Estimating the effects of water-induced shallow landslides on soil erosion

Rainfall induced landslides and soil erosion are part of a complex system of multiple interacting processes, and both are capable of significantly affecting sediment budgets. These sediment mass movements also have the potential to significantly impact on a broad network of ecosystems health, functionality and the services they provide. To support the integrated assessment of these processes it is necessary to develop reliable modelling architectures. This paper proposes a semi-quantitative integrated methodology for a robust assessment of soil erosion rates in data poor regions affected by landslide activity. It combines heuristic, empirical and probabilistic approaches. This proposed methodology is based on the geospatial semantic array programming paradigm and has been implemented on a catchment scale methodology using Geographic Information Systems (GIS) spatial analysis tools and GNU Octave. The integrated data-transformation model relies on a modular architecture, where the information flow among modules is constrained by semantic checks. In order to improve computational reproducibility, the geospatial data transformations implemented in ESRI ArcGis are made available in the free software GRASS GIS. The proposed modelling architecture is flexible enough for future transdisciplinary scenario analysis to be more easily designed. In particular, the architecture might contribute as a novel component to simplify future integrated analyses of the potential impact of wildfires or vegetation types and distributions, on sediment transport from water induced landslides and erosion.Comment: 14 pages, 4 figures, 1 table, published in IEEE Earthzine 2014 Vol. 7 Issue 2, 910137+ 2nd quarter theme. Geospatial Semantic Array Programming. Available: http://www.earthzine.org/?p=91013

Frost heave in compressible soils

We develop a mathematical model of frost heave in compressible soils based on a morphological instability of the ice–soil interface. The theory accounts for heave and soil consolidation,while avoiding the frozen fringe assumption. Using a Lie-B¨acklund transformation an analytical solution to the governing equations is found. Two solidification regimes occur: a compaction regime in which the soil consolidates to accommodate the ice lenses, and a heave regime during which the soil is fully consolidated and heaves. The rate of heave is found to be independent of the rate of freezing, consistent with field and laboratory observations

Pseudospectral methods provide fast and accurate solutions for the horizontal infiltration equation

An extremely fast and accurate pseudospectral numerical method is presented, which can be used in inverse methods for estimating soil hydraulic parameters from horizontal infiltration or desorption experiments. Chebyshev polynomial dierentiation in conjunction with the flux concentration formulation of Philip (1973) results in a numerical solution of high order accuracy that is directly dependent on the number of Chebyshev nodes used. The level of accuracy (< 0:01% for 100 nodes) is confirmed through a comparison with two dierent, but numerically demanding, exact closed-form solutions where an infinite derivative occurs at either the wetting front or the soil surface. Application of our computationally ecient method to estimate soil hydraulic parameters is found to take less than one second using modest laptop computer resources. The pseudospectral method can also be applied to evaluate analytical approximations, and in particular, those of Parlange and Braddock (1980) and Parlange et al (1994) are chosen. It is shown that both these approximations produce excellent estimates of both the sorptivity and moisture profile across a wide range of initial and boundary conditions and numerous physically realistic diusivity functions

The full circle: enhancing feedback to students

At Loughborough University, the School of Civil and Building Engineering commissioned the Centre for Engineering and Design Education to undertake a longitudinal study, over four years, to explore issues associated with feedback on assignments from both the staff and student perspective. This study was prompted by low feedback scores on the National Student Survey* and initially explored the sources of students’ dissatisfaction with feedback and their perceptions of what constitutes feedback. In later years the study was broadened to explore how students use their feedback and the impediments to this. The findings of the study have influenced the feedback strategy and practice within the School with clear guidance given to staff, training provided to students and the introduction of enhanced feedback quality monitoring processes. This paper reports on the fourth year of the study, which goes full circle back to students’ perception of effective feedback. The fourth year of the study seeks to explore, from the student perspective, whether the changes made have addressed the original issues raised by the students, whether they are satisfied with the quality of the feedback they now get and whether their expectations regarding feedback have changed. The study uses a combination of focus group discussions, and questionnaires to gather data from second and third year students who have been impacted most by the feedback changes made within the School. This paper shares key findings from the study, including the impact that the practice changes have had on the general students’ understanding of feedback and the changes in level of expectation of feedback, particularly with respect to the most engaged students

Developing the critical thinking skills of students in Civil and Building Engineering at Loughborough University.

