Resilience describes the ability of complex systems to withstand disturbance or recover from disturbance while maintaining structure and function. Resilience assessment identifies potential failure pathways due to disturbances, critical variables, and their thresholds in relation to system failure. It provides the basis for identifying management interventions to reduce system vulnerability to disturbance and enhance recovery of system structure and function. Case studies successfully applying resilience assessment are provided. For impact assessment of Ord River Irrigation Scheme, resilience assessment provided the basis for a conservation strategy for flora and fauna threatened by project clearance. Resilience analysis of policies for managing public health risks for water quality identified strengths and weaknesses of these policies for sustainable management of health risks. In assessing environmental programmes for lakes in Greater Wellington, resilience assessment identified critical variables for managing lake values. In multi-objective planning for Te Waihora/Lake Ellesmere, resilience analysis identified rehabilitation priorities without adversely affecting other lake values. A resilience approach to protecting Christchurch from flooding led to a scheme to accommodate flood flows greater than design criteria.
KEY POLICY HIGHLIGHTS
An approach to resilience assessment is provided comprising adaptive cycles, failure pathways, multiple spatial scales, and management interventions.
Examples are discussed of applications of resilience assessment to project assessment, environmental policy, environmental programmes, rehabilitation priorities, and project design.
The value added by resilience assessment to impact assessment and environmental management is discussed.
This paper provides some practical examples of the use of resilience assessment in impact assessment and environmental management. As discussed by (Jones Citation2018), there are few examples of the use of resilience assessment in the impact assessment literature. In issues where there is complexity, there can be value in using systemic thinking that underpins resilience assessment rather than cause-effect thinking that underpins impact assessment.
First, the key elements underpinning resilience assessment are described. These are:
describing processes as adaptive cycles,
defining failure pathways and the associated critical variables and their thresholds for system failure,
recognising multiple spatial scales as nested adaptive systems, and
identifying management interventions to reduce system vulnerability to disturbances.
Second, the examples of resilience assessment are discussed. The following examples are provided:
the defining of biodiversity criteria for impact assessment of the Ord River Irrigation Stage 2 proposal,
the analysis of the efficacy of policies for managing water quality impacts on public health,
the development of environmental programmes to maintain the values of lakes in Greater Wellington,
the setting of priorities for taking action to most vulnerable components of a highly degraded but still ecologically and culturally significant lake, and
the design of levees to protect Christchurch from the Waimakariri River to address the consequences of impacts of levee failure.
2. Resilience assessment
The framework for resilience assessment is based on considering socio-ecological systems as nested adaptive systems. The first element is the ‘adaptive cycle’ which describes socio-ecological systems in four phases (Gunderson and Holling Citation2002). The first phase is the ‘exploitation’ phase, which is the use of resources in the system. There is a second ‘accumulation’ phase where there is a build-up of energy or material as a result of the exploitation phase. The system can be disrupted by a ‘disturbance’ phase that leads to the release of accumulated energy or material and can potentially change the structure and function of the system. Following the disturbance phase, there is a ‘reorganisation’ phase involving the restructuring of the system. System response can be the recovery of the original system, or, a shift to an alternative system. The phases are shown diagrammatically as a Lissajous figure (). This provides the basis for assessing resilience, i.e. the capacity of a system to absorb disturbance and still retain its basic function and structure (Walker and Salt Citation2006).
A second element is the identification of failure pathways that have the potential to cause system failure and shift the system to an alternative degraded state. The lack of water availability for maintaining crop growth is an example of a potential failure pathway for agricultural systems. Other failure pathways (discussed later in the examples in the paper) are public health risks from water quality contamination and overtopping of levee systems in floods. Resilience assessment focuses on the failure pathways that create the greatest vulnerability for system collapse. Critical variables and their thresholds associated with the failure pathway are identified. Critical variables are measures that characterise the processes on failure pathways, such as the reliability of supply for irrigation systems and the biovolume of toxic cyanobacteria posing health risks in recreational waterways. Thresholds are the tipping points for critical variables that can change the state or function of a socio-ecological system. An example is the level of 1.8 mm3/L of toxic cyanobacteria for public health risk. One of the key outputs of resilience assessment is to identify possible interventions to avert system failure and reduce the vulnerability of the system to disturbance. An example is the provision of water treatment to address contamination in drinking water supplies.
