Who we are

Our team have successfully worked together to deliver high value models and assessments while building trusting, collaborative relationships with our clients. Submergent is entirely comprised of technical staff who are engineers that have significant experience in river and urban stormwater hydrological and hydraulic modelling and have a proven track record of delivering results.

Carl and Rathika have worked closely together on wide ranging hydraulic modelling projects since 2005, including scoping and schematisation, model development, technical investigations, advice, strategies and guideline development. Together with Catherine and Ninger, who have worked alongside Carl and Rathika on multiple complex modelling projects over the last two years, our team offer capability, adaptability, a collaborative way of working, and commitment to projects.

Carl Johnson

Carl completed a Bachelors Degree in Engineering (Engineering Science) and has since worked as a modelling professional for more than eighteen years in New Zealand, Denmark, Australia, and Singapore. He has worked with wastewater models, but predominately focuses on hydrologic and 1D, 2D, and 3D hydraulic models that range in extent from large flood plains (1D/2D coupled models) to individual structures (Computational Fluid Dynamics). Carl works to develop innovative technical solutions that are both fit for purpose but are also practical to implement. He is keenly aware of and engages with the many aspects of modern flood models including: the diverse hydrology of New Zealand; effects of climate change; coastal boundaries; riverine, open channel and pipe network hydraulics; groundwater effects; representation of urban development; data and model management practices; model life cycles; and most importantly the people who build, use, and maintain these models.

Rathika Jebamony

Rathika has over twenty-two years of stormwater and wastewater modelling, project management and leadership experience, undertaking and managing a wide range of modelling projects in New Zealand, Australia and Canada. After completing her Bachelors Degree in Engineering (Engineering Science), she has worked with local authorities and engineering consultancies to deliver wastewater and stormwater management solutions. Rathika offers a broad knowledge base in system performance assessments, options analysis and flood risk. She is experienced in working alongside local authorities providing technical support, developing hydraulic modelling strategies and methodologies, as well as supporting the development of Long-Term Plans, Infrastructure Strategies, Catchment Management Plans, and has a refined understanding of issues facing a range of local authorities, consultants and private developers.

Catherine Liu

Catherine started her career in the water industry as a hydrological engineer in 2000 when she graduated from her Bachelors degree in Water Resources and Hydrology Engineering. She has undertaken many projects and research tasks since then, including catchment flood forecasting, flood control strategy development, water resource management and dam safety analysis. Over the last few years she has focused on flood risk assessments, stormwater management, stormwater device design and overland flow path design. In this work she regularly uses her considerable understanding of hydrological and hydraulic principles, along with her advanced skills in GIS spatial analysis tools, and modelling packages (DHI MIKE, HEC-RAS, HEC-HMS and TUFLOW HPC with quadtree and sub grid sampling) to ensure high-quality deliverables.

Ninger Kong

After completing her degree in Civil Engineering and then a PhD in "Embankment breach erosion induced by overtopping", Ninger has spent the last three years building and using hydraulic models and using them for flood risk assessments, optioneering, wastewater model calibration, long term system performance for level of service investigations, and planning assessments. She has used her depth of hydraulic knowledge to understand and enhance her models and has used her programming skills to develop many tools to streamline modelling processes and analysis. Ninger has strong skills using TUFLOW, MIKE and HEC-RAS modelling packages along with proficiency in QGIS and Python programming.

Claire Barker