Isaac Greene, Weena Lokuge and Warna Karunasena
Current methods for floodway design are predominately based on hydrological and hydraulic design principles. The purpose of this paper is to investigate a finite element methods…
Abstract
Purpose
Current methods for floodway design are predominately based on hydrological and hydraulic design principles. The purpose of this paper is to investigate a finite element methods approach for the inclusion of a simplified structural design method into floodway design procedures.
Design/methodology/approach
This research uses a three-dimensional finite element method to investigate numerically the different parameters, geometric configurations and loading combinations which cause floodway vulnerability during extreme flood events. The worst-case loading scenario is then used as the basis for design from which several structural design charts are deduced. These charts enable design bending moments and shear forces to be extracted and the cross-sectional area of steel and concrete to be designed in accordance with the relevant design codes for strength, serviceability and durability.
Findings
It was discovered that the analysed floodway structure is most vulnerable when impacted by a 4-tonne boulder, a 900 mm cut-off wall depth and with no downstream rock protection. Design charts were created, forming a simplified structural design process to strengthen the current hydraulic design approach provided in current floodway design guidelines. This developed procedure is demonstrated through application with an example floodway structural design.
Originality/value
The deduced structural design process will ensure floodway structures have adequate structural resilience, aiding in reduced maintenance and periods of unserviceability in the wake of extreme flood events.
Details
Keywords
Buddhi Wahalathantri, Weena Lokuge, Warna Karunasena and Sujeeva Setunge
The 2011 and 2013 Queensland, Australia flood events caused massive infrastructure damage for low-level stream crossings such as floodways and culverts in regional Queensland…
Abstract
Purpose
The 2011 and 2013 Queensland, Australia flood events caused massive infrastructure damage for low-level stream crossings such as floodways and culverts in regional Queensland. Failures of newly built floodways during the 2013 Queensland flood event in the Lockyer Valley Regional Council area raised significant concerns with respect to floodway design practices adopted in Australia and attracted significant research interest to enhance the resilience of floodways. Review of existing floodway design guidelines indicates that floodway design process is closely related to hydraulic and hydrological aspects. However, conducting a hydrological analysis is a challenging in rural areas, mainly owing to information scarcity. Floodways in rural areas often require a simple and economical solution contrast to more detailed hydrological analysis approaches adopted in urbanised areas. This paper aims to identify and apply the rational method to estimate maximum flood discharges at selected floodway locations in the Lockyer Valley Regional Council area. The paper further attempts to provide the first insight of flood characteristics during the 2011 and 2013 Queensland flood events at three catchment outputs across the selected case study area. It also highlights modern day challenges for practising engineers and researchers when estimating flood characteristics in rural areas. The paper shows that cross-cultivation of advancement in engineering practices and traditional approaches can promote quantitative approaches when assessing floodway damage in regional areas.
Design/methodology/approach
The research identifies limitations when assessing flood impact in rural regions in collaboration with experience from industry partners and authors themselves. The authors developed a framework to overcome those limitations arising from information scarcity to minimise the trial and error design approaches utilised in the current design practices for floodways.
Findings
This paper developed a simple and effective hydrological method with minimum inputs. It also provides an example on collating available but scattered resources and traditional method to quantitatively assess flood discharges of a rural catchment in Australia. Flood discharges at three catchment outlets along the Left-Hand Branch Road in the Lockyer Valley Region during both 2011 and 2013 Queensland flood events are estimated for the first time. The findings highlight the impact of flood discharges and flooded period on floodway failures.
Research limitations/implications
The current research is based on a selected case study area in Australia. However, similar challenges are expected all across the world, due to the scarcity of rainfall and flood measurement gauges.
Practical implications
Floodway designers can apply similar framework to estimate the flood discharges instead of current practice of trial and error process. This will provide more scientific and reliable estimation and assessment process.
Social implications
One of the social impacts identified in the broader research is the community outrages and disagreement between floodway design engineers and the community. Following the developed framework in the manuscript, design engineers will be able to justify their assumptions and design work.
Originality/value
The paper presents a novel framework on collating different and scattered information towards estimating flood discharges in rural areas. The manuscript presents the first insights on estimated flood discharges in the selected case study area during the 2011 and 2013 Queensland flood events. This will enable further research to be performed in a quantitative manner rather than the present approach of qualitative manner.
Details
Keywords
Nam Mai-Duy, Cam Minh Tri Tien, Dmitry Strunin and Warna Karunasena
The purpose of this paper is to present a new discretisation scheme, based on equation-coupled approach and high-order five-point integrated radial basis function (IRBF…
Abstract
Purpose
The purpose of this paper is to present a new discretisation scheme, based on equation-coupled approach and high-order five-point integrated radial basis function (IRBF) approximations, for solving the first biharmonic equation, and its applications in fluid dynamics.
Design/methodology/approach
The first biharmonic equation, which can be defined in a rectangular or non-rectangular domain, is replaced by two Poisson equations. The field variables are approximated on overlapping local regions of only five grid points, where the IRBF approximations are constructed to include nodal values of not only the field variables but also their second-order derivatives and higher-order ones along the grid lines. In computing the Dirichlet boundary condition for an intermediate variable, the integration constants are used to incorporate the boundary values of the first-order derivative into the boundary IRBF approximation.
Findings
These proposed IRBF approximations on the stencil and on the boundary enable the boundary values of the derivative to be exactly imposed, and the IRBF solution to be much more accurate and not influenced much by the RBF width. The error is reduced at a rate that is much greater than four. In fluid dynamics applications, the method is able to capture well the structure of steady highly non-linear fluid flows using relatively coarse grids.
Originality/value
The main contribution of this study lies in the development of an effective high-order five-point stencil based on IRBFs for solving the first biharmonic equation in a coupled set of two Poisson equations. A fast rate of convergence (up to 11) is achieved.