A third element in resilience assessment is the nesting of adaptive cycles (Gunderson and Holling Citation2002). Systems operate at different spatial and time scales with linkages between the different scales. For example, for the analysis of an irrigation scheme, it is relevant to consider the higher spatial scale of the catchment of the irrigation intake, and the lower spatial scale of the farms being irrigated within the scheme. For resilience assessment, the analysis should cover the potential for cascading effects on scales above and below the system that is the focus of assessment, such as the regional scale higher than the catchment when addressing climate change and the paddock scale within a farm for irrigated crop management.
shows the nested adaptive system diagram for water availability for the Waimakariri Irrigation Scheme as the focal system (Jenkins Citation2015a). The irrigation scheme is connected to the higher scale of the Waimakariri River catchment through a run-of-river intake structure with the critical variable for the water availability pathway of the rate of take from the river. The irrigation scheme is connected to the lower scale of the individual farm through its distribution network with the critical variable for the water availability failure pathway of the irrigation application rate.
The adaptive cycle for water availability for the irrigation scheme can be defined as follows:
Exploitation: irrigation takes subject to river flow conditions
Accumulation: water distribution from irrigation headworks or scheme storage
Disturbance: release of irrigation water to farmers
Reorganisation: further irrigation supply from river or storage (subject to availability).
With constraints on run-of-river extraction because of environmental flow requirements, there is a low reliability of supply with full reliability from river extraction for 1 year in 42. An off-river storage with capacity to supply the entire scheme for 9 days has been built to increase the reliability of the supply to 23 years in 42. The desired reliability is 80%, i.e. 4 years in 5.
At the higher spatial scale of the Waimakariri catchment level, the critical variables for water availability relate to river flow to sustain river ecology and instream uses including flushing flows for controlling periphyton growth, river-bed nesting bird breeding, salmon passage, and kayak and jet-boat passage. The key components of the Waimakariri River catchment adaptive cycle are:
Exploitation: the rainfall that falls on the catchment that generates runoff
Accumulation: the accumulation of runoff that generates river flow
Disturbance: the volume of the water that is extracted from the river for irrigation
Reorganisation: the adequacy of the remaining flow to sustain the river ecology and use downstream of the irrigation take.
Extracting too much water for irrigation can mean that there is an inadequate flow for instream uses leading to system failure.
At the lower spatial scale of the irrigated farm, the critical variable for water availability is the potential for lost production from inadequate soil moisture. This involves managing irrigation application rates to meet soil moisture requirements for crop production. The adaptive cycle at the irrigated farm level can be described as:
Exploitation: irrigation to supplement rainfall
Accumulation: soil moisture levels on irrigated farmland
Disturbance: evapotranspiration from the soil
Reorganisation: maintain soil moisture in the 50–80% range for optimum production.
Insufficient soil moisture can lead to system failure in terms of lost production.
Examples of interventions in relation to managing water availability identified from resilience assessment included:
At the scale of the irrigation scheme: diversion of water from the river at times of high flow to irrigation scheme storage;
At the catchment scale: maintaining the frequency of flushing flows to ensure periphyton management through limitations on the irrigation take from the river; and
At the farm scale: provision of on-farm storage to give greater flexibility in matching irrigation application with soil moisture deficit.
Critical variables and associated thresholds become the targets for potential management interventions – the fourth element of the framework. Management interventions in the biophysical system of water resources can occur at each of the phases of the biophysical adaptive cycle. In the exploitation phase, it is reducing pressure on the resource (reducing vulnerability): an example in relation to lake eutrophication is reducing catchment nitrogen loads on a lake. In the accumulation phase, it is addressing legacy issues of accumulated changes in the past (enhancing adaptive capacity): an example is lake bed treatment to reduce remobilisation of phosphorus. In the disturbance/release phase, it is increasing resilience of systems to accommodate disturbance (increasing resilience): an example is lake aeration to prevent stratification. Finally in the reorganization phase, it is rehabilitating adverse effects of the system (enhance transformability): an example in addressing lake eutrophication is the reestablishment of macrophytes in a lake. This can be shown diagrammatically for interactions in the different phases of the biophysical system ().
