Dr Hannah Power
School of Environmental and Life Sciences (Earth Sciences)
- Phone:(02) 4921 5606
Drawing a line in the sand
The research of Dr Hannah Power, a recent finalist in the national search for the 2015 ASPIRE science prize, focuses primarily on the study of coastal processes and the geomorphology of sandy beaches.
THE SANDS OF TIME
The focal point of Dr Hannah Power's research is ocean waves, how they behave, and how they affect the movement of sediment.
This work underpins the effective management of sustainable coastal environments, through predicting beach erosion, and anticipating how beaches change with time.
Understanding how waves behave creates the capacity to model how water will act during both calm periods and major weather events such as tsunamis and storms.
In late 2014, Hannah, a lecturer in the School of Environmental and Life Sciences, received a grant from the NSW Ministry for Police and Emergency Services to undertake modeling related to tsunami attenuation in coastal waterways.
It is also her work in this area of coastal hazard risk reduction that saw Hannah chosen as one of the final three nominees in the search to identify Australia's best representative for the APEC Science Prize for Innovation, Research and Education (also known as the ASPIRE Prize).
TAKING A DIVE
Growing up in Sydney, with frequent holidays on the south coast of NSW, Hannah spent endless summer days swimming and body surfing.
It was learning to scuba dive on the Great Barrier Reef at age 14, however, which cemented her future.
"I always had an interest in science, but all of a sudden I became really interested in marine biology and marine ecology," Hannah recalls.
"So I enrolled in a marine science degree at the University of Sydney. In my second year I discovered that I really liked the numerical aspects of oceanography, more than I liked biology."
"I did intend to end up a marine scientist, but have ended up at the other end of the spectrum."
Hannah then completed her PhD with the Coastal Engineering Research Group at the University of Queensland, focusing on coastal processes. She came to Newcastle in 2013 after a stint working for the Government.
"I like that in the work I do now, things can be quantified for most part. Everything can be described and predicted numerically and that appeals to my personality," Hannah asserts.
ON THE CREST OF THE WAVE
It is the underlying physical processes, and how they affect our beaches, that informs the modeling capable of predicting long-term scale change.
"The modeling works by simulating as many of the processes and their complex interactions that we understand to predict the outcome of those processes and interactions over long time scales," Hannah explains.
Identifying the factors that lead to large runup events on a wave-by-wave basis is a current area of focus for Hannah.
Traditionally, wave process and modeling have been looked at from a time averaged perspective, which has its benefits but also limits.
In early 2015, Hannah made a major contribution to an emerging direction in her field by publishing a paper describing a new method of tracking an individual wave across a beach. This previously undeveloped method allows researchers to measure how a single wave evolves through time or, in other words, how it moves onto the beach.
Hannah has identified that a major hurdle to effective modeling of wave behaviour is a general lack of understanding of how waves behave on an individual, wave-by-wave basis.
CASTLES MADE OF SAND
Another core area in Hannah's research relates to the efficacy of coastal management systems through investigating the movement of sediment.
Hannah explains that beaches are dynamic systems, constantly changing and undergoing natural cycles of erosion and accretion, which can be clearly seen in South Eastern Australia. Sand shifts offshore in large storms but is returned over time in a system that generally has a net equilibrium.
Historically, planning decisions for building along the coastline have sometimes been made without the information and numerical models that we have today.
Hannah points to areas such as Old Bar, Jimmy's Beach and Collaroy-Narrabeen Beach as examples of sites where buildings are now being affected by coastal erosion.
Sand nourishment projects, the building of rock revetment structures and councils securing at risk properties are all expensive actions invoked as short term salves to limit the danger to lives and assets posed by erosion cycles.
Having previously studied the movement of sediment on coral reefs, and what forcing conditions created that motion, Hannah is looking to invest more time researching this aspect and its implications in other coastal systems.
WE'RE GOING TO NEED A BIGGER BOAT
It is her advanced modeling capabilities and expertise around coastal hazards that saw Hannah recently receive a grant to advise the NSW Police and Emergency Services on their tsunami evacuation plan.
Focusing specifically on inundation in rivers, harbours and estuaries, Hannah will use mathematical modeling to predict how the shape of the coastline and waterways will affect the attenuation of the wave as it propagates upstream.
Predicting how far inland a large wave could travel along existing waterways will inform how far upstream an evacuation plan would need to be activated.
"For example," Hannah explains, "in the Hunter River, we still see the signal from the ocean tide up at Maitland. But for a small tsunami, we don't currently know how far up we would need to evacuate."
