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The Puzzle of the Gumbasa Flow Slide - An Engineering Assessment to Build Back Better

24 May 2022
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Event type:
Virtual event, Evening meeting, Regional Group, Lecture
Organised by:
South East Regional Group
Virtual Event via Microsoft Teams
Event status:

On 28 September 2018, Central Sulawesi Province, Indonesia, experienced a 7.4 magnitude earthquake, resulting in significant loss of life and damage to dwellings and infrastructure. The 55 km long Gumbasa Irrigation System was heavily broken and irrigation of 8,000 ha of land has failed since then. Through an Emergency Assistance for Rehabilitation and Reconstruction (EARR) grant, Asian Development Bank (ADB) is funding reconstruction for the irrigation canal. Embedded in the concept and design development for reconstruction of the primary canal, Mott Macdonald undertook engineering and sustainability assessments. Rare earthquake induced high velocity flow slides posed a particular challenge, with only basic types of ground investigation technology available for characterisation purposes. Detailed geological understanding of the flow slides led to the segmental risk profiling of the canal corridor and slopes for future earthquake induced failure that suitably calibrated with the actual zones of large flow slides. The differentiating factor between lower and higher risk was found to be combinations of soil layers that exacerbated earthquake induced excess pore water pressures and led to temporary but exceptionally low levels of shear strength

The presentation will highlight the adopted approach to repair and rehabilitate the main canal using the BUILD BACK BETTER approach guided by the sustainability drivers for the project. The adopted approach and lessons learned can be used in similar settings worldwide. The project has also been submitted for the Ground Engineering Sustainability Award.


Barnali Ghosh and Edward Russell (Foundations & Geotechnics, Mott MacDonald) 

Barnali is a Technical Director at Mott MacDonald (London) and a Fellow at Institute of Civil Engineer (FICE). She is a chartered civil engineer with specialization in Earthquake Geotechnical Engineering. She was recently selected among the top 50 women in engineering in UK in 2020. She is the International Winner of the 2017 Shamsher Prakash Award for Excellence in Geotechnical Earthquake Engineering Practice. During her long career, she has acted as a seismic designer and reviewer for high-profile projects around the world. She has been propagating sustainable solutions for developing countries which have wide social outcomes. She remains connected to the academic world as a Royal Academy Visiting Professor at Cambridge University where she teaches Geo Seismic Engineering.

Edward is principal engineering geologist experienced in design, supervision and interpretation of site investigations, geological mapping and detailed soil/rock logging. Geotechnical design experience in preliminary and detailed foundation design, embankments, flood embankments, load transfer platforms, slope stability assessment and soil mixing. Experienced in supervision of construction works including tunnel portal excavations and drill and blast tunnelling. Considerable overseas experience gained in Kazakhstan, Turkmenistan, Albania, Georgia, Mozambique and Ireland.


This is a free virtual meeting via Microsoft Teams, starting at 6pm.  To join the meeting click on the link in the flier