3. Resilience assessment in impact assessment of Ord River irrigation area stage 2 proposal
The original proposal for the Ord River Irrigation Scheme Stage 2 (M2 Supply Channel) was for approximately 36,000 ha of irrigated farms, a 400,000 tonne per annum sugar mill, and associated infrastructure (Kinhill Citation2000). A two-stage assessment process was undertaken. The first stage was to assess the implications for biodiversity because of the regional significance of the flora and fauna in the project area and the potential loss of up to 50,000 ha of vegetation through clearing. There was a particular concern with the biodiversity associated with the cracking soil plains, which was the predominant soil type affected by the development. Biodiversity was of regional significance, but only limited areas in the bioregion were within the conservation reserve system.
A resilience assessment was undertaken at the regional scale to develop biodiversity criteria for project assessment. The objective was to avoid biodiversity system failure of the extinction of any species of flora and fauna. The resilience assessment indicated the need to retain at least 30% of each vegetation association (WAEPA Citation2000).
A conservation strategy was developed for the bioregion and the project, including retention of representative associations and habitats, designation of buffer areas, and connections between conservation areas. The outcome was not only conservation criteria for biodiversity management in the project area but also additions to the conservation estate in the bioregion.
4. Resilience assessment of policy for managing health risks associated with water quality
Resilience assessment can also be used to analyse the efficacy of environmental policy. One example is the analysis of the frameworks for managing key pathways for waterborne diseases (Jenkins Citation2019).
One of the frameworks considered was WHO Water Safety Plans (Ministry of Health Citation2015). The relationship of the Plan provisions to resilience assessment is set out in . The key requirements for a Plan provide the basis for describing water treatment plants as a focal system consistent with the four phases of the adaptive cycle:
The flow diagram of water source, treatment and distribution is consistent with the exploitation phase.
The identification of risks and barriers to contamination is consistent with the accumulation phase.
A risk analysis including contamination, preventative measures and corrective actions is consistent with the disturbance phase.
Contingency plans for system failure are consistent with the recovery phase.
Monitoring of implementation and outcomes is consistent with assessing overall system sustainability.
There is a clear objective of achieving drinking water standards. The boundaries of the assessment consider the treatment and storage facilities as part of a nested system. The treatment plant is within a supply catchment with a connection to the treatment plant through the supply intake. There is also a downstream distribution system connected to the treatment plant.
The Water Safety Plans also identify interventions to enhance treatment capacity that reflect interventions associated with the four phases of the adaptive cycle:
The prevention of contaminants entering the source water which is consistent with reducing the pressure on the resource.
The removal of particles from the intake water which is consistent with addressing legacy issues.
Killing germs which are consistent with increasing the resilience of the system.
Prevention of contamination after treatment which is consistent with rehabilitating adverse effects.
The framework of Water Safety Plans mirrors a resilience assessment framework. This is in contrast to the WHO Alert framework for cyanobacteria in waterways (Ministry for the Environment and Ministry of Health Citation2009). While some components of the framework reflect the resilience assessment approach, the overall framework is inadequate to achieve sustainable system management.
The Alert framework defines the critical variables for planktonic cyanobacteria (based on cyanobacteria cell volume) and for benthic cyanobacteria (based on substrate coverage). There is an ‘action’ level representing system failure, e.g. more than 50% substrate coverage of potentially toxigenic cyanobacteria. The action level is designed to protect against health effects from exposure to cyanobacteria. There is also an ‘alert’ level to identify escalation in contamination, e.g. substrate coverage in the range 20–50%, requiring increasing monitoring and notification of public health authorities. There is also a ‘surveillance’ level, e.g. up to 20% substrate coverage, where ongoing monitoring is the response. However, the only action required under the WHO Alert framework is to put in place public health warnings about the presence of cyanobacteria. The site assessment does not address contaminant sources. Consideration of downstream effects is not a requirement. There is no requirement to consider interventions to facilitate system recovery. The response is only a recognition of the degraded state and warnings to avoid contaminated areas.
