MoSSaiC - reducing the risk of landslides in developing countries through the management of slope stability in communities
Submitting InstitutionUniversity of Bristol
Unit of AssessmentGeneral Engineering
Summary Impact TypeTechnological
Research Subject Area(s)
Earth Sciences: Physical Geography and Environmental Geoscience
Agricultural and Veterinary Sciences: Other Agricultural and Veterinary Sciences
Engineering: Environmental Engineering
Summary of the impact
An engineering methodology, Management of Slope Stability in
Communities (MoSSaiC), has been developed to mitigate urban
landslide risk in developing countries, and has been implemented in the
Eastern Caribbean. The World Bank is now including the methodology in
disaster risk mitigation projects more widely in the Latin America and
Caribbean regions, starting with Jamaica (September 2011-). MoSSaiC
centres on the efficient management of surface water (construction of
hillside drainage networks) and is delivered through a community-focussed
programme with a benefit-cost ratio of 2.7:1. The impact includes:
- Hillsides of unauthorised housing, previously exhibiting landslides
during rainfall events that occur once every two years, have now been
successfully stabilised and, in 2010, withstood a 1 in 500 year event.
- ~800 homes in 12 vulnerable urban communities have benefitted from
MoSSaiC interventions in three island states in the Caribbean.
- Indirect benefits such as rainwater harvesting, reduced water bills
and the saving of community relocation costs for Governments.
In 2011, the World Bank selected 13 methodologies for an `Aid
Effectiveness Showcase' exhibition at its Washington DC
headquarters. Due to its effectiveness, MoSSaiC was included as the only
methodology relating to landslides.
Surface water infiltration is recognised as the dominant mechanism in
triggering landslides in weathered slope materials in the humid tropics.
The first model, combining the effects of hydrological and geotechnical
processes on slope stability, was developed by Anderson (UoB since 1985)
at the University of Bristol . This two-dimensional finite difference
model, CHASM, was extended by Holcombe (UoB since 2002) & Anderson in
2003, from predicting landslide hazard (the likelihood and
mechanism of landslide occurrence), to the quantification of landslide risk.
This was achieved by modelling post-failure slope geometries, landslide
runout, costs of debris removal and slope re-instatement, and the
associated economic cost . This research enabled different slope
stabilisation investment scenarios to be tested for multiple slopes, over
budget cycles and design lifetimes, via an integrated cost-benefit
Development of a risk reduction methodology
In 2004, the Government of Saint Lucia requested that Holcombe and
Anderson develop a prototype methodology (incorporating CHASM), to address
landside risk in unauthorised urban communities. The underpinning research
findings were: i) previous locally-engineered approaches to slope
stabilisation in communities using retaining walls were ineffective ;
ii) local slope features and soil water convergence were critical in urban
landslide hazard assessment; iii) unsaturated and saturated soil
conditions need to be modelled. CHASM simulations confirmed the slope
destabilising trigger was rainfall and waste water infiltration,
controlled by altered natural drainage patterns and micro-topography (a
result of urbanisation); processes occurring at a resolution finer than
conventional slope stabilisation analyses had accounted for. A
systems-based methodology (MoSSaiC) was thus designed to stabilise
landslide-prone hillsides by the efficient management of surface water.
The pilot research in the Eastern Caribbean provided the context for
further development of CHASM to represent localised human and physical
aspects of urban landslide risk, including point water sources, structural
loading on slopes and landslide travel distances. A progressive landslide
in one community provided a test case for the code. CHASM analysis, driven
by observed rainfall, successfully replicated the timing, location and
travel distance of the landslide and confirmed the role of surface water
convergence in triggering and continuing to mobilise the failure. Local
shear box apparatus for measuring soil strength was benchmarked against a
state-of-the-art direct shear box at the University of Bristol, and
parameter uncertainty was accounted for in simulations [4,5].
Risk reduction implementation
This underpinning research facilitated slope stability management scenario
testing which demonstrated that reducing surface water infiltration could
stabilise many landslide-prone slopes. To achieve such reductions in
sub-surface water levels, an integrated network of surface drains was
designed and constructed to intercept rainfall runoff from slopes in 11
further at-risk communities (2006-2011). Household roof- and grey-water
was connected to the drains. The new drains intercepted 70% of surface
water runoff, reduced pore water pressures, and lowered ground water
This combination of research and on-the-ground construction produced the
MoSSaiC methodology for delivering community-based landslide risk
reduction to urban areas in developing countries (www.mossaic.org).
