School of Geography

Dr Alex Henshaw

Alex

Senior Lecturer in Physical Geography

Email: a.henshaw@qmul.ac.uk
Telephone: +44 (0)20 7882 5436
Room Number: Bancroft Building, Room 2.03

Profile

My research seeks to understand the processes that control the form and behaviour of rivers, from the scale of individual geomorphic units to entire drainage networks. My approach combines measurement using novel ground-based and remote sensing methods with experimentation using numerical and physical models to investigate the morphodynamic responses of river systems to changes in biota, climate and land management. I develop new techniques to help realise the geoscientific potential of emerging Earth observation data sets and process-based tools and analytical frameworks to support ecosystem service delivery in river catchments.

Key publications:

Teaching

I teach across a range of subject areas including fluvial geomorphology, geospatial science, hydrology, statistics, environmental modelling and river management. Wherever possible, I try to enhance student learning through the illustration of concepts and demonstration of techniques using active research sites and by providing opportunities to work with real research data. Examples of skills developed by students who take the modules I currently teach include flood frequency analysis and hydrodynamic modelling, river habitat assessment and restoration design, surveying, satellite image analysis and digital cartography.

Modules taught:

  • GEG5223 Geospatial Science (convenor)
  • GEG6314/GEG7314 Flood Risk Management & Modelling (convenor)
  • GEG7317 River Assessment & Restoration (convenor)
  • GEG7319 Environmental Data Acquisition & Analysis (lecturer)
  • GEG7320 Modelling Environmental Systems (convenor)

Research

Research Interests:

Morphodynamics of large rivers using emerging Earth observation data sets
The last decade has seen an explosion in the quality and availability of Earth observation data, providing opportunities to study river processes at spatial and temporal scales that would previously have proved impossible. However, making sense of river morphodynamics in this era of big data presents many research challenges. Highlights in this strand of my research include critical assessment of the potential of archival Landsat data to quantify ecomorphodynamic behaviour in large rivers (Henshaw et al., 2013a); development of automated methods to quantify sedimentary bar and channel morphodynamics in meandering and anabranching rivers (Monegaglia et al., 2018); adaptation of graph theoretical metrics more commonly used in mathematics and neuroscience for structural and behavioural analysis of braided rivers (Connor-Streich et al., 2018); and physically-meaningful remote river reach classification using process-based geomorphic indicators (Henshaw et al., 2019).

Biotic agents of change in fluvial systems
Certain species of plants and animals have the capacity to modify river form and behaviour. These so-called “ecosystem engineers” influence hydrological, hydraulic and sediment transport processes through activities such as root and stem growth, seasonal dieback, burrowing, grazing, etc. These interactions between the biotic and abiotic components of fluvial systems can have important river management implications but also, if harnessed correctly, provide a means to restore natural functioning and resilience in degraded catchments. My research in this area has identified physical controls on the growth of engineering riparian tree species (Henshaw et al., 2013); established the role of invasive burrowing animals as drivers of elevated suspended sediment yields and bank erosion in rivers (Harvey et al., 2014, 2019; Faller et al., 2015); demonstrated how large wood can modify suspended sediment transport in lowland rivers (Parker et al., 2017); and supported the parameterisation of vegetation-hydrogeomorphic process interactions in numerical modelling (Politti et al., 2018).

Supporting process-based river management and restoration
Healthy river ecosystems and the services they provide (e.g. flood protection, erosion control, nutrient cycling) are a product of natural hydrological, sedimentological and ecological processes that operate over a wide range of spatio-temporal scales. The protection, reinstatement and emulation of such processes wherever possible is key to successful river management and restoration but practitioners require knowledge and effective tools to help them identify, understand and resolve problems. My research has supported this through the development of a multi-scale hierarchical assessment framework to underpin river management decisions across Europe (Gurnell et al., 2016); stochastic forecasting of changes in upland catchment sediment yields under future land use and climate change scenarios (Henshaw et al., 2013b); and the development of GIS-based decision-support tools to assist ecosystem service provision through strategic land use management (Jackson et al., 2013)

 

 