5. Resilience assessment for environmental programmes
The Natural Resources Plan (Greater Wellington Regional Council Citation2015) and the Regional Freshwater Plan (Greater Wellington Regional Council Citation1999 updated 2014) provide a comprehensive list of values for waterbodies in the Greater Wellington Region. A resilience assessment of five lakes was undertaken to identify environment programmes to maintain the values of these lakes (Jenkins Citation2015b). The assessment of Lake Waitawa is discussed below.
Lake Waitawa is a small (16 ha), shallow (<7 m) coastal lake. It has a catchment of 278 ha with 94% pastoral cover, and it receives treated wastewater from Forest Lakes Camp. The lake discharges into Waitohu Stream. The lake is valued for its aquatic ecology, water-based recreation, coarse fishing, and cultural values.
From the list of values, critical variables for aquatic ecology include nutrient levels, phytoplankton blooms, invasive plants, and pest fish. For recreational values, critical variables comprise bacteriological quality and cyanobacteria levels, while for cultural values, the critical variables appear to be mana whenuaFootnote1 sites of significance. For fishing, dissolved oxygen is one critical variable. Perch and tench are also valued for recreational fishing but are at odds with indigenous aquatic ecology values.
For some of these critical variables, there are thresholds defined by national guidelines, i.e. recreational values for bacteriological quality (540 cfu/100 mL, 95th percentile) and cyanobacteria levels (1.8 mm3/l for toxic cyanobacteria). There are also some qualitative thresholds that have been set for the lake, i.e. ‘low frequency of blooms’ for phytoplankton blooms, ‘30% of naturally available area with dominance of native species’ for invasive plants, and ‘indigenous fish resilient’ for pest fish. One threshold can be based on comparison with similar lakes, i.e. the national average TLI (Trophic Level Index) of 4.8 for coastal lakes. There are also physiological thresholds such as dissolved oxygen levels for fish survival. sets out the critical variables and related thresholds for Lake Waitawa.
The potential failure pathways for Lake Waitawa are from catchment runoff, wastewater disposal, and thermal stratification leading to anoxic conditions.
For catchment runoff, it is a nested adaptive cycle at the catchment and lake scales. The adaptive cycle phases are:
Exploitation (catchment): nutrient intensive farming
Accumulation (catchment): build-up of nutrients in soil and water
Release (catchment): discharge from tributaries to lake
Exploitation (lake): nutrients in soil and water enter lake
Accumulation (lake): build-up of nutrients in water column and sediments
Release (lake): lake sediments release nutrients when lake bottom becomes anoxic
Reorganisation (lake): need to reduce in-lake releases and catchment inputs
Reorganisation (catchment): need to reduce nutrient intensity of farming.
shows the adaptive cycle phases and possible management interventions for each of the phases.
At the catchment scale, interventions to address the exploitation-phase generation of nutrients are nutrient reduction from catchment land uses (either improved land management practices for existing use or change to less nutrient-intensive uses), and stock exclusion from waterways. To address the accumulation of nutrients in waterways, one intervention is the introduction of riparian planting. To address the release of the catchment to the lake, one intervention is the reintroduction of wetlands before the stream discharges into the lake. To address accumulation in the lake water column there are interventions such as flocculation and freshwater mussels, while for accumulation in the sediments there are interventions like dredging for removal or locking the sediments in place. To counter the release of nutrients from sediments under anoxic conditions an intervention is to destratify the lake.
For wastewater process and disposal into the lake, the adaptive cycle phases are as follows:
Exploitation (wastewater): the generation of greywater and wastewater from the camp
Accumulation (wastewater): the build-up of wastewater and sludge in the treatment pond
Release (wastewater): overflow from pond into lake via wetland
Exploitation (lake): discharge of wastewater into lake
Accumulation (lake): build-up of nutrients and pathogens in the lake
Release (lake): algal growth in lake
Reorganisation: lake reorganisation is dependent on reorganisation of wastewater treatment and disposal.
