability, and few studies have assessed the impacts of future climate in a small urban watershed. The 21‐km² watershed located in Ottawa, Ontario, Canada, is highly urbanized (68%) and agricultural (20%) with limited forest cover (12%). Continuous simulations were performed using the SWMHYMO lumped hydrologic modelling platform for the open water year, excluding spring freshet (April 1 to October 31). A shear stress exceedance and stream power erosion routine was added to the platform to calculate erosion potential. To account for uncertainty in the collected data, 9 different field datasets were used to calibrate the model, each leading to a distinct set of calibrated parameter values. The difference between the datasets lies in the choice of the rating curves and calibration period. The 2041–2080 precipitation outputs of the 4th version of the Canadian Regional Climate Model (CanRCM4) ran under representative concentration pathways (RCPs) 4.5 and 8.5 at the MacDonald Cartier International Airport were downscaled using quantile matching and then used as input to the continuous hydrologic model. For each set of calibrated parameters, a cumulative effective work index based on the reach‐averaged shear stress was calculated for Watts Creek using both the historic (1967–2007) and projected future (2041–2080) flows, using a bed material critical shear stress for entrainment of 3.7 Pa. These results suggest an increase of 75% (respectively 139%) under RCP4.5 (respectively RCP8.5) in cumulative effective work index compared with historic conditions for the average measured bed strength. The work index increase is driven by an increased occurrence of above‐threshold events and, more importantly, by the increased frequency of large events. The predicted flow regime under climate change would significantly alter the erosion potential and stability of Watts Creek.     

The case for support of manned spaceflight as a platform for research on sarcopenia and osteopenia

The United Kingdom government has decided to be part of the European Space Agency’s Aurora programme, but so far it has declared an intention only to participate in aspects of the programme which do not involve human space flight. Personally, we believe this to be a mistake, mainly because of the inherent limitations of robots, especially in unforeseen circumstances. However the arguments we make are different to this and are focussed mainly upon the benefits to earth based science, medicine, technology and education which would accrue from a manned space flight programme.     

Geomorphological effectiveness of floods to rework gravel bars: Insight from hyperscale topography and hydraulic modelling

Bars are key morphological units in river systems, fashioning the sediment regime and bedload transport processes within a reach. Reworking of these features underpins channel adjustment at larger scales, thereby acting as a key determinant of channel stability. Despite their importance to channel evolution, few investigations have acquired spatially continuous data on bar morphology and sediment-size to investigate bar reworking. To this end, four bars along a 10 km reach of a wandering gravel-bed river were surveyed with terrestrial laser scanning (TLS), comparing downstream changes in slope, bed material size and channel planform. Detrended standard deviations (σ_z) were extracted from TLS point clouds and correlated to underlying physically measured median grain-size (D₅₀), across a greater range of σ_z values than have hitherto been reported. The resulting linear regression model was used to create a 1 m resolution median grain-size map. A fusion of airborne LiDAR and optical-empirical bathymetric mapping was used to develop reach-scale digital elevation models (DEMs) for rapid two-dimensional hydraulic modelling using JFlow® software. The ratio of dimensionless shear stress over critical shear stress was calculated for each raster cell to calculate the effectiveness of a range of flood events (2.33–100 year recurrence intervals) to entrain sediment and rework bar units. Results show that multiple bar forming discharges exist, whereby frequent flood flows rework tail and back channel areas, while much larger, less frequent floods are required to mobilise the coarser sediment fraction on bar heads. Valley confinement is shown to exert a primary influence on patterns of bar reworking. Historical aerial photography, hyperscale DEMs and hydraulic modelling are used to explain channel adjustment at the reach scale. The proportion of the bar comprised of more frequently entrained units (tail, back channel, supra-platform) relative to more static units (bar head) exerts a direct influence upon geomorphic sensitivity. © 2018 John Wiley & Sons, Ltd.     

The TAP III beamforming system

The Three-Array Processor (TAP III) beamforming system incorporating both wide-band time-domain beamforming and narrow-band frequency-domain beamforming is described. This paper briefly develops the beamforming theory and shows how the fast Fourier transform (FFT) is applied to accomplish frequency-domain beamforming. The frequency-domain beamformer operates in the frequency domain to form beams and power spectrum data over narrow frequency bands of interest. A real-time digital filtering technique is used to extract the narrow bands of interest from the broad-band input signal. The frequency-domain beamformer accomplishes real-time digital filtering and beamforming by using a high-speed array processor to do the complex calculations and data handling required by the algorithm. The time-domain beamformer operates in parallel with the frequency-domain beamformer to form up to 16 broad-band beams in the time domain. A programmable all-pass digital filter is used to create the fine time delays required by the time-domain beamformer.     

The disturbing case of the concentration of power in human geography

The increasing concentration of power in academic disciplines with the introduction of Research Assessment Exercises is noted. The case of human geography in the UK is discussed.     

High resolution provenancing of long travelled dust deposited on the Southern Alps, New Zealand

On 7 February 2000 an atypical orange discolouration of snowfields in the central Southern Alps, New Zealand occurred following the passage of a cold front. Analysis of snow samples identified fine orangey-brown dust mixed with much coarser grey dust. Air parcel forward trajectories from dust sources in southern and central Australia, where dust storms were reported on 4 February 2000, were computed to identify the deposits source. Geochemical analyses of the dust deposit using 26 trace elements, unaffected by regional air pollution and gravitational sorting, indicate that 20% of the dust was sourced from western New South Wales, with 45% from the eastern Eyre Peninsula of South Australia and the remaining 35% was local New Zealand dust. This provenancing approach provides a spatial resolution of long travelled dust sourcing not previously achieved.