The methodology integrates technical and management aspects by capturing
local knowledge, expertise, and proven local drain design and construction
practices, from residents, contractors, and government engineers. This
holistic systems methodology drove policy change in which slope water
management was accepted as a means of reducing landslide risk at the
community scale. An initial endorsement of the scientific basis and
delivery of the pilot MoSSaiC intervention was the 2007 Trevithick award
from the Institution of Civil Engineers .
References to the research
 *A.J.C. Collison, M.G. Anderson and D.M. Lloyd, 1996. Impact of
vegetation on slope stability in a humid tropical environment: a
modelling approach. Proceeding of the ICE — Water Maritime and
Energy, 112, 168-175, dx.doi.org/10.1680/iwtme.1995.27662. Awarded the
Institution of Civil Engineers' Trevithick Award in 1997.
 *E.A. Holcombe, S. Smith, E. Wright and M.G. Anderson, 2012. An
integrated approach for evaluating the effectiveness of landslide hazard
reduction in vulnerable communities in the Caribbean. Natural
Hazards, 61, 351-385, dx.doi.org/10.1007/s11069-011-9920-7 (listed
 J.R. Blake, J.-P. Renaud, M.G. Anderson and S.R. Hencher, 2003. Prediction
of rainfall-induced transient water pressure head behind a retaining
wall using a high-resolution finite element model, Computers and
Geotechnics, 30 (6), 431-442, dx.doi.org/10.1016/S0266-352X(03)00055-7.
 *N.A.S. Hamm, J.W. Hall and M.G. Anderson, 2006. Variance-based
sensitivity analysis of the probability of hydrologically induced slope
instability. Computers & Geosciences, 32 (6), 803-817,
 J.-P. Renaud, M.G. Anderson, P.L. Wilkinson, D.M. Lloyd and D. Muir
Wood, 2003. The importance of visualisation of results from slope
stability analysis. Proceedings of the ICE — Geotechnical
Engineering, 156 (1), 27-33, dx.doi.org/10.1680/geng.2003.156.1.27.
 M.G. Anderson E.A. Holcombe, 2006. Sustainable landslide risk
reduction in poorer countries. Proceedings of the ICE — Engineering
Sustainability, 159, 23-30, dx.doi.org/10.1680/ensu.2006.159.1.23. Awarded
the Institution of Civil Engineers' Trevithick Award in 2007.
* References that best indicate the quality of the underpinning research.
Details of the impact
How research was exploited
The research and landslide mitigation methodology was delivered using a
systems engineering, structured development process, from concept  to
delivery of construction on the ground (Table 1). The systems engineering
approach required coordination not just within the public sector, but also
between the public sector, civil society and the private sector; it
integrated efforts not just vertically within a sector, but horizontally
across sectors and geographically within a country. Early evidence of the
uptake of the methodology is provided by the St Lucia Government Cabinet
Conclusion #618 of 12 July 2004, which formalised the role of MoSSaiC
Management Committee within Government. As a result of MoSSaiC project
impact in the Eastern Caribbean, in September 2009 The World Bank approved
funding for Anderson and Holcombe to author a book on the methodology to
make it more widely available [a].
Table 1: Steps used to implement the MoSSaiC methodology from 2008
|1 International agencies engage
with MoSSaiC in the Eastern
||2008 — MoSSaiC projects in communities visited by World
Bank, Caribbean Development Bank and USAID in St Lucia
and Dominica, and UNDP in St Vincent and Bequia.
Agencies and Governments provide ~US$6M for drain
construction for MoSSaiC projects [b].
|2 World Bank incorporates
MoSSaiC methodology in
disaster mitigation projects
||World Bank funds St Lucia Second Disaster Mitigation
project 2009-2011, incorporating MoSSaiC approach to
landslide risk reduction in a further six communities [b].
|3 World Bank incorporates
MoSSaiC as a case study in
||Inclusion of methodology in World Bank, World
Development Report 2010; ‘Climate Change and
Development’ [c] and featured in the World Bank’s Aid
Effectiveness Showcase in Washington DC, 2011 [d].
|4 World Bank publishes book on
MoSSaiC as an accepted
methodology suitable for
||Publication of book: M.G. Anderson and E.A. Holcombe,
2013. Community-based landslide risk reduction: Managing
disasters in small steps. 455pp, [a].
Details of the beneficiaries
Since 2008, the MoSSaiC methodology has benefitted 12 communities,
totalling approximately 3000 inhabitants, across St Lucia, Dominica and St
Vincent and the Grenadines. In 2011, it was introduced to Jamaica through
a programme of community-based projects costing US$2.37M, funded by the
World Bank and implemented by the Office of Disaster Preparedness and
Emergency Management [e].
