Costs and Benefits of Ecosystem-based Adaptation for Flood Risk Reduction in Fiji

Transcription

1 Costs and Benefits of Ecosystem-based Adaptation for Flood Risk Reduction in Fiji Adam Daigneault & Pike Brown Landcare Research NZ 58 th AARES Conference 5 February 2014

2 Introduction Ba catchment, Fiji impacted by several natural disasters in 2012 Jan: 1-in-50 yr flood; March: 1-in-25 yr flood Some mitigation and adaptation has been done, but impacts are still large Several hard and ecosystem-based adaptation approaches are possible

3 Ecosystem-based Adaptation Which ecosystem-based alternatives to hard infrastructure cost-effectively mitigate disaster risk, particularly flooding?

4 Ecosystem-based Approaches CBD: Adaptation that integrates the use of biodiversity and ecosystem services into an overall strategy to help people adapt to the adverse impacts of climate change. TEEB: For every $1 of cost incurred in restoring/maintaining 9 biomes, benefits range from $3 to $75 dollars. Naumann et al. (2011): The majority of projects using ecosystembased approaches can be considered as beneficial from an economic point of view [however] ecosystem-based approaches are likely to be more cost-effective than traditional engineered approaches Rao et al. (2012): Suggest that EbA strategies are often orders of magnitude cheaper than engineering options

5 Methodology Cost-benefit analysis approach used to systematically assess adaptation options Primary data collected to quantify baseline impacts of flood events Hydrological model created to estimate impacts of adaptation measures Secondary data, GIS, and literature used to support additional assumptions

6 STUDY SITE BA CATCHMENT, FIJI

7 Study Site: Ba Catchment Fiji Islands

8 Flood Height (m) Flood Risk in Ba Catchment 2009 Jan 2012 Mar Ba River Flood Height at Rarawei Mill (m) R² = Year of Flood Event

9 Study Site: Ba Catchment

10 Surveys - Household 295 households surveyed electronically 168 hh 14 villages (100% itaukei) 127 hh in 14 settlements (89.8% Indo-fijian) Questionnaire Demographics, education, health Cropping, livestock, fishing, forestry Labour income, remittances, durable goods, housing Community resilience Climate, weather, and disasters 2,700+ data points per household Length :approx. 90 mins

11 Current Adaptation Approaches Adaptation Option % Villages Reinforce buildings 44% Request government assistance 33% Designate evacuation centre 19% Change cropping practices/varieties 17% Dredge river 14% Raise buildings 11% Relocate buildings 8% Store crops/food supply 8% Save money for disaster response 8% Plant mangroves 3% Plant trees 3% Construct diversion channel 3% Plant riparian buffers along waterways 0% Protect reef 0% Create fire break, fire bans 0% Change forestry practice/harvest ages 0% Plant native vegetation in floodplains 0% Improve village drainage system 0% Construct sea wall 0% Reinforce stream and river banks 0% Develop evacuation plan/committee 0% HARD SOFT ECOSYSTEM- BASED

12 About a 1-in-50 year event

13 January Flood Damage - % of Income <10% 10-20% 20-30% 30-40% 40-50%

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15 March Flood Damage - % of Income <10% 10-20% 20-30% 30-40%

16 Annual Income and Damage as a Share of Income Annual Income (FJD) Jan Floods March Floods itaukei-fijian $8,070 26% 9% Indo-Fijian $8,580 15% 11% Jan Flood caused the most damage on average in itaukei households generally more affected than Fijian households.

17 $14,000,000 Total Household Damages Ba Catchment $12,000,000 $10,000,000 $8,000,000 $6,000,000 $4,000,000 Indirect Durables Housing Livestock Crops $2,000,000 $- Jan Flood March Flood

18 Total Damages ($/household/event) $9,000 $8,000 $7,000 $6,000 $5,000 $4,000 $3,000 $2,000 $1,000 Flood Annual Exceedence Probability Ba Catchment Current Climate Expected Annual Damage: - itaukei: $186/hh/yr - Fijian: $185/hh/yr BaLower1 BaLower2 BaLower3 BaLower4 BaLower5 BaLower6 BaMid1 BaMid2 BaMid3 BaMid4 BaMid5 BaMid6 BaMid7 BaMid8 Balevutu Bukuya Buyabuya Koro Koroqaqa Nadrugu Nailaga Nakoroboya Nanoko Nanuku Navala Toge Tubuquto Votua $- 0% 5% 10% 15% 20% 25% Probability of Flood Event

19 COST-BENEFIT ANALYSIS

20 EbA Options Planting riparian buffers Plant native vegetation as 50m buffer along all stream-banks Afforesting upper catchment Plant trees on 27,400 ha of talisiga in upper catchment Planting Floodplain Vegetation plant native vegetation on 10% of cropland in mid and lower catchment

