You are here: Home >

Environmental Sensitivity Indices

Major Issue - the Use of Environmental Sensitivity Indices (ESI) in the National Plan Coastal Resource Atlases

The use of ESI in oil spill atlases was a recommendation of the Dames & Moore Review of the National Plan Coastal Resource Atlas program.

Coopers and Lybrand, AMSA's internal auditors, have also recommended to AMSA to re-examine the use of ESI in State/NT Coastal Resource Atlases (CRAs).

AMSA has observed the use of ESI by the US National Oceanographic and Atmospheric Administration (NOAA) for use in Oil Spill Sensitivity Mapping for the United States.

[back to top]

Definitions

To begin this discussion the definitions of a number of acronyms is required:

CRAs (Coastal Resource Atlases): the preferred terminology for the present National Plan Oil Spill Atlases.
OSRA (Oil Spill Response Atlas): the terminology for the planned - integrated State/NT CRAs.
ESI (Environmental Sensitivity Indices): a numerical assessment/representation of the "sensitivity" of a particular environment to an oil spill as designated by NOAA.
ESM (Environmental Sensitivity Maps): a map showing ESI information and other spill response information utilising the numerical assessment of sensitivity using a colour coding.
NOAA: National Oceanographic Atmospheric Administration.

[back to top]

Guidelines on Sensitivity Mapping for Oil Spill Response

AMSA, as managing agency for the National Plan, has been funding the development of Coastal Resource Atlases for Australia (CRAs) over a number of years. Most CRAs are now digitised into Geographical Information Systems (GIS) systems and have been incorporated into contingency planning. Rather than producing environmental sensitivity ratings or gradings we recommend the production of complete resource atlases.

Predetermined environmental sensitivity maps (ESMs) tend to lock operational personnel into set response priorities, i.e. Rating 10 before 9 etc. Decisions in maritime oil/chemical spill response should be made in respect to (and trade-offs between):

the environmental objectives of the response,

health and safety of personnel and the public,

equipment and resource availability,

accessibility and possible damage to sensitive sites, and

associated economic damage.

That is, decisions made in the field with all relevant input including environmental sensitivities.

For example, how do you rate the importance of penguin colonies on a rocky foreshore vs. wetlands with no bird life vs. recreational beaches during summer season? Under ESI definitions the sensitivity ratings would be low priority, high priority and low priority - respectively.

Under the National Plan we do not believe ESI in their current form, as designated by NOAA, is the most effective way to prioritise spill response planning.

For ESI to be used as a priority basis for response it is not only necessary to address the different geomorphic coastal segments but also:

interactions of oil and coastal sediments,

persistence of oil in the habitat,

recovery time,

biological considerations,

biological damage to populations (sensitivity, size, density).

The primary objective of spill response in Australia, after protection of life, is to reduce the environmental consequences of spills and subsequent clean-up efforts. This is best achieved when CRA maps are used to identify the locations of sensitive resources before a spill occurs, so that protection priorities can be established and clean-up strategies designed in advance.

The National Plan preferred term 'CRAs' is used to distinguish the atlas from ESI ratings because these CRA maps are much more than just sensitivity ratings of foreshore environments.

CRAs help to assist scientific, environmental and other responders by identifying shoreline sensitivity to oiling, important natural and human-use resources present at the spill site as well as other important biological, environmental, cultural and other important resources. CRAs are not an end in themselves, they are the starting point for spill response planning, preventative actions, combat and logistic support.

The National Plan CRA "Oil Spill Atlas" approach has been to systematically compile a multitude of data into standard GIS formats for:

shoreline sensitivity to oil spills,

biological / environmental resources present (foreshore & marine),

human-use resource and amenity considerations, and

logistical and infrastructure information to support a response.

The US NOAA ESI shoreline sensitivity system predominantly classifies individual segments of shoreline into habitats according to:

geomorphological characteristics,

sensitivity to spilled oil,

natural persistence of oil,

and ease of clean-up.

Rankings are based on an understanding of the coastal characteristics including the relationships between physical processes and substrate that produce specific shoreline types and predictable patterns in oil behaviour and sediment transport. A detailed discussion of this ranking system is given below.

We recommend ESI and ESMs only be used as a guide to spill responders and not as a predetermined response plan.

This predetermined index may lock responders (Government & private companies) into response priorities that may not be the best considering the unique situation of each spill and oil type. This "predetermined protection/response priority plan" could be used as the basis of evidence in subsequent court proceedings if "priority maps" were not followed to the letter during a spill incident. Post spill litigation could result in order to recover costs from the responder for their actions in not following the set ESI rating designated during a spill (see Recommendation).

[back to top]

US Standard Definitions for Shoreline Environmental Sensitivity Rankings

Rankings for shoreline sensitivity are integral components of many planning activities, from sensitivity mapping to shoreline countermeasures. In the US NOAA developed definitions for each shoreline ranking that can be applied across the full range of aquatic habitats, from outer coasts and estuaries, to large lakes and rivers.

A scale of 1 to 10 is used, with subcategories indicated by "A" and "B."

Each ESI ranking is defined by a set of parameters describing:

substrate permeability (grain size),

trafficability, and mobility;

slope of the intertidal zone;

relative degree of exposure of the physical setting;

ease of clean-up; and

biological utilisation.

[back to top]

Definitions of ESI Rankings and Examples

(ref. NOAA Guidelines)

ESI No	ESTUARINE	LACUSTRINE
1 A	Exposed rocky cliffs	Exposed rocky cliffs
1 B	Exposed sea walls	Exposed sea walls
2	Exposed wave-cut platforms	Shelving bedrock shores
3	Fine- to medium-grained sand beaches	Eroding scarps in unconsolidated sediments
4	Coarse-grained sand beaches	Sand beaches
5	Mixed sand and gravel beaches	Mixed sand and gravel beaches
6	Gravel beaches and riprap	Gravel beaches and riprap
7	Exposed tidal flats	Exposed flats
8 A	Sheltered rocky shores	Sheltered scarps in bedrock
8 B	Sheltered seawalls	Sheltered seawalls
9	Sheltered tidal flats	Sheltered vