Keynote Speakers

We are pleased to announce the following Keynote Speakers for the conference, along with their talk titles and a short blurb on the topics they will present:

Prof. Mark Adams

University of Sydney, Sydney, Australia

“Bushfires and landscape management in Australia”

Bushfires in Australia, and wildfires elsewhere, are increasing in public prominence. Irrespective of their cause(s), high intensity fires in native vegetation cause major changes in the structure, chemistry and stability of surface soils. These changes contribute markedly to landscape patterns – in vegetation, in soil erosion, and in long-term ecosystem sustainability. In this talk I will use recent examples to outline the case for increasing efforts to manage wildfire risk and intensity and mitigate long-term costs.

Prof. David Airey

University of Sydney, New South Wales, Australia

" Bio-cementation for ground improvement"

Bio-cementation has been suggested as an environmentally safe method of ground improvement that makes use of in-situ soil and can avoid disruption to existing infrastructure. The concept is to use bacteria with suitable nutrients to precipitate cementing agents within the soil, a process known as microbially induced calcite precipitation (MICP). The most widely investigated approach has been to use the bacterium sporosarcina pasteurii in combination with urea and a calcium source to precipitate calcium carbonate. Several laboratory studies have confirmed that substantial increases in soil strength and stiffness are possible in sandy soils. The viability of the technique and the methods for creating bio-cementation in finer grained soils have received much less attention. The paper will provide a review of the bio-cementation process, discuss procedures for creating bio-cemented soil and discuss the strengths that can be achieved.

Pierre Raymond, Senior Site Rehabilitation Specialist

Terra Erosion Control Ltd., British Columbia, Canada

"Introduction of Design Guidelines for Erosion and Flood Control Projects for Streambank and Riparian Stability Restoration"

With the increasing demand for green technology and infrastructure within urban settings, there is an emerging need for designing engineers to have access to guidelines that blend soil bioengineering and civil engineering practices. This presentation will discuss how design guidelines developed for this purpose for the City of Calgary, Alberta, Canada are being applied successfully. Developed as a reference document for engineering consultants, the guidelines demonstrate how to incorporate soil bioengineering practices into conventional engineering for the protection of infrastructure, public places and high value riparian areas. These guidelines were originally developed with the objective of increasing the application and acceptance of vegetation- based prescriptions for urban riparian applications within the engineering community. Documentation of critical shear stress due to water flow and comparative resistance of material types are provided in the guidelines to assist in the selection of appropriate vegetation-based prescriptions. Since their initial distribution in 2012, the guidelines have been well received and successfully utilized. Engineering firms are using the guidelines to assist in the development of construction specifications included within tender documents to provide clear specifications to be followed by practitioners. A summary of the application monitoring results, adjustments to implementation and how a similar process could be adapted to different locations will also be discussed.

A/Prof Ian Rutherfurd

University of Melbourne, Melbourne, Australia

“Assumed resistance: the role of vegetation roots on the resistance of river banks to fluvial scour”

River banks erode by mass failure and by fluvial scour. The role of tree roots in strengthening river banks against mass failure is well established. Whilst managers almost universally assume that roots will dramatically reduce erosion by hydraulic forces (fluvial scour) this is not nearly as well studied. This paper reviews how tree roots increase the critical shear stress of river banks, and more importantly, how the roots reduce the erosion rate of those banks. The key literature on the topic comes from agricultural erosion, but also from the more recent experiments with hydraulic jets. We consider scaling relationships and potential limits to the effect of roots on fluvial scour, as well as how scour resistance declines over time once trees have died.

Dr Massimiliano Schwarz

Bern University of Applied Sciences, Bern, Switzerland

“Root reinforcement calculations: from single root to root system.”

Root reinforcement represents a key factor in different area of engineering (slope stability, soil protection, silviculture/tree stability, stability of river-banks). In this contribution we review some of the research done on root reinforcement quantification and we discuss the results in view of practical applications. Single factors involved in the calculations of root reinforcement are discussed within the framework of the Root Bundle Model and the application of a discrete element model for slope stability calculations.

Prof. Roy Sidle

University of Sunshine Coast, Queensland, Australia

“Effects of Vegetation Management on Slope Stability”

Vegetation, particularly woody vegetation, augments the stability of shallow soil mantles primarily by modifying the soil moisture regime through evapotranspiration and providing root reinforcement within the soil. Transpiration effects are not particularly important for shallow landslides that occur during an extended winter rainy season because soils are typically very wet and transpiration processes are reduced, but these effects may be important in the tropics and sub-tropics. Root reinforcement is generally regarded as a more important factor and management practices such as clear-cut timber harvesting and vegetation conversion for forests to agriculture or exotic plantations can significantly increase landslide potential in the period of about 3 to 15-20 years after vegetation removal.

Dr Andrew Simon

Cardno, Oxford, Mississippi, United States of America

“Role of Riparian Vegetation in Fluvial Geomorphology"

Riparian vegetation is a fundamental component of landscape systems. Its effects range across a broad spectrum of geomorphic processes and scales relating to the hydrologic cycle, water budgets, and soil moisture as well as resistance to overland and concentrated flows in channels and on flood plains. Most germane to this conference is the important role vegetation plays in streambank stability. The interaction and controls of riparian vegetation on fluvial processes can be separated into three general areas where it can often be regarded both as independent and dependent variables. These are: (1) hydraulic controls such as flow resistance, velocity and turbulence, (2) mechanical controls effecting initiation of motion (critical shear stress) and bank-failure processes by root reinforcement (shear strength), and (3) hydrologic controls on infiltration, evapotranspiration and pore-water pressure.

Riparian vegetation can exert strong, direct influences on erosion rates by providing greater resistance to hydraulic forces, reducing the effective stress acting on bank surfaces and enhancing geotechnical strength by root reinforcement. For these reasons, vegetation has become a major component in designing stream-rehabilitation measures. Riparian buffer strips made from native vegetation along stream channels reduce hydraulic shear and trap sediment. A by-product of this application is the reduction of pore-water pressures in streambanks through interception of precipitation and removal of water from the bank mass by evapotranspiration. Large woody debris is used in channels, often in meander bends to protect bank toes, induce deposition, and halt lateral migration. Aspects of the role of vegetation in controlling hydraulics, bank stability, sediment transport and channel adjustment have begun to be incorporated into quantitative analyses and numerical models of stream channels. Field and laboratory studies to quantify some of these important processes have led to advances in numerically accounting for vegetative effects and consequent fluvial processes. Examples of studies and application of numerical modelling tools such as the Bank-Stability and Toe-Erosion Model (BSTEM) will be provided.