These adaptive cycle phases are shown in together with possible management interventions.
A number of interventions have been identified which would improve lake water quality. At the exploitation (wastewater) phase, there could be a shift from flush to composting toilets. At the accumulation (wastewater) phase, the treatment pond could be desludged and the UV treatment increased by moving the trees that shade the pond. At the release (wastewater) phase, treatment of the overflow through the wetland could be increased through formalising wetland treatment. At the exploitation (lake) phase, rather than discharging to the lake, an alternative to land-based effluent disposal could be implemented. At the reorganisation (phase), the level of wastewater treatment could be increased to improve the quality of the effluent.
For thermal stratification, the adaptive cycle has the following phases:
Exploitation: the heating of the upper lake surface in summer
Accumulation: the upper layer of the lake increases in temperature and decreases in density
Disturbance/Release: density differences between upper and lower layers cause thermal stratification; reduced mixing leads to decline in dissolved oxygen at depth and release of nutrients from sediments
Reorganisation: surface layer cools in the autumn and winter; stratification ends, and general mixing occurs.
shows the adaptive cycle phases and potential interventions in relation to thermal stratification.
Interventions at the exploitation and accumulation phases are unlikely because the phases are driven by climate. Possible interventions at the disturbance/release phase are aeration of the bottom layer of the lake to arrest the dissolved oxygen decline, and removal or covering of the sediments to counter the release of nutrients.
6. Resilience assessment for rehabilitation priorities
Te Waihora/Lake Ellesmere is a large, shallow, brackish coastal lake in the Canterbury region of New Zealand. The lake occupies approximately 200 km2 at its typical water depth of 1 m. This is about 7% of its catchment of 2560 km2 (Taylor Citation1996). Based on lake sediment evidence, the lake changed from oligotrophic to eutrophic from the time of land clearance in the catchment for agriculture 150 years ago (Kitto Citation2010). It is now hypertrophic with the Trophic Level Index (TLI) typically between 6 and 7. There are high levels of nitrogen (total nitrogen averages around 2000 mg/m3) and phosphorus (total phosphorus around 200 mg/m3). However, phytoplankton growth is light-limited, with Chlorophyll a typically 60–90 mg/m3, due to highly suspended sediment levels from wind-driven re-suspension of bed sediments and sediment inputs from stream inflows and lake shore erosion (Hayward and Ward, Citation2009). Since 2017, there has been a toxic blue-green algae (planktonic cyanobacteria) bloom in the lake with public health warnings (LAWA website Citation2021).
The lake has been subject to multiple disturbances in the past. In addition to clearance for agriculture, artificial openings of the lake have been made since the 1870s to lower the lake level to create farmland and control flooding. The lake’s macrophyte beds (Ruppia) began to decline in 1920 and there was a shift from a macrophyte lake to a phytoplankton lake after a major storm in 1968 (the Wahine storm) uprooted most of the Ruppia plants. With the lower levels of lake openings, there has been increased wind and wave resuspension of sediment, reducing water clarity. Most recently, there has been a major expansion of dairying in the catchment with increased irrigation and nitrogen load.
While highly degraded in terms of water quality, the lake is an important wetland system, particularly as a migratory bird habitat, and, was recognised in 1981 by the International Union for the Conservation of Nature (IUCN) as being of international importance. It also provides habitat for a number of game bird species and is the most important area for game bird shooting in Canterbury. The lake and its tributaries are a commercial fishery, principally eels and flounder. It is also a regional recreational fishery, mainly for brown trout but with a significant drop after the Wahine storm in 1968 and a more gradual decline since then.
For Ngāi Tahu,Footnote2 Te Waihora has outstanding significance as a tribal taonga,Footnote3 representing a major mahinga kai,Footnote4 and an important source of mana.Footnote5 The original name for the lake is Te Kete Ika o Rākahautū (the fish basket of Rākahautū) which reflects its importance as a major tribal resource (NgāiTahu Citation2020).