"My project aims to fill this knowledge gap."
BACK TO THE BEACH
A passionate educator, Hannah currently teaches students across several faculties how to map data of a spatial nature through a Geographical Information Systems course. Pending approval from the faculty teaching committee, a new Coastal Environments and Processes course would begin in 2016.
The course, which would include a fieldwork component to be undertaken in the Pacific Palms region, would teach students about coastal systems, from beaches, to rocky coastlines, to muddy coastlines, through to coral reefs.
Hannah is typically understated in her assertion, "I think there will be reasonably high interest levels."
And before you ask, no, she doesn't surf.
"When I tell people I'm an academic, I teach at the university and I do research on beaches and waves, the question I tend to get asked is 'Do you surf?'"
She doesn't need to surf for recreation because her office is already at the beach, to the envy of many.
"When I was doing my honours degree I thought if I can get paid to go to the beach as a career, I have done well," she confesses.
"Last year I spent four weeks at the beach doing fieldwork, and I thought that was pretty good."
Dr Hannah Power is a lecturer and coastal scientist in the Environmental and Climate Change Research Group (ECCRG) within the School of Environmental and Life Sciences. Hannah's primary research focuses on the study of coastal processes and geomorphology of sandy beaches. Of particular interest to Hannah are the hydrodynamics of waves after breaking and the implications this has for sediment transport and swash zone processes. Hannah's interests also extend to the processes and geomorphology of coral reef systems as well as beach erosion and coastal hazards such as storm surge and tsunami. Hannah has experience in coastal hydrodynamics, coastal and reef geomorphology, sediment transport, hydrodynamic modelling, statistical analysis, computer programming, remote sensing, and GIS/spatial analysis.Research Expertise
- Coastal processes and geomorphology - Nearshore hydrodynamics and hydrodynamic modelling - Nearshore sediment transport - Geophysical signal processing - Image analysis - Parametric modelling - Geographic Information Systems - Oceanographic sampling equipment - Field experiments (design and implementation) in the coastal zone
- Doctor of Philosophy, University of Queensland
- Bachelor of Science (Marine Science)(Honours), University of Sydney
- Coastal hazards
- Coastal processes
- Geographic Information Systems (GIS)
- Remote sensing
- Sediment transport
Fields of Research
|040699||Physical Geography and Environmental Geoscience not elsewhere classified||40|
|090599||Civil Engineering not elsewhere classified||30|
|Title||Organisation / Department|
|Senior Lecturer||University of Newcastle
School of Environmental and Life Sciences
For publications that are currently unpublished or in-press, details are shown in italics.
Journal article (37 outputs)
Mollison KC, Power HE, Clarke SL, Baxter AT, Hubble TCT, 'Sedimentology, structure, and age of the Wide Bay Canyon submarine landslide on the southeast Australian continental slope', Marine Geology, 419 (2020) [C1]
Wilson KM, Power HE, 'Tsunami Modelling with Static and Dynamic Tides in Drowned River Valleys with Morphological Constrictions', PURE AND APPLIED GEOPHYSICS, (2020)
Power HE, Gharabaghi B, Bonakdari H, Robertson B, Atkinson AL, Baldock TE, 'Prediction of wave runup on beaches using Gene-Expression Programming and empirical relationships', Coastal Engineering, 144 47-61 (2019) [C1]
Stringari CE, Harris DL, Power HE, 'A novel machine learning algorithm for tracking remotely sensed waves in the surf zone', Coastal Engineering, 147 149-158 (2019) [C1]
Stringari CE, Power HE, 'The Fraction of Broken Waves in Natural Surf Zones', JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 124 9114-9140 (2019)
Helfensdorfer AM, Power HE, Hubble TCT, 'Modelling Holocene analogues of coastal plain estuaries reveals the magnitude of sea-level threat', SCIENTIFIC REPORTS, 9 (2019) [C1]
Greenslade DJM, Uslu B, Allen SCR, Kain CL, Wilson KM, Power HE, 'Evaluation of Australian Tsunami Warning Thresholds Using Inundation Modelling', PURE AND APPLIED GEOPHYSICS, (2019)
Power HE, Clarke SL, '3D seismic-derived bathymetry: a quantitative comparison with multibeam data', Geo-Marine Letters, 39 447-467 (2019) [C1]
Power HE, Kinsela MA, Stringari CE, Kendall MJ, Morris BD, Hanslow DJ, 'Automated Sensing of Wave Inundation across a Rocky Shore Platform Using a Low-Cost Camera System', REMOTE SENSING, 10 (2018) [C1]
Wilson KM, Power HE, 'Seamless bathymetry and topography datasets for New South Wales, Australia', SCIENTIFIC DATA, 5 (2018) [C1]
Harris DL, Power HE, Kinsela MA, Webster JM, Vila-Concejo A, 'Variability of depth-limited waves in coral reef surf zones', Estuarine, Coastal and Shelf Science, 211 36-44 (2018) [C1]
Harris DL, Rovere A, Casella E, Power H, Canavesio R, Collin A, et al., 'Coral reef structural complexity provides important coastal protection from waves under rising sea levels.', Science Advances, 4 (2018) [C1]
Martins K, Blenkinsopp CE, Deigaard R, Power HE, 'Energy Dissipation in the Inner Surf Zone: New Insights From LiDAR-Based Roller Geometry Measurements', JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 123 3386-3407 (2018) [C1]
Vila-Concejo A, Gallop SL, Hamylton SM, Esteves LS, Bryan KR, Delgado-Fernandez I, et al., 'Steps to improve gender diversity in coastal geoscience and engineering', Palgrave Communications, 4 1-9 (2018) [C1]
Wilson KM, Allen SCR, Power HE, 'The Tsunami Threat to Sydney Harbour, Australia: Modelling potential and historic events', SCIENTIFIC REPORTS, 8 (2018) [C1]
Robertson B, Gharabaghi B, Power HE, 'Predicting Breaking Wave Conditions Using Gene Expression Programming', COASTAL ENGINEERING JOURNAL, 59 (2017) [C1]
Atkinson AL, Power HE, Moura T, Hammond T, Callaghan DP, Baldock TE, 'Assessment of runup predictions by empirical models on non-truncated beaches on the south-east Australian coast', COASTAL ENGINEERING, 119 15-31 (2017) [C1]
Martins K, Blenkinsopp CE, Power HE, Bruder B, Puleo JA, Bergsma EWJ, 'High-resolution monitoring of wave transformation in the surf zone using a LiDAR scanner array', Coastal Engineering, 128 37-43 (2017) [C1]
© 2017 Understanding of breaking and broken waves is key for the prediction of nearshore sediment transport and coastal hazards, however the difficulty of obtaining measurements o... [more]
© 2017 Understanding of breaking and broken waves is key for the prediction of nearshore sediment transport and coastal hazards, however the difficulty of obtaining measurements of highly unsteady nearshore waves has limited the availability of field data. This paper reports on a novel field experiment designed to capture the time-varying free-surface throughout the surf and swash zones was conducted on a dissipative sandy beach using an array of 2D LiDAR scanners. Three scanners were deployed from the pier at Saltburn-by-the-Sea, UK for a 6 day period to monitor the surface elevation of nearshore waves from the break point to the runup limit at temporal and spatial resolutions (order of centimetres) rarely achieved in field conditions. The experimental setup and the procedure to obtain a continuous time series of surface elevation and wave geometry is described. A new method to accurately determine the break point location is presented and compared to existing methodologies.
Power HE, Nielsen P, Hughes MG, Aagaard T, Baldock TE, 'Wave Height Distributions in the Surf Zone on Natural Beaches', JOURNAL OF COASTAL RESEARCH, 917-921 (2016) [C1]
Wilson OA, Power HE, 'Tsunami Inundation Modelling in Estuaries: Sensitivity to Variation in Tide from an Emergency Management Perspective', JOURNAL OF COASTAL RESEARCH, 1262-1266 (2016) [C1]
Van Leeuwen BR, McCarroll RJ, Brander RW, Turner IL, Power HE, Bradstreet AJ, 'Examining rip current escape strategies in non-traditional beach morphologies', Natural Hazards, 81 145-165 (2016) [C1]
© 2015, Springer Science+Business Media Dordrecht. Rip currents are a significant hazard on global surf beaches and are a factor in hundreds of drowning fatalities each year. Cont... [more]
© 2015, Springer Science+Business Media Dordrecht. Rip currents are a significant hazard on global surf beaches and are a factor in hundreds of drowning fatalities each year. Contemporary rip current safety information often idealises rip currents as part of a Transverse Bar Rip (TBR) morphology with rip channels bound by shallow, shore-connected bars. Real-world conditions frequently differ from this model, with potential implications for rip current escape strategies promoted to, and undertaken by, the general public. This study describes outcomes of rip current escape strategies conducted at North Cronulla Beach, NSW, Australia, over two distinct morphologies; a mixed Low Tide Terrace/Transverse Bar Rip (LTT/TBR) and a Rhythmic Bar Beach (RBB) system lacking shore-connected bars. Swimmers attempted to escape by adopting one of three pre-determined strategies: Stay Afloat, Swim Parallel and Swim Onshore. A total of 100 escape attempts were conducted, with the RBB system experiencing longer duration (t¯¿=¿2.4¿min) escapes than the LTT system (t¯¿=¿0.8¿min). The RBB system was associated with a higher rate of action failure, particularly for Stay Afloat, due to a lack of shore connectivity of adjacent bars. Swim Parallel was of lower duration (t¯RIP1¿=¿0.66, t¯RIP2¿=¿2.68¿min) in both systems, but durations and distances to safety in the RBB system often exceeded swimming abilities of weaker bathers. Although Swim Onshore was more successful (t¯RIP1¿=¿0.22, t¯RIP2¿=¿1.65¿min) than Swim Parallel, promotion of such a strategy is strongly discouraged in conventional safety advice. Results suggest that contemporary rip current escape strategies may be inappropriate in non-TBR rip current systems and that alternative strategies should be considered, including Swim Onshore and a greater focus on preventative strategies, particularly in relation to bathers with limited swimming ability.
Harris DL, Vila-Concejo A, Webster JM, Power HE, 'Spatial variations in wave transformation and sediment entrainment on a coral reef sand apron', Marine Geology, 363 220-229 (2015) [C1]
© 2015 Elsevier B.V. Waves are the main hydrodynamic force acting on coral reefs and are crucial in driving the evolution of reef systems. Previous research has mainly focused on ... [more]
© 2015 Elsevier B.V. Waves are the main hydrodynamic force acting on coral reefs and are crucial in driving the evolution of reef systems. Previous research has mainly focused on wave breaking and transformation on the reef flat but often neglected the spatial variation of reformed wave characteristics once they have propagated into the back-reef environment. This study examines wave conditions on a reef flat and the adjacent back-reef sand apron specifically focusing on the transformation of wave height, period and spectra (including changes to long-period and incident wave height). The ability of reformed waves in the back-reef environment to entrain sediment is also investigated. Wave conditions were found to be distinctly different on the sand apron compared to the reef flat, with the majority of wave energy dissipated during initial breaking and transformation. Almost all incident waves are dissipated on the reef flat under a depth threshold of 0.5. m before reaching the back-reef with long-period motions dominating in the back-reef during these tidal stages. At higher tidal stages incident waves are capable of propagating into the back reef but they are very low energy with under 1% of all waves capable of entraining sediment. This suggests that higher energy events, such as high frequency storms, are required to significantly transport sediment and change reef geomorphology. Smaller scale spatial changes in wave height were observed on the sand apron that shows the influence of both cross- and along-reef attenuation processes. A distance parameter (Xpd) is introduced that combines the cross-reef distance from the reef crest (Xd) and the temporally specific along-reef distance from the first point of wave breaking on the reef rim (Xp, where Xpd=. Xd+. Xp). Xpd is shown to accurately describe the changes in wave height and sediment entrainment if deep water significant wave height, wave direction, and depth over the reef flat are known. The results in this study shows that wave conditions, sediment entrainment, and longer term trends in sediment characteristics can be predicted in back-reef environments from a few simple geomorphic inputs.
Power HE, Hughes MG, Baldock TE, 'A novel method for tracking individual waves in the surf zone', Coastal Engineering, 98 26-30 (2015) [C1]
© 2015 Elsevier B.V. A new method to obtain information on individual waves as they travel shoreward is described. The wave-tracking method involves analysis of synchronous water ... [more]
© 2015 Elsevier B.V. A new method to obtain information on individual waves as they travel shoreward is described. The wave-tracking method involves analysis of synchronous water level records obtained from a shore-normal transect of pressure transducers (PTs). The method is illustrated here using data from field deployments inside the surf zone, although the method could equally be applied outside the surf zone. As a wave travels shoreward along the instrument transect it appears in the PT records at a progressively later time. Serial cross-correlation techniques are used to shift each record in time so that each wave in the first record aligns approximately with the corresponding wave (if it exists) in subsequent records from along the transect. A local minima analysis [Power et al., 2010] is used to delimit individual waves in each record and then parameters of interest can be determined for each wave at each PT location. The wave tracking method provides the evolution of these parameters for a single wave as it travels to shore, and they can be analysed as a function of distance or local water depth. The utility of the method is illustrated with case studies including the evolution of wave height and the evolution of the ratio of wave height to water depth for surf zone waves.