Publications

  • Henshaw, AJ, Sekarsari, P, Zolezzi, G, Gurnell, AM. 2019. Google Earth as a data source for investigating river forms and processes: Discriminating river types using form‐based process indicators. Earth Surface Processes and Landforms. https://doi.org/10.1002/esp.4732
  • Harvey, GL, Henshaw, AJ, Brasington, J & England, J. 2019. Burrowing invasive species: An unquantified erosion risk at the aquatic‐terrestrial interface. Reviews of Geophysics. https://doi.org/10.1029/2018RG000635
  • Connor‐Streich, G, Henshaw, AJ, Brasington, J, Bertoldi, W, Harvey, GL. 2018. Let's get connected: A new graph theory‐based approach and toolbox for understanding braided river morphodynamics. WIREs Water. https://doi.org/10.1002/wat2.1296
  • Monegaglia, F, Zolezzi, G, Güneralp, I, Henshaw, AJ, Tubino, M. 2018. Automated extraction of meandering river morphodynamics from multitemporal remotely sensed data. Environmental Modelling and Software. https://doi.org/10.1016/j.envsoft.2018.03.028
  • Harvey, GL, Henshaw, AJ., Parker, C, Sayer, CD. 2018. Re-introduction of structurally complex wood jams promotes channel and habitat recovery from overwidening: Implications for river conservation. Aquatic Conservation: Marine and Freshwater Ecosystems. https://doi.org/10.1002/aqc.2824
  • Politti, E, Bertoldi, W, Gurnell, AM, Henshaw, AJ. 2018. Feedbacks between the riparian Salicaceae and hydrogeomorphic processes: A quantitative review. Earth Science Reviews. https://doi:10.1016/j.earscirev.2017.07.018
  • Trinci, G, Harvey, GL, Henshaw, AJ, Bertoldi, W, Hölker, F. 2017. Life in turbulent flows: interactions between hydrodynamics and aquatic organisms in rivers. WIREs Water. https://doi:10.1002/wat2.1213
  • Parker, C, Henshaw, AJ, Harvey, GL, Sayer, CD. 2017. Reintroduced large wood modifies fine sediment transport and storage in a lowland river channel. Earth Surface Processes and Landforms. https://doi:10.1002/esp.4123
  • He, F, Zarfl, C, Bermerich, V, Henshaw, AJ, Darwall, W, Tockner, K, Jähnig, SC. 2017. Disappearing giants: a review of threats to freshwater megafauna. WIREs Water. https://doi:10.1002/wat2.1208
  • Faller, M, Harvey, GL, Henshaw, AJ, Bertoldi, W, Bruno, MC, England, J. 2016. River bank burrowing by invasive crayfish: Spatial distribution, biophysical controls and biogeomorphic significance. Science of the Total Environment. https://doi.org/10.1016/j.scitotenv.2016.06.194
  • Politti, E, Bertoldi, W, Henshaw, AJ. 2016. Extending a hydromorphodynamic reduced complexity model with riparian vegetation dynamics, in Webb, JA, Costelloe, JF, Casas-Mulet, R, Lyon, JP, Stewardson, MJ (eds.). Proceedings of the 11th International Symposium on Ecohydraulics. Melbourne, Australia, 7-12 February 2016. The University of Melbourne, ISBN: 9780734053398.
  • Politti, E, Bertoldi, W, Henshaw, AJ. 2016. Developing allometric relationships for riparian vegetation friction characterization, in Webb, JA, Costelloe, JF, Casas-Mulet, R, Lyon, JP, Stewardson, MJ (eds.). Proceedings of the 11th International Symposium on Ecohydraulics. Melbourne, Australia, 7-12 February 2016. The University of Melbourne, ISBN: 978-0-7340-5339-8.
  • Gurnell, AM, Rinaldi, M, Belletti, B, Bizzi, S, Blameur, B, Braca, G, Buijse, T, Bussenttini, M, Camenen, B, Comiti, F, Demarchi, L, Garcia de Jalon, D, Gonzalez, del Tanago, M, Grabowski, R, Gunn, I, Habersack, H, Hendriks, D, Henshaw, AJ, Klosch, M, Lastoria, B, Latapie, A, Marcinkowski, P, Martinez-Fernandez, V, Mosselmann, E, Mountford, JO, Nardi, L, Okruszko, T, O’Hare, MT, Palma, M, Percopo, C, Surian, N, van de Bund, W, Weissteiner, C, Ziliani, L. 2016. A multi-scale hierarchical framework for developing understanding of river behaviour to support river management. Aquatic Sciences. https://doi.org/10.1007/s00027-015-0424-5
  • Garcia Lugo, AG, Bertoldi, W, Henshaw, AJ, Gurnell, AM. 2015. The effect of lateral confinement on gravel bed river morphology. Water Resources Research. https://doi.org/10.1002/2015WR017081
  • Henshaw, AJ, Bertoldi, W, Harvey, GL, Gurnell, AM, Welber, M. 2014. Large wood dynamics along the Tagliamento River, Italy: insights from field and remote sensing investigations, in Lollino, G, Arattano, M, Rinaldi, M, Giustolisi, O, Marechal, JC, Grant, G (eds.). Engineering Geology for Society and Territory, Volume 3, Proceedings IAEG XII Congress, Springer International Publishing Switzerland.
  • Gurnell, AM, Gonzalez del Tanago, M, Rinaldi, M, Grabowski, R, Henshaw, AJ, O’Hare, M, Belletti, B, Bujise, AD. 2014. Development and application of a multi-scale process-based framework for the hydromorphological assessment of European rivers, in Lollino, G, Arattano, M, Rinaldi, M, Giustolisi, O, Marechal, JC, Grant, G (eds.). Engineering Geology for Society and Territory, Volume 3, Proceedings IAEG XII Congress, Springer International Publishing Switzerland.
  • Harvey, GL, Henshaw, AJ, Moorhouse, TP, Clifford, NJ, Hoolah, H, Grey, J, Macdonald, DW. 2014. Invasive crayfish as drivers of fine sediment dynamics in rivers: field and laboratory evidence. Earth Surface Processes and Landforms. https://doi.org/10.1002/esp.3486
  • Henshaw, AJ, Gurnell, AM, Bertoldi, W, Drake, NA. 2013. An assessment of the degree to which Landsat TM data can support the assessment of fluvial dynamics, as revealed by changes in vegetation extent and channel position, along a large river. Geomorphology. https://doi.org/10.1016/j.geomorph.2013.01.011
  • Henshaw, AJ, Dangerfield, S, Thorne, CR. 2013. Sediments and geomorphology, in McIntyre, N, Thorne, CR (eds.). Land use management effects on flood flows and sediments – guidance on prediction. CIRIA.
  • Jackson, B, Pagella, T, Sinclair, F, Orellana, B, Henshaw, AJ, Reynolds, B, McIntyre, N, Wheater, H, Eycott, A. 2013. Polyscape: a GIS mapping framework providing efficient and spatially explicit landscape-scale valuation of multiple ecosystem services. Landscape and Urban Planning. https://doi.org/10.1016/j.landurbplan.2012.12.014
  • Henshaw, AJ, Thorne, CR, Clifford, NJ. 2013. Identifying causes and controls of river bank erosion in a British upland catchment. Catena. https://doi.org/10.1016/j.catena.2012.07.015
  • Harvey, GL, Moorhouse, TP, Clifford, NJ, Henshaw, AJ, Johnson, MF, Macdonald, DW, Reid, I, Rice, SP. 2011. Evaluating the role of invasive aquatic species as drivers of fine sediment-related river management problems: the case of the signal crayfish (Pacifastacus leniusculus). Progress in Physical Geography. https://doi.org/10.1177%2F0309133311409092

Supervision

Please get in touch if you are interested in undertaking a PhD or MSc by Research in the following areas:

  • Development and application of network-based methods for understanding braided river morphodynamics;
  • Numerical modelling of fluvial system responses to climate and land use change;
  • Behavioural analysis of large rivers using Google Earth Engine.

PhD students (current):

  • Yasmin Walley: Source-to-sink modelling of sediment dynamics in the South Island of New Zealand. Supervisors: Alex Henshaw (QMUL), James Brasington (Waikato). Funding: QMUL Principal’s Studentship. Expected completion 2020.

PhD students (completed):

  • Gabriel Connor-Streich: Graph theoretical analysis of braided rivers. Supervisors: Alex Henshaw (QMUL), Gemma Harvey (QMUL). Funding: QMUL Strategic PhD Studentship in River Science. Awarded 2019.
  • Fengzhi He: Diversity and risk patterns of freshwater megafauna: A global perspective. Supervisors: Sonia Jähnig (IGB Berlin), Christiane Zarfl (Tübingen), Alex Henshaw (QMUL), Klement Tockner (IGB Berlin). Funding: EU Erasmus Mundus Joint Doctorate SMART programme. Awarded 2019.
  • Bishnu Raj Baral: Numerical modelling of braiding processes in gravel bed rivers. Supervisors: James Brasington (QMUL), Alex Henshaw (QMUL), Walter Bertoldi (Trento). Funding: EU Erasmus Mundus Joint Doctorate SMART programme. Awarded 2018.
  • Matej Faller: Ecosystem engineering impacts of invasive species on river banks: signal crayfish and Himalayan balsam. Supervisors: Gemma Harvey (QMUL), Alex Henshaw (QMUL), Walter Bertoldi (Trento), Cristina Bruno (Fondazione Edmund Mach). Funding: EU Erasmus Mundus Joint Doctorate SMART programme. Awarded 2018.
  • Federico Monegaglia: Meandering rivers morphodynamics: integrating nonlinear modelling and remote sensing. Supervisors: Marco Tubino (Trento), Alex Henshaw (QMUL), Guido Zolezzi (Trento). Funding: EU Erasmus Mundus Joint Doctorate SMART programme. Awarded 2017.
  • Emilio Politti: Investigating and modelling interactions among vegetation, hydrodynamics and morphology. Supervisors: Walter Bertoldi (Trento), Alex Henshaw (QMUL). Funding: EU Erasmus Mundus Joint Doctorate SMART programme. Awarded 2017.
  • Giuditta Trinci: Spatial organisation of ecologically relevant high order flow properties and implications for river habitat assessment. Supervisors: Alex Henshaw (QMUL), Gemma Harvey (QMUL), Walter Bertoldi (Trento), Franz Hölker (IGB Berlin). Funding: EU Erasmus Mundus Joint Doctorate SMART programme. Awarded 2017.
  • Prima Sekarsari: Classifying single-thread rivers: a European perspective. Supervisors: Angela Gurnell (QMUL), Guido Zolezzi (Trento), Alex Henshaw (QMUL). Funding: EU Erasmus Mundus Joint Doctorate SMART programme. Awarded 2015.
  • Grecia Alejandra Garcia Lugo: Braided rivers: an exploratory study combining flume experiments and the analysis of remotely-sensed data. Angela Gurnell (QMUL), Alex Henshaw (QMUL), Walter Bertoldi (Trento). Funding: EU Erasmus Mundus Joint Doctorate SMART programme. Awarded 2015.