Details of the nature of the impact and indicators
The methodology works: there have been no reported landslides in
any of the communities in which MoSSaiC interventions have been completed
. The Latin America and Caribbean Regional Disaster Risk co-ordinator
at the World Bank comments: "In the aftermath of Hurricane Tomas
(October 2010), there were numerous landslides in St. Lucia due to the
extreme rainfall. None were reported in any of the communities with
MoSSaiC interventions. This positive proof of the powerful results...
has motivated St. Lucia to scale-up the initiative nationwide, and to
institutionalize it" [f]. In addition, it has been noted that these
communities "used to be affected by substantially weaker events in the
The methodology pays: it has a benefit-cost ratio of 2.7:1 [2,h].
In this study, the development and application of an integrated landslide
risk assessment and cost-benefit analysis methodology was grounded in data
acquired at this community scale — overcoming some of the methodological
issues regarding scale, data availability and process representation and
allowing the degree of landslide risk (and risk reduction) to be
quantified. Conducting a survey of community benefits, using both revealed
preference and stated preference (contingent valuation) methods, allowed
estimation of indirect project benefits. These indirect benefits to the
community were shown to be significant and included: lower water bills
through the harvesting of intercepted rainwater from rooftops; improved
access to and from the community due to reduced flooding and associated
debris on footpaths; and therefore fewer days of work missed and less time
spent clearing debris. In St Lucia, these benefits were valued at
EC$12,705 annually . In addition, over 80% of programme funds were
spent in the communities [c] with, for example, 25 local people employed
on the project.
The methodology is being scaled up by The World Bank: Funding was
awarded for development of the functional and technical specification of
an online interface to MoSSaiC resources. The interface will give
structured access to the MoSSaiC book, and technical and project
management tools; allow development agencies and governments to design and
deliver landslide risk reduction projects; provide training modules for
the local teams delivering the landslide hazard reduction measures; and
include relevant calculators and tools for slope stability assessment and
drainage design. The combination of the ePractice user mode, user types,
content and functionality are particularly novel and innovative. It is
anticipated that the interface will become a template for other resources
in the field of Disaster Risk Management knowledge transfer both at The
World Bank and elsewhere. The specification was completed and signed-off
in June 2012 and will be built by and hosted with World Bank funding (for
which an agreement is in place). Creating a state-of-the-art interface for
all MoSSaiC resources, bespoke for each audience type at a site funded and
hosted by the World Bank, will enable global reach of the methodology, and
maximise impact in the period 2011-2014 beyond the current levels of
In addition, the World Bank is translating the book into Spanish (in
2013) and is establishing a `community of practitioners' in Latin America
and the Caribbean to roll out the methodology within the region. The World
Bank comments that "given this context of apparent success [in St.
Lucia], the World Bank sees the potential to encourage uptake of the
methodology more widely. To that end the Bank is publishing
in December 2012 the book `Community-based landslide risk
reduction — managing disasters in small steps'... [and] a Spanish
translation of the book will later be published by the Bank" [f].
CHASM software recognition: CHASM software is recognised
internationally as `industry standard', with the US-based Scientific
Software Group marketing the software since 2000 [i], achieving CHASM
sales in more than 17 countries worldwide. In 2010, CHASM was awarded the
Grand Prize at the Random Hacks of Kindness#1 software event at
Microsoft, Washington DC [b].
Sources to corroborate the impact
[a] `Community-based landslide risk reduction: Managing
disasters in small steps'. Malcolm Anderson and Elizabeth
Holcombe. Book published by the World Bank, 2013, 456pages. ISBN
[b] Latin America and Caribbean Regional Disaster Risk co-ordinator,
[c] World Development Report 2010: Climate change and development.
MoSSaiC included as a case study on page 327.
[d] Aid effectiveness showcase, World Bank Main Complex, Washington DC,
October 2011. http://www1.worldbank.org/operations/aideffectiveness/Showcase4.html
(see Saint Lucia:
"Community-based Landslide Risk Reduction" link to presentation slides).
[e] Jamaica: Jamaica Observer article Landslide risk reduction
project coming, 26th October 2011.
[f] Latin America and Caribbean Regional Disaster Risk co-ordinator,
World Bank — letter, October 2012.
[g] World Bank, Results in Action web article Saint Lucia: From
Landslides to Stability, 2011.
[h] Vice-President for sustainable development, World Bank, uses MoSSAiC
example in her speech at the TEDx event in Sendai, Japan 2012.
start time 7.08.
[i] Scientific Software Group CHASM sales page on www.scisoftware.com