Shannon AM, Power HE, Webster JM, Vila-Concejo A, 'Correction to Evolution of coral rubble deposits on a reef platform as detected by remote sensing [Temote sensing, 5, 2013, 1-18]', Remote Sensing, 6 2743-2744 (2014) [O1]
Hughes MG, Aagaard T, Baldock TE, Power HE, 'Spectral signatures for swash on reflective, intermediate and dissipative beaches', Marine Geology, 355 88-97 (2014) [C1]
In this paper we synthesise a large data set gathered from a wide variety of field deployments and integrate it with previously published results to identify the spectral signatur... [more]
In this paper we synthesise a large data set gathered from a wide variety of field deployments and integrate it with previously published results to identify the spectral signatures of swash from contrasting beach types. The field data set includes the full range of micro-tidal beach types (reflective, intermediate and dissipative), with beach gradients ranging from approximately 1:6 to 1:60 exposed to offshore significant wave heights of 0.5-3.0. m. The ratio of swash energy in the short-wave (f > 0.05. Hz) to long-wave (f < 0.05. Hz) frequency bands is found to be significantly different between the three beach types. Swash energy at short-wave frequencies is dominant on reflective and intermediate beaches and swash at long-wave frequencies is dominant on dissipative beaches; consistent with previously reported spectral signatures for the surf zone on these beach types. The available swash spectra were classified using an automated algorithm (CLARA) into five different classes. The ordered classes represent an evolution in the spectrum shape, described by a frequency downshifting of the energy peak from the short-wave into the long-wave frequency band and an increase in the long-wave swash energy level compared to a relatively minor variation in the short-wave swash energy level. A universally common feature of spectra from all beach-states was an f-4energy roll-off in the short-wave frequency band. In contrast to the broadly uniform appearance of the short-wave frequency band, the appearance of the long wave frequency band was highly variable across the beach-states. We incorporate the results presented here and previously published observations into the morphodynamic beach-state model, and propose an ordered sequence of swash spectra under increasing and decreasing incident wave energy level. This extension of the beach-state model to include the swash zone leads to the following propositions for morphodynamic controls on the nature of the swash spectrum. (1) The short-wave part of the swash spectrum is relatively constant in form across all beach-states (f-4 energy roll-off) and the energy density per unit frequency is controlled by the beach face gradient alone. (2) The spectral bandwidth of the energy roll-off varies directly with offshore wave energy level and inversely with beach face gradient (or beach-state), in a manner consistent with the non-linear wave breaking criterion. (3) The infragravity part of the swash spectrum is highly variable in form across all beach-states and the energy level is related to the offshore wave energy level and surf zone morphology. © 2014 Elsevier B.V.
McCarroll RJ, Brander RW, Turner IL, Power HE, Mortlock TR, 'Lagrangian observations of circulation on an embayed beach with headland rip currents', Marine Geology, 355 173-188 (2014) [C1]
This study describes the first comprehensive measurements of nearshore current patterns across the entire extent of an embayed beach bounded by headland rip currents. A field expe... [more]
This study describes the first comprehensive measurements of nearshore current patterns across the entire extent of an embayed beach bounded by headland rip currents. A field experiment at Whale Beach, NSW, Australia provides valuable insights into: (i) embayment-wide spatial and temporal flow behaviour; (ii) rates of cross- and alongshore water exchange; and (iii) the influence of geological control by headlands on morphology and circulation. Lagrangian flow data was obtained using 34 GPS drifters with 293 individual deployments, over a single ebbing tidal cycle during moderate-low energy (Hs=1m) oblique wave forcing. In-situ wave and current data, and bathymetric data were also collected. Beach morphology was dominated by a large mid-beach rip channel with lesser headland rip channels. Mean flow rates were 0.6ms-1 in the mid-beach channel and 0.4ms-1 in the headland channels, with the majority of cross-shore water volume flux (~60%) through the central channel. A weak alongshore current O (0.1ms-1) was forced by the oblique offshore wave angle. Rip current velocities, flow variability, and rate of surfzone exits by Lagrangian drifters increased as water level decreased. Transient currents on a planar bar along the northern half of the beach, with mean speeds velocity standard deviation up to 0.2ms-1, were not tidally modulated. Lagrangian time series were used to differentiate four current regimes (rip cell, rip head, planar bar and offshore low energy zone) based on mean velocity, velocity variability and degree of tidal modulation. An increase in surfzone exit rates by drifters was observed from south (upwave) to north (downwave), with exit rates per drifter deployment of 22% at the south headland rip, 65% at the mid-beach open rip, and 80% at the north headland rip. The high rate of drifter exits contrasts previous observations on open coast beaches. Observed flow behaviours are attributed to wave shadowing at the upwave (protected) end of the beach, and longshore currents forced by oblique waves deflected offshore at the downwave headland. These field observations are in good agreement with recent numerical modelling. A relationship between bathymetric variability and current intensity was determined, with cross-shore average mean velocity correlating with a parameterisation of bathymetric alongshore non-uniformity. This study demonstrates that flow behaviour and exchange rates can vary along the length of an embayed beach due to geological control. This research has implications for transport of organisms, nutrients and pollutants, is relevant to beach safety practitioners, and can be used in calibration of numerical models. © 2014 Elsevier B.V.