21 Hard Options Riverbank reinforcement Construct levies and other hard infrastructure along stream-bank of lower and midcatchment Dredging Dredge lower portion of Ba River Raising Houses Elevate living area of 3,000 most vulnerable houses in the catchment

22 Quantified Costs and Benefits Monetised Costs Labour Capital Operations & Maintenance Monitoring Opportunity Costs - Agriculture Opportunity Costs - Forestry Monetised Benefits Avoided Damages - Agriculture Avoided Damages - Livestock Avoided Damages Housing Avoided Damages Durable assets Avoided Damages Indirect costs Provision of non-timber forest products

23 Benefits not directly measured (yet) Maintenance of soil fertility Carbon sequestration Biodiversity & habitat Potential recreation values Spiritual values

24 Effectiveness Adaptation Option Range of Effectiveness Base Effectiveness Riparian buffers 10-40% 25% Upland afforestation 20-70% 50% Floodplain vegetation 10-25% 20% Riverbank reinforcement 30-80% 50% Raise houses 50-90%^ 75%^ Dredging river 30-80% 50% Future analyses will focus on sensitivity of effectiveness of options *Effectiveness measured as % reduction in annual expected damages ^Applies to damages to housing and durable assets only

25 Total Damages ($/houseohld/event) $4,000 Flood Annual Exceedence Probability Ba Catchment $3,500 $3,000 $2,500 $2,000 $1,500 Baseline Riparian buffers Upland afforestation Floodplain vegetation Riverbank reinforcement Raise houses Dredging river $1,000 $500 $- 0% 5% 10% 15% 20% Probability of Flood Event

26 CBA Specification Metric Base CBA Sensitivity Analysis Discount Rate 8% 4%, 12% Project period 100 years n/a Climate Scenario Current A1B climate change Estimate net present value (NPV) of costs and benefits

27 $60.0 NPV of Adaptation Options ($M) - Current Climate $40.0 $20.0 $0.0 -$20.0 -$40.0 -$60.0 -$80.0 -$100.0 NPV Costs -$120.0 NPV Benefits Total NPV -$140.0 Riparian buffers Upland afforestation Floodplain vegetation Riverbank reinforcement Raise houses Dredging river

28 $80.0 NPV of Adaptation Options ($M) - Current Climate (r = 4%) $60.0 $40.0 $20.0 $0.0 -$20.0 -$40.0 -$60.0 -$80.0 -$ $120.0 NPV Costs NPV Benefits Total NPV -$140.0 Riparian buffers Upland afforestation Floodplain vegetation Riverbank reinforcement Raise houses Dredging river

29 $40.0 NPV of Adaptation Options ($M) - Current Climate (r=12%) $20.0 $0.0 -$20.0 -$40.0 -$60.0 -$80.0 -$100.0 NPV Costs NPV Benefits -$120.0 Total NPV -$140.0 Riparian buffers Upland afforestation Floodplain vegetation Riverbank reinforcement Raise houses Dredging river

30 Climate Change Impacts Most studies on climate change in Pacific forecast greater frequency of extreme rainfall events. Hay (2006) estimates return periods for a daily rainfall of at least 40 cm on Viti Levu are as follows: * Frequency 190 years 185 years 46 years 25 years January 2012 Ba flood was approximately 45cm in 48 hours With climate change, this will be a 1 in 25 year event *Projection

31 Total Damages ($/household/event) $8,000 $7,000 $6,000 $5,000 Flood Annual Exceedence Probability Ba Catchment Expected Annual Damage ($/hh/yr): Current Climate Chg itaukei $185 $405 Fijian $186 $355 $4,000 $3,000 $2,000 Ba Average Household - Current Climate Ba Average Household - Climate Change $1,000 $- 0% 5% 10% 15% 20% Probability of Flood Event

32 $60.0 NPV of Adaptation Options ($M) - Climate Change $40.0 $20.0 $0.0 -$20.0 -$40.0 -$60.0 -$80.0 -$100.0 NPV Costs NPV Benefits -$120.0 Total NPV -$140.0 Riparian buffers Upland afforestation Floodplain vegetation Riverbank reinforcement Raise houses Dredging river

33 Summary Ba catchment, Fiji, faces high damages from flooding and other natural disasters Detailed socio-economic surveys and biophysical data used to quantify costs and benefits of adaptation options EbA only options that yield +ive NPV Hard options appear to have too high input cost relative to avoided damages

34 Future Research Mix of options in specific areas of the catchment Distributional impacts Transaction costs and ability to implement Benefits of risk reduction for other disasters

35 Parallel economic analysis being conducted for Penang (Rakiraki) Catchment, Ra, Fiji Alternative Study Area

36 Vinaka Vakalevu Adam Daigneault Senior Economist Landcare Research Auckland, New Zealand Pike Brown Senior Economist Landcare Research Auckland, New Zealand