Dr Steven Sandi Rojas

Dr Steven Sandi Rojas

Associate Lecturer

School of Engineering

Career Summary

Biography

Steven is originally from Costa Rica, where he graduated as a Civil Engineer in 2012. Soon after, he was recruited as a junior engineer by the "Comision Nacional de Emergencias (CNE)" due to the work of his Final Graduation Project: Hydro-graph Generation from Tomas Tropical Storm to Evaluate Urban Infrastructure in the Virilla River Basin.     

In 2013, he moved to Australia to start his doctoral studies at the University of Newcastle where he obtained a Ph.D. in Environmental Engineering in 2018. The focus of his research was the development of eco-hydrological and eco-geomorphological models of coastal and freshwater wetland vegetation and to explore vegetation dynamics under scenarios of climate change. His work integrates the use of hydrodynamic flood modelling and the study of vegetation dynamics.   

In 2019, he started a position as an Associate Lecturer where he delivers the courses CIVL2040 Engineering Probabilities and CIVL3470 Contaminant Hydrogeology as well as continuing his work on wetland dynamics modelling.


Qualifications

  • PhD (Environmental Engineering), University of Newcastle
  • Bachelor of Engineering (Civil), Universidad de Costa Rica

Keywords

  • Eco-geomorphology
  • Eco-hydrology
  • Wetland Modelling

Languages

  • Spanish (Mother)
  • English (Fluent)

Fields of Research

Code Description Percentage
060204 Freshwater Ecology 20
090702 Environmental Engineering Modelling 40
040608 Surfacewater Hydrology 40

Professional Experience

UON Appointment

Title Organisation / Department

Academic appointment

Dates Title Organisation / Department
1/4/2018 - 30/6/2019 Associate Researcher Faculty of Engineering and Built Environment - The University of Newcastle (Australia)
School of Engineering
Australia

Teaching

Code Course Role Duration
CIVL3410 Hydrobiological Modelling
Faculty of Engineering and Built Environment - The University of Newcastle (Australia)
Tutor 1/6/2014 - 31/12/2016
CIVL2040 Engineering Probabilities
Faculty of Engineering and Built Environment - The University of Newcastle (Australia)
Course coordinator and lecturer 1/1/2019 - 1/7/2020
CIVL2310 Fluid Mechanics
Faculty of Engineering and Built Environment - The University of Newcastle (Australia)
Tutor 1/1/2015 - 31/12/2017
CIVL2050 Engineering Computations and Probability
Faculty of Engineering and Built Environment - The University of Newcastle (Australia)
Tutor 1/1/2016 - 31/12/2017
CIVL4330 Hydrology
Faculty of Engineering and Built Environment - The University of Newcastle (Australia)
Tutor 1/1/2018 - 1/7/2018
SURV3650 Spatial Data Sytems and Remote Sensing
Faculty of Engineering and Built Environment - The University of Newcastle (Australia)
Lecturer 1/8/2018 - 31/12/2018
CIVL3470 Contaminant Hydrogeology
Faculty of Engineering and Built Environment - The University of Newcastle (Australia)
Course coordinator and lecturer 1/7/2019 - 31/12/2019
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Publications

For publications that are currently unpublished or in-press, details are shown in italics.


Journal article (5 outputs)

Year Citation Altmetrics Link
2020 Sandi SG, Saco PM, Rodriguez JF, Saintilan N, Wen L, Kuczera G, et al., 'Patch organization and resilience of dryland wetlands', Science of the Total Environment, 726 (2020) [C1]
DOI 10.1016/j.scitotenv.2020.138581
Co-authors Jose Rodriguez, Garry Willgoose, George Kuczera, Patricia Saco
2020 Saco PM, Rodríguez JF, Moreno-de las Heras M, Keesstra S, Azadi S, Sandi S, et al., 'Using hydrological connectivity to detect transitions and degradation thresholds: Applications to dryland systems', Catena, 186 (2020) [C1]

© 2019 In arid and semi-arid ecosystems, shortage of water can trigger changes in landscapes¿ structures and function leading to degradation and desertification. Hydrological conn... [more]

© 2019 In arid and semi-arid ecosystems, shortage of water can trigger changes in landscapes¿ structures and function leading to degradation and desertification. Hydrological connectivity is a useful framework for understanding water redistribution and scaling issues associated with runoff and sediment production, since human and/or natural disturbances alter surface water availability and pathways increasing/decreasing connectivity. In this paper, we illustrate the use of the connectivity framework for several examples of dryland systems that are analysed at a variety of spatial and temporal scales. In doing so, we draw particular attention to the analysis of coevolution of system structures and function, and how they may drive threshold behaviour leading to desertification and degradation. We first analyse the case of semi-arid rangelands, where feedbacks between the decline in vegetation density and landscape erosion reinforces degradation processes driven by changes in connectivity until a threshold is crossed above which the return to a functional system is unlikely. We then focus on semi-arid wetlands, where decreases in water volumes promote terrestrial vegetation encroachment that changes drainage conditions and connectivity, potentially reinforcing redistribution of flow paths to other wetland areas. The analysis of dryland wetlands is based on a novel hydrologic connectivity index derived using inundation requirements for wetland vegetation associations. The examples presented highlight the need to incorporate a coevolutionary framework for the analysis of changing connectivity patterns and the emergence of thresholds in arid and semi-arid systems.

DOI 10.1016/j.catena.2019.104354
Citations Scopus - 3Web of Science - 2
Co-authors Jose Rodriguez, Patricia Saco
2019 Sandi SG, Saco PM, Saintilan N, Wen L, Riccardi G, Kuczera G, et al., 'Detecting inundation thresholds for dryland wetland vulnerability', Advances in Water Resources, 128 168-182 (2019) [C1]
DOI 10.1016/j.advwatres.2019.04.016
Citations Scopus - 2Web of Science - 2
Co-authors Patricia Saco, Jose Rodriguez, Garry Willgoose, George Kuczera
2018 Sandi SG, Rodríguez JF, Saintilan N, Riccardi G, Saco PM, 'Rising tides, rising gates: The complex ecogeomorphic response of coastal wetlands to sea-level rise and human interventions', Advances in Water Resources, 114 135-148 (2018) [C1]
DOI 10.1016/j.advwatres.2018.02.006
Citations Scopus - 12Web of Science - 9
Co-authors Jose Rodriguez, Patricia Saco
2017 Rodriguez JF, Saco PM, Sandi S, Saintilan N, Riccardi G, 'Potential increase in coastal wetland vulnerability to sea-level rise suggested by considering hydrodynamic attenuation effects', Nature Communications, 8 1-12 (2017) [C1]
DOI 10.1038/ncomms16094
Citations Scopus - 33Web of Science - 27
Co-authors Patricia Saco, Jose Rodriguez
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Conference (9 outputs)

Year Citation Altmetrics Link
2018 Sandi SG, Saco PM, Kuczera G, Wen L, Saintilan N, Rodriguez JF, 'Predicting floodplain inundation and vegetation dynamics in arid wetlands', E3S Web of Conferences, Lyon-Villeurbanne, France (2018) [E1]
DOI 10.1051/e3sconf/20184002019
Co-authors Jose Rodriguez, George Kuczera, Patricia Saco
2016 Sandi Rojas S, Rodriguez JF, Saco PM, Riccardi G, Wen L, Saintilan N, 'Hydrodynamics, vegetation transition and geomorphology coevolution in a semi-arid floodplain wetland.', Geophysical Research Abstracts, Vienna (2016)
Co-authors Jose Rodriguez, Patricia Saco
2016 Sandi SG, Rodriguez JF, Saco PM, Wen L, Saintilan N, 'Simulation of the vegetation state and flow regime interaction in the Macquarie Marshes', Proceedings of the International Conference on Fluvial Hydraulics RIVERFLOW 2016, Saint Louis, USA (2016) [E1]
Citations Scopus - 1
Co-authors Patricia Saco, Jose Rodriguez
2016 Sandi SG, Rodriguez JF, Saco P, Wen L, Saintilan N, 'Linking hydraulic regime characteristics to vegetation status in the Macquarie Marshes', Proceedings of the 11th International Symposium on Ecohydraulics, Melbourne, Australia (2016) [E1]
Co-authors Jose Rodriguez, Patricia Saco
2015 Seoane M, Rodriguez JF, Sandi Rojas S, Saco PM, Riccardi G, Saintilan N, Wen L, 'Coevolution of hydrodynamics, vegetation and channel evolution in wetlands of a semi-arid floodplain', Geophysical Research Abstracts, Vienna (2015)
Co-authors Jose Rodriguez, Patricia Saco
2015 Rodriguez JF, Sandi Rojas S, Riccardi G, Stenta H, Saco PM, 'Estuarine wetland evolution including sea-level rise and infrastructure effects.', Geophysical Research Abstracts, Vienna (2015)
Co-authors Patricia Saco, Jose Rodriguez
2015 Sandi S, Rodriguez J, Saco P, Saintilan N, Wen L, Kuczera G, 'Development of a vegetation dynamics model for freshwater wetland assessment in the Macquarie Marshes', The Art and Science of Water - 36th Hydrology and Water Resources Symposium, HWRS 2015 (2015)

© 2015, Engineers Australia. All rights reserved. The configuration of the Macquarie Marshes is a mosaic-like collection of swamps, marshes and lagoons. The Macquarie Marshes is a... [more]

© 2015, Engineers Australia. All rights reserved. The configuration of the Macquarie Marshes is a mosaic-like collection of swamps, marshes and lagoons. The Macquarie Marshes is also one of the most ecologically important wetland systems in Australia. It contains unique plant communities that serve as a sanctuary for many species of waterbirds and other fauna such as frogs and mammals. A significant deterioration of the ecological features of the Macquarie Marshes has been recorded in the past decades. This fact is mostly attributed to reductions of the input discharges to the marshes due to water allocations for industrial, agricultural and domestic usage. Reduction of water supply translates into changes of the hydraulic regime which has a direct impact on the flood dependent vegetation species of the marshes. The complexity of the system and its ecological significance requires the use of an adequate computational tool that would allow for a realistic assessment of the site. In this paper we present initial work regarding the development of a vegetation dynamics model that can integrate vegetation establishment with time aggregated characteristics of the flow. We simulate floods on a fictional wetland by implementing a quasi-2D hydrodynamic model (VHHMM 1.0) over a rectangular cell grid. This same grid constitutes the basis for a cellular vegetation model that can calculate changes in the vegetation for each element inside the domain. The work presented here for a fictional site was developed in order to test the capability of our model to recreate consistent vegetation gradients by using deterministic transitional rules. These rules relate time aggregated characteristics of the flow such as flood period and depth of water to water requirements of different vegetation communities. We found that a well calibrated set of deterministic transitional rules based on water preferences can recreate consistent vegetation distributions; however, succession and critical conditions for succession rules will have to be defined for a specific site application. Further development of this model will result in a strategic tool for managing environmental water allocations and water sharing plans in the Macquarie Marshes.

Citations Scopus - 2
Co-authors George Kuczera, Patricia Saco, Jose Rodriguez
2015 Rodriguez JF, Seoane M, Saco, Sandi Rojas, 'A geomorphological modelling approach for landscape evolution analysis of the Macquarie Marshes, Australia', e-proceedings 36th IAHR World Congress, The Hague, The Netherlands (2015)
Co-authors Jose Rodriguez, Patricia Saco
2014 Sandi Rojas SG, Rodríguez JF, Saco P, Riccardi G, Wen L, Saintilan N, et al., 'Macquarie river floodplain flow modeling: Implications for ecogeomorphology', River Flow 2014 (2014) [E1]

This work presents preliminary results of implementing a quasi-2D hydrodynamic module (VMMHH 1.0) to simulate flows and flooding patterns throughout the Macquarie Marshes, south e... [more]

This work presents preliminary results of implementing a quasi-2D hydrodynamic module (VMMHH 1.0) to simulate flows and flooding patterns throughout the Macquarie Marshes, south east Australia, in order to assess habitat requirements. The model uses an interconnected cell scheme that solves mass conservation and uses simplified versions of the momentum equations to represent flow between cells. This model has been used before to assess geomorphological changes in large river floodplains and vegetation evolution in estuarine wetlands, showing results consistent with cases of gradual floodplain inundation following overbank flow. The simplified characteristics of the quasi-2D model allow for an adequate representation of hydrodynamic processes with similar performance of other higher dimensional models. Model results and computational times are compared with outputs from a conventional 1D/2D model (MIKE FLOOD) applied to the same domain showing that the VMMHH 1.0 is adequate for representation of floods in the Macquarie Marshes.

Citations Scopus - 2Web of Science - 1
Co-authors Patricia Saco, Jose Rodriguez
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Research Supervision

Number of supervisions

Completed0
Current1

Current Supervision

Commenced Level of Study Research Title Program Supervisor Type
2020 PhD Improving Water Management and Security by Applying Remote Sensing Tools PhD (Environmental Eng), Faculty of Engineering and Built Environment, The University of Newcastle Co-Supervisor
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Dr Steven Sandi Rojas

Position

Associate Lecturer
Department of Civil and Environmental Engineering
School of Engineering
Faculty of Engineering and Built Environment

Contact Details

Email steven.sandirojas@newcastle.edu.au
Phone (02) 49216703

Office

Room EA121
Building EA Building
Location Callaghan
University Drive
Callaghan, NSW 2308
Australia
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