Vila-Concejo A, Harris DL, Power HE, Shannon AM, Webster JM, 'Sediment transport and mixing depth on a coral reef sand apron', Geomorphology, 222 143-150 (2014) [C1]
This paper investigates the mechanics of sediment transport on a subtidal sand apron located on a coral reef environment. In this environment 100% of the sediment is carbonate bio... [more]
This paper investigates the mechanics of sediment transport on a subtidal sand apron located on a coral reef environment. In this environment 100% of the sediment is carbonate bioclasts generated in situ. The sand apron is located on the back reef and only affected by waves during high tides. It is commonly accepted in the literature that sand aprons are features that prograde lagoonwards and that most of the progradation occurs during high-energy events. Measurements of water depths, waves, currents and near bed suspended sediment concentrations (all at 10. Hz) on the sand apron were undertaken over a nine day intensive field campaign over both spring and neap tides; waves and tides were also measured in the lagoon. The topography and bathymetry of the sand apron were measured and mixing depth was obtained on three transects using depth of disturbance rods. We found that sediment transport on sand aprons is not solely restricted to high-energy events but occurs on a daily basis during spring tides. The main factor controlling the sediment transport was the water depth above the bed, with depths of 2-2.3. m allowing waves to promote the most sediment transport. This corresponds to a depth over the reef crest of 1.6-1.9. m. The second most important control was waves; transport was observed when Hs on the apron was 0.1. m or greater. In contrast, current magnitude was not a controlling mechanism for sediment entrainment but did affect sediment transport. The morphology of the sand apron was shown to affect the direction of currents with the currents also expected to influence the morphology of the sand apron. The currents measured during this field campaign were aligned with a shallow channel in the sand apron. Mixing depths were small (< 2.5. cm) yet they were larger than the values predicted by empirical formulae for gentle siliciclastic ocean beaches. © 2013 Elsevier B.V.
Baldock TE, Grayson R, Torr B, Power HE, 'Flow convergence at the tip and edges of a viscous swash front - Experimental and analytical modeling', Coastal Engineering, 88 123-130 (2014) [C1]
The details of flow at the tip of a viscous swash front are important to describe the propagation of the wave, the bed shear and to estimate material transport rates and impact fo... [more]
The details of flow at the tip of a viscous swash front are important to describe the propagation of the wave, the bed shear and to estimate material transport rates and impact forces. This paper presents novel experimental data illustrating the convergence of fluid at swash fronts generated by dam-break flows. Very viscous fluids (detergents) were used to slow the flow sufficiently to enable video tracking of particles on the free surface and within the interior of the flow. The experiments were performed both up a slope and on a horizontal bed. The particle tracking shows that surface particles travel faster than the mean flow, converge on the swash tip and then rapidly decelerate, a process that will induce a high bed shear stress at the swash tip as observed in recent experiments. Particles also converge on the wall boundaries because of the no-slip condition. A simple analytical model is developed to estimate the ratio of the velocity of surface particles and the wave front. For laminar flows, this ratio is found to be 3/2, independent of the bed slope and flow depth, and is in good agreement with the experimental data. The same model approach suggests a ratio of 8/7 for turbulent flows. This flow convergence does not appear to be included in either analytical modeling of the tip region or in basal resistance laws for the swash front and would modify the momentum equation at the swash tip [c.f. Hogg and Pritchard, 2004] and the kinematic boundary condition at the shoreline. The flow convergence is consistent with observations of the behavior and build-up of buoyant debris at the leading edge of tsunami wave front and can be observed in natural swash flows on beaches. © 2014 Elsevier B.V.
