ECOBAS: Social Cost-Benefit Analysis
Preliminary results
November 26, Stijn Reinhard
Objective
Preliminary Social CostBenefit Analysis of the ecoengineered oyster reef
structures along the coasts
of Kutubdia Island, to get
an indication of its
attractiveness and
information on data-gaps
Social Cost Benefit Analysis - introduction
• Compare four alternatives against the reference (Earthen
Embankment)
• All effects are taken into account (positive & negative)
• Effects with money transfer (e.g. investments costs) and
without money transfer (e.g. ecosystem services )
• Costs and benefits in future are valued as Net Present
Value (NPV) using a discount rate
• If benefits exceed costs measure could be attractive
Social Cost-Benefit Analysis
 Total costs (‘once only’
investment costs and
‘continuous’ operations and maintenance costs)
 Costs: predominantly in quantitative, monetary terms
 Benefits: qualitative (+/-) and monetary (value oyster
harvest in BDT)
 Net Present Value (NPV) of alternatives compared to the
qualitative benefits
Preliminary CBA in early phase
 Determine all effects
 Collect available information + estimation of data gaps
 Preliminary CBA-results
 Sensitivity analysis to test robustness
 Identification of important effects (related to largest
costs and benefits)
 Collect missing information
Five alternatives elaborated
Compare autonomous development (Earthen
Embankment=EE) with each alternative
#
Alternatives
Secondary measure
1
Earthen Embankment
-
2
EE with shoulders
-
3
4
5
EE + secondary
measure(s)
Oyster Reef Structure
Mangroves
Oyster reef and mangroves
Sensitivity analysis
To assess the robustness of
the analysis:
• Different discount rates
(5.0%, 7.5%, 10.0%)
• Time horizons (30, 50 &
100 years)
Benefits included in CBA
EE
EE + Shoulder
EE + Reef
structure (RS)
EE + Mangrove
EE + RS +
Mangrove
Oyster
Flood
Erosion DepoWave
yield
protec
sition
break
+
0
0
+
++
+
0
+
+
+
0
+
++
++
++
++
+++
+++
++
+++
+
+
Benefits not (yet) included in CBA
SLR
EE
EE Shoulder
G&S (e.g.
Crab)
0
+
0
++
TOT.
1+
2+
EE + RS
0/+
++
2.5+
EE + Mangrove
++
+++
5+
+++
++++
7+
EE + RS + Mangrove
Unit costs in BDT*1000
Options
Unit
Once Only
Continuous
Construction Instal- TOTAL Inspec Maintenance TOTAL
lation
tion
costs
Mat.
Lab.
Mat. Lab.
Earthen
Embankment
EE+Shoulder
1 km
Concrete Ring
45m
720
240
Mangroves
1 ha
175
40
1 km
34,625
9,669
44,294
0
1,731
483 2,215
149,673 17,566 12,232 179,471
120
1,497
553 2,169
1,085
125
75
32
232
215
180
100
50
330
125
Expected Lifetime earthen embankment
(100% replacement after ..years)
25
20
1-5 year
15
5-10 year
10-20 year
10
20-30 year
>30 year
5
0
EE
EE+Sh
EE+RS
EE+Mang
EE+RS+Mang
Discounted Costs and Benefits (mln. BDT
per 1 km coast) NPV- Discount rate = 7.5%
600.0
500.0
400.0
300.0
200.0
100.0
0.0
EE
EE+Sh
EE+RS
EE+Mang
EE+RS+Mang
Benefits (mln. BDT),
Disc. rate=7.5%, Time horizon 50 years
600.0
500.0
400.0
30 year
300.0
50 year
100 year
200.0
100.0
0.0
EE
EE+Sh
EE+RS
EE+Mang
EE+RS+Mang
Net Present Value (mln. BDT)
Different discount rates - 50 yr time horizon
900.0
800.0
700.0
600.0
500.0
5.0%
400.0
7.5%
10.0%
300.0
200.0
100.0
0.0
EE
EE+Sh
EE+RS
EE+Mang
EE+RS+Mang
Preliminary conclusions
(Based on the assumptions applied)
 The combination of earthen embankment + oyster reef
structure + mangrove (EE+RS+Mang) has the least
costs for flood safety
 EE+RS+Mang also produces largest benefits, which are
not yet valued in monetary units (e.g. crab, wood,
honey)
 EE+RS+Mang provides more adaptation possibilities
than the other measures analysed
 The change in lifetime of earthen embankment
determines the results
Thank you!
We welcome your
comments