For the last two years a second year overseas residential field course run by the School of Geography in the University of Manchester has been restructured into a Problem-based Learning format. This paper reports on the reasons for change, describes the structures and learning outcomes underpinning the PBL-based field experience and also addresses problems of implementing such a course. It is concluded that the potential of a student-centred and group-based approach to fieldwork can be realised if PBL is adopted as an organising framework for the whole learning experience.
<p>Flooding is costly and disruptive in the UK and worldwide. Leaky barriers (LBs), small-scale blockages to streamflow, provide multiple environmental benefits. Depending on design, and if installed in sufficient numbers, they could also play an important role in reducing downstream flooding. Leaky barrier installation is proceeding at pace, thousands of cobble dams have been installed in peat gullies across the South Pennines (UK). However, the hydraulics of LBs in general and these cobble barriers in particular is poorly understood. Here we develop a simple model coupling two classical engineering flux estimates: Darcy/Casagrande equations for matrix flow and Colebrook equation for pipe flow (where drains are installed). We test this model against observed stage and discharge measurements for four study features with and without drains to: identify stage-discharge relationships; evaluate model performance for individual features; and apply it to model chains of features of varying design (i.e., LB density, matrix permeability, and pipe diameter). We find that: 1) stage-discharge relationships for cobble dams are concave up and are generally well captured by our simple model; 2) current designs offer relatively little attenuation because they are too permeable; 3) instead, optimal designs have low matrix permeability with pass-forward pipes at their base of a diameter tuned to design flow. Based on these results we hypothesise that LBs will perform best where they are designed to have negative permeability-depth relationships (and thus convex up stage-discharge relationships) and where the form and magnitude of the relationship is optimised to accommodate peak flood discharges. &#160;</p>
<p>Microcatchments (<10 ha) are often used to monitor the effect of disturbances or restoration on the hydrological functioning of peatlands. Catchment areas serve as the spatial limits within which fluvial processes are studied and topographic parameters are derived. Digital Elevation Models (DEMs) and Digital Surface Models (DSMs) are used in standard practice to delineate the watershed boundary of microcatchments. These digital representations of topography contain errors, meaning the derived catchment areas have inherent uncertainty. The low-slope and hummock/hollow nature of peatland surfaces mean catchment delineation is particularly sensitive to vertical errors, so understanding the potential effect of uncertainty on the accuracy of catchment delineation is essential to providing a reliable account of peatland microcatchments hydrology.</p><p>This paper investigates the sensitivity of catchment delineation to DEM/DSM error for 30 peatland microcatchments across the Peak District National Park, UK. To evaluate the suitability of DSMs for hydrological applications in peatlands, a 0.25m photogrammetric DSM is used and evaluated against a 1m LiDAR DEM. Monte Carlo simulation is applied to produce a range of realisations of the DSM and DEM within their vertical error margins, from which a range of catchment areas are calculated. The variability of the watershed boundaries of each catchment is evaluated in the context of local gradient, difference from mean elevation and extent of gullying, to determine the relationship between terrain characteristics and variability in catchment delineation. Findings will have implications for the generation of catchment areas in peatland hydrology. &#160;</p>
<p>Before-after monitoring of small-scale restoration activities in blanket peatlands, e.g., revegetation and gully blocking, suggests they can also deliver significant Natural Flood Management (NFM) benefits (reduce and delay floodpeaks). However, we still lack a clear understanding of the underlying processes driving NFM effects; and doubts remain about whether interventions will retain their impact when implemented at scales large enough to reduce flooding in downstream communities. We examine the impact of the two interventions at a range of scales from the 1 hectare micro-catchment scale at which a Before-After-Control-Intervention (BACI) study has been undertaken, to the 40 km<sup>2</sup> scale (at which flooding begins to affect residential properties). We calibrate the Generalised Multistep Dynamic (GMD) TOPMODEL rainfall-runoff model to different BACI experimental catchments each representing an intervention scenario. Through numerical experimentation with the calibrated parameters, we estimate the impact-magnitude of different process drivers. Our findings confirm the NFM benefits of these restoration-focused interventions at the micro-catchment scale. In both interventions and in our largest storms, floodpeak attenuation is primarily due to roughness reducing the floodwave speed and thus thickening the overland flow (kinematic storage). More conventional, static storage (i.e. interception + ponding + evapotranspiration), becomes important only in smaller storms. Finally, we use the parameter-sets identified by calibrating to the BACI catchments to extend our findings to the 40 km<sup>2</sup> Glossop catchment. Glossop has experienced several damaging floods in the last 50 years and has received appreciable recent restoration activity. Here we use GMD-TOPMODEL in a second set of modelling experiments to estimate downstream impact of existing interventions and to examine the impact of alternative scenarios of spatially distributed intervention configurations.</p>
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