Vicinanza D, Baldock T, Contestabile P, Alsina J, Caceres I, Brocchini M, et al., 'Swash zone response under various wave regimes', JOURNAL OF HYDRAULIC RESEARCH, 49 55-63 (2011)
|Show 34 more journal articles|
Conference (20 outputs)
|2019||Stringari CE, Power HE, 'A Data-driven approach to the fraction of broken waves', Australasian Coasts and Ports 2019 Conference, Hobart (2019) [E1]|
|2019||Hart RM, Power HE, Hanslow DJ, 'Water level trends in NSW coastal lakes by use of exceedance probability analysis', Australasian Coasts and Ports 2019 Conference, Hobart, Tasmania (2019) [E1]|
|2019||Greenslade DJM, Uslu B, Allen SCR, Kain C, Wilson KM, Power HE, 'Evaluating tsunami warnings using inundation model results', Australasian Coasts and Ports 2019 Conference, Hobart, Tasmania (2019) [E1]|
|2019||Hanslow DJ, Fitzhenry MG, Power HE, Kinsela MA, Hughes MG, 'Rising tides: Tidal inundation in South east Australian estuaries', Australasian Coasts and Ports 2019 Conference, Hobart, Tasmania (2019) [E1]|
Wilson KM, Kendall M, Power HE, 'A comparison of tsunami inundation model results for drowned river valleys using either static or dynamic tidal inputs', Australasian Coasts and Ports 2019 Conference (2019)
© Australasian Coasts and Ports 2019 Conference. All rights reserved. Although it is common for tsunami modelling studies to apply a static tide, it is known that tsunamis and tid... [more]
© Australasian Coasts and Ports 2019 Conference. All rights reserved. Although it is common for tsunami modelling studies to apply a static tide, it is known that tsunamis and tides interact in a non-linear manner in estuaries such as drowned river valleys. Tide-tsunami interactions can both intensify and dampen the effects of tsunami depending on factors including mean basin depth. In order to demonstrate the differences between tsunami modelling with static and dynamic tides, we conducted a series of models at two New South Wales (NSW) drowned river valley locations, Sydney Harbour and Port Hacking. Boundary conditions used a wave train sourced from the T2 database to represent a tsunami sourced from a MW 9.0 earthquake at the Puysegur trench near New Zealand. The tsunami was then phased with a spring tide. Fourteen distinct dynamically tided scenarios were created by positioning the largest tsunami wave peak at hourly intervals across a complete tidal range. For every tidal stage coincident with the peak of the largest tsunami wave, the tidal level was extracted and used as a static tide level for static tide models. Direct comparisons could then be made between models with dynamic and static tides of equivalent tidal levels. Static tide models provide a simpler tsunami model setup. However results show that they may underestimate maximum inundation volumes, and become less reliable upriver, particularly beyond locations with significant water flow constrictions. Static tide models only provide results comparable to dynamic tide models for approximately 1-2 hours from tsunami arrival.
|2018||Power HE, Kinsela MA, Stringari CE, Kendall MJ, Hanslow DJ, 'Wave overwash on a rock platform: Remote sensing and pressure sensor observations', Proceedings of the Coastal Engineering Conference (2018)|
Burke A, Chang H-C, Power HE, 'MAPPING MULTIDECADAL MORPHOLOGICAL VARIABILITY VIA SATELLITE DERIVED BATHYMETRIES', IGARSS 2018 - 2018 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM, Valencia, SPAIN (2018) [E1]
|2017||Stringari CE, Harris DL, Power HE, 'Quantifying the fraction of broken waves on a high energy east coast Australian beach', Australasian Coasts & Ports 2017: Working with Nature, Cairns, QLD (2017) [E1]|
|2017||Power HE, Cossu R, Callaghan DP, Nielsen J, Hughes MG, Nielsen P, 'Lagoon stratification in Manihiki Atoll, Cook Islands', Australasian Coasts & Ports 2017: Working with Nature, Cairns, QLD (2017) [E1]|
|2017||Wilson OA, Power HE, 'Modelling the Tsunami Threat to Sydney Harbour (Port Jackson) with Comparisons to Historical Events', Australasian Coasts & Ports 2017: Working with Nature, Cairns, QLD (2017) [E1]|
Hart RM, Power HE, Hanslow DJ, 'Tidal Dynamics and Oscillations within Coastal Lakes', Australasian Coasts & Ports 2017: Working with Nature, Cairns, QLD (2017) [E1]
Wilson OA, Power HE, Hanslow D, Sexton J, Mollison K, 'Tsunami inundation in New South Wales estuaries: Developing new attenuation rules', Australian Coasts and Ports 2015 Conference (2015) [E1]
This study aims to develop new attenuation rules for tsunamis in NSW estuaries. The results of the study will be presented in full at the 2015 Coasts and Ports conference in Auckl... [more]
This study aims to develop new attenuation rules for tsunamis in NSW estuaries. The results of the study will be presented in full at the 2015 Coasts and Ports conference in Auckland, New Zealand.