The lake is a Waituna-type lagoon, a form of intermittently closed and open lake and lagoon (ICOLL), created by the interaction between fluvial and coastal processes (Kirk and Lauder Citation2000). River flow delivers sediment to the coast. Longshore drift has created a barrier across the river mouth creating a lake. With relatively low river flows, under natural conditions the lake is closed to the sea with natural openings only during flood flows. Te Waihora/Lake Ellesmere is artificially open to the sea to manage lake level, originally to manage the flooding of lakeside farmland, then to include water levels for bird habitat, and more recently for timing of openings to facilitate migration of longfin eels.
A major study was undertaken in 1996 to characterise the water quality and hydrology of the lake and the catchment, to describe activities that may influence the water quality and hydrology, identify uses and values of the lake and catchment, and identify management issues and options (Taylor Citation1996). The report identified the multiple values of the lake and demonstrated a decline in lake water quality and ecology. In the impact assessment of management issues and options, the report showed the complexity of the different systems and the conflicting requirements of different values. One example is the desirable changes in lake level for habitat improvements for different bird guilds. For waterfowl, the preference is for a permanently high lake, whereas for waders there is a preference for seasonally adjusted levels. The differences highlight the problem of defining interventions that improve all components of the lake system. Despite the comprehensive multicriteria analysis, no decisions were made on interventions to address the water quality and ecological concerns. Without a clear path forward for lake management, no action was taken.
In the resilience analysis for the lake, a number of components were found to be resilient despite the degraded state of the lake (Jenkins Citation2020). These included shortfin eels, common bullies, freshwater wetland vegetation, black-billed gulls, and the trophic status of the lake. Other components were found to be vulnerable, such as longfin eels, brown trout, ruppia beds, black swans, and water clarity. Some components were variable: flounder, freshwater inflow to the lake, and salinity. There were also invasive components taking over from native species, such as willow and Canada geese.
Consideration was then given to the vulnerable components. One example is longfin eels and the role of the lake in their life cycle. Longfin eels have an unusual life cycle:
The adults leave the lake and swim 1000s of kilometres to tropical waters
The females release eggs which are fertilised by the males, and the adults then die
The larvae drift from the Pacific Ocean towards New Zealand
As glass eels they seek connection to freshwater
As juvenile elvers they migrate upstream
They mature to become adults
The adults migrate from freshwater to seawater to complete the cycle.
It was found that there were limited lake openings around May when the adults migrate and around September when the glass eels return. One way to improve longfin eel recruitment would be to match lake openings with eel migration times.
The next stage in the resilience analysis was to examine the implications of changing the lake openings on the other values of the lake. Lake openings lower lake levels. Of particular concern was the potential to affect wader habitat, especially in the summer when freshwater inflow was low and there were high levels of migratory waders. A model of lake levels was developed to assess the effects of changing the timing of the openings. This would enable testing of how the changed regimes compared to the current opening regime designed to manage flooding of farmland and water levels for waders.
The lake-level model required measurements of inflows and outflows. Inflows were from tributary streams, rainfall on the lake, seawater seepage through the Barrier, groundwater seepage from the catchment, seawater during lake openings, and seawater overtopping the Barrier. Outflows were from outflow during lake openings, evaporation from the lake surface, and lake seepage through the Barrier. A 38-year sequence was available to model lake levels for different opening options.
The model was run for (1) the current opening regime, (2) an opening regime to facilitate spring recruitment, and (3) an opening regime to facilitate both autumn migration and spring recruitment.
Under the current operating regime, there were 18 openings during the autumn migration and 13 openings during the spring recruitment. Under the spring recruitment option, the spring recruitment openings increased to 26 but the autumn migration openings declined to 16. Under the autumn migration and spring recruitment option, the autumn migrations increased to 30 and spring recruitment increased to 22 (Horrell Citation2012).
The different opening regimes were then tested for the critical summer period for impact on lake levels for wader habitat. The analysis showed that the autumn migration/spring recruitment option marginally improved lake levels for waders compared to the current opening regime. Meanwhile, the spring recruitment regime made the situation worse for lake levels for waders.