This research investigated the critical thinking skills of undergraduate students in Civil and Building Engineering (CBE) at Loughborough University. In particular it focused on individual students’ perceptions of what critical thinking entailed, the views of staff regarding the students’ ability in this area, especially relating to final year research projects, and modules where critical thinking skills were addressed and assessed. The attitude to critical thinking by students from different cultures and countries was also examined. There are seven different programmes within CBE and differences in student ability and module content were compared and contrasted between programmes, with particular focus on modules studied during the first two years at university. The focus on modules prior to the final year of study was a result of Programme Directors and Project Supervisors reporting that students are not adequately demonstrating critical thinking skills when undertaking research-based tasks in their final year of study. A questionnaire, which was designed to gain an insight into students’ understanding of critical thinking, was completed by 39 students from five different programmes of study. In addition to preliminary discussions with all Programme Directors in the School, ten academic members of staff were interviewed to determine their views on the level of critical thinking demonstrated by the students and their own level of focus on this skill in their teaching. The findings from the questionnaires and interviews were then related to the modules of study for these programmes and a map detailing gaps in exposing students to this skill were produced. The findings show that from the student perspective the majority of those surveyed do understand what critical thinking involves and believe this to be important to their future working lives. However, from the staff perspective it appears that, in the main, students do not demonstrate aspects of critical thinking unless explicitly asked to do so and students who do demonstrate critical thinking, for example, when undertaking research projects do not do it at the level that is expected. If students are to view critical thinking as an important part of their development then it is essential that these skills are assessed in more modules. This will ensure that students enter the workplace with the ability to analyse situations, challenge the views of others and make informed decisions

Quantifying the heterogeneity of soil compaction, physical soil properties and soil moisture across multiple spatial scales [Abstract]

Quantifying the heterogeneity of soil compaction, physical soil properties and soil moisture across multiple spatial scales [Abstract

Revisiting Salvucci’s Semi-analytical Solution for Bare Soil Evaporation with New Consideration of Vapour Diffusion and Film Flow

Bare soil evaporation is controlled by a combination of capillary flow, vapour diffusion and film flow. Relevant analytical solutions mostly assume horizontal flow conditions and ignore gravitational effects. Salvucci (1997) provided a rare example of a semi-analytical solution for vertical bare soil evaporation. However, they did not explicitly represent vapour diffusion and film flow, which are likely to account for a significant proportion of total flow during vertical evaporation from soils. Vapour diffusion and film flow can be incorporated via Salvucci’s desorptivity parameter, which represents the proportionality constant relating Stage 2 cumulative evaporation to the square root of time under horizontal flow conditions. The objective of this article is to implement vapour diffusion and film flow within Salvucci’s semi-analytical solution and test its performance by comparison with isothermal numerical simulation and relevant experimental data. The following important conclusions are drawn. Analytical solutions that assume horizontal flow conditions are inadequate for understanding vertical evaporation problems because they overestimate evaporation rates and mostly predict vapour diffusion and film flow to be of negligible influence. Salvucci’s semi-analytical solution is effective at predicting the order-of-magnitude reduction in evaporation caused by gravitational effects. However, it is unable to identify the correct importance of vapour diffusion and film flow because these processes can only be represented through its desorptivity parameter

Modeling overland flow and soil erosion on nonuniform hillslopes: a finite volume scheme.

This paper presents a finite volume scheme for coupling the St. Venant equations with the multi- particle size class Hairsine-Rose soil erosion model. A well-balanced MUSCL-Hancock scheme is proposed to minimize spurious waves in the solution arising from an imbalance between the flux gradient and the source terms in the momentum equation. Additional criteria for numerical stability when dealing with very shallow flows and wet-dry fronts are highlighted. Numerical tests show that the scheme performs well in terms of accuracy and robustness for both the water and sediment transport equations. The proposed scheme facilitates the application of the Hairsine-Rose model to complex scenarios of soil erosion with concurrent interacting erosion processes over a non-uniform topography