Power HE, Clarke SL, Wilson O, Hubble TTCT, 'Tsunami hazard from submarine landslides: 3D inundation modelling in New South Wales, Australia', Australian Coasts and Ports 2015 Conference (2015) [E1]
This study has assessed the current state of knowledge regarding the potential for tsunami impact on the NSW coastline from submarine mass failure events. 2D modelling suggests th... [more]
This study has assessed the current state of knowledge regarding the potential for tsunami impact on the NSW coastline from submarine mass failure events. 2D modelling suggests that there is the potential for sizeable coastal flow depths, however, the lateral extent of the impact is not estimated using these methods. Preliminary 3D modelling results suggest that models are highly sensitive to model input factors resulting in significant variation in the initial sea surface waveform. This then results in varied inundation footprints. Full 3D modelling results will be presented at the conference.
Power HE, Baldock TE, 'Measurement and modelling of hydrodynamics at the surf-swash boundary', 34th IAHR Congress 2011 - Balance and Uncertainty: Water in a Changing World, Incorporating the 33rd Hydrology and Water Resources Symposium and the 10th Conference on Hydraulics in Water Engineering (2011)
© 34th IAHR Congress 2011. All rights reserved. Swash zone boundary conditions are investigated using field observations of the inner surf zone and the swash zone for a range of m... [more]
© 34th IAHR Congress 2011. All rights reserved. Swash zone boundary conditions are investigated using field observations of the inner surf zone and the swash zone for a range of micro-tidal, predominantly swell-dominated, sandy beaches. The boundary conditions are characterized in terms of a terminal bore height and the asymmetry between uprush and backwash flows. Terminal bore heights are calculated by examining wave evolution across the surf zone. This is investigated in terms of wave height to water depth ratios (?) and waves are shown to be unsaturated. These observations are used to approximate the terminal bore height at the surf swash boundary as Hb¿0.12Ho, which is consistent with recent laboratory data sets. Wave transformation modelling is used to identify conditions where the surf zone is predicted to be unsaturated and this is found to occur for steep beaches and large wave periods. A normalised beach slope parameter is derived to separate these two regions. The asymmetry between uprush and backwash flows is investigated using remote sensing techniques. The time of flow reversal in the swash zone was found to occur at approximately 40-50% of the duration of the swash cycle, which is significantly different from previous theory.
|Show 17 more conferences|
Number of supervisions
|Commenced||Level of Study||Research Title||Program||Supervisor Type|
|2020||PhD||Current and Future Evolution of Estuaries in the Age of Climate Change||PhD (Earth Sciences), Faculty of Science, The University of Newcastle||Principal Supervisor|
|2018||PhD||Tsunami Evacuation in Estuaries and Coastal Rivers: Developing New Attenuation Rules||PhD (Earth Sciences), Faculty of Science, The University of Newcastle||Principal Supervisor|
|2018||PhD||Assessing the Impact of the El Nino/Southern Oscillation on Estuary Water Levels Under Current and Future Climate||PhD (Earth Sciences), Faculty of Science, The University of Newcastle||Principal Supervisor|
|2018||PhD||Tsunami Modelling in Australian Estuarine Environments||PhD (Earth Sciences), Faculty of Science, The University of Newcastle||Principal Supervisor|
|Year||Level of Study||Research Title||Program||Supervisor Type|
|2020||PhD||Data-driven Investigations of Broken Wave Behaviour in the Surf and Swash Zones||PhD (Earth Sciences), Faculty of Science, The University of Newcastle||Principal Supervisor|
October 10, 2019
December 18, 2018
October 16, 2018
September 5, 2018
October 27, 2017
August 4, 2016
May 25, 2015
Dr Hannah Power
School of Environmental and Life Sciences
Faculty of Science
|Phone||(02) 4921 5606|
|Fax||(02) 4921 6925|
Callaghan, NSW 2308