7. Resilience assessment in project design
Resilience assessment can also be incorporated in project design. The approach of flood protection management for the City of Christchurch to flood flows for the Waimakariri River (Jenkins Citation2018) is discussed below. The traditional approach to flood management has been to provide levee protection for a flood of a specified return period. In the case of Christchurch, levees had been designed for a 1-in-500 year-flood flow of 4730 m3/s.
One of the key aspects of resilience assessment is not only considering the design threshold, i.e. protection against the 1-in-500-year flood flow, but also considering the consequences of exceeding the design threshold. There had been experience in the North Island of levee bank failure leading to flooding of ‘flood-protected’ areas and the inability of these floodwaters to return to the river because of levee banks downstream of the breach. Also, climate change projections for the east coast of the South Island are indicating the occurrence of more extreme events.
To address the risk of a larger-than-design flow and containing breakouts from levee bank failure, a secondary stopbank was provided along the alignment of a natural river terrace south of the primary levee to accommodate a 1-in-10,000-year flow of 6500 m3/s. The design concept is to contain and return breakout flows. This involves providing flood storage between the primary and secondary levees and returning the overflow to the main channel downstream after the flood peak has passed.
Allowance was also made for the exceedance of the 1-in-10,000-year flood flow. This involved a flood warning system and evacuation plan from low-lying areas. The storage between the primary and secondary levees would provide for the retention of 3 days of flood flow. This would provide a reasonable time window for evacuation compared to the instantaneous flooding of low-lying areas in the traditional solution of only providing a primary levee system.
8. Discussion and conclusions
These examples provide some indication of the value added by using resilience assessment in impact assessment and environmental management. In the case of the impact assessment of the Ord River irrigation proposal, resilience assessment not only provided the criteria for limiting biodiversity impacts of the project in relation to species loss but also indicated the biodiversity management requirements at the bioregional level. This is an example of tiered assessment addressing systemic risk at a higher spatial scale with resilience assessment incorporated in a strategic assessment in advance of a project as recommended by Jones (Citation2018).
In comparing water quality policies for public health, resilience assessment provided a basis for assessing the adequacy of the policy to provide a sustainable outcome. The WHO Water Safety Plan approach mirrored resilience requirements, while the Alert framework for cyanobacteria provided only a basis for identifying water quality system failure without providing the basis for management interventions. This resilience assessment is similar to the approach of Mahmoudi et al. (Citation2018) of applying a ‘resilience filter’ as an additional stage in impact assessment.
In the assessment of environmental programmes for maintaining the values of lakes in the Greater Wellington Region, resilience assessment provided the basis for determining the critical variables and thresholds for maintaining the values associated with lake systems. It also identified the failure pathways at the three spatial scales of catchment, discharge to lake, and within the lake, as well as possible management interventions for those failure pathways. This is an example of focusing on proactive policies for change, consistent with the suggestion of Jones (Citation2018) of incorporating resilience assessment into strategic environmental assessment.
In defining rehabilitation priorities for Te Waihora/Lake Ellesmere, resilience assessment was able to provide an approach for proceeding with rehabilitation tasks for the most vulnerable environmental values without compromising other environmental values. Whereas traditional impact assessment could only identify the advantages and disadvantages of proposed mitigations and could not provide the basis for making a decision.
In the project design of the flood management levees along the Waimakariri River to protect Christchurch, resilience assessment provided the basis for project design to address the consequences of impacts when the threshold for system failure was exceeded. This is consistent with one of Ewbank’s resilience assessment criteria of ‘buffers’ to provide capacity that can absorb and reduce the negative impacts of stresses (Ewbank Citation2016).
The examples of practice in the paper are drawn from the author’'s professional experience.
1. Mana whenua refers to the Indigenous people who have a cultural authority over the land.
2. Ngāi Tahu is the Māori tribe whose rohe (tribal territory) includes the Canterbury Region.
3. Taonga means a treasure, considered to be of value including socially and culturally valuable resources.
4. Mahinga kai means maintaining healthy populations of food species and their habitats.
5. Mana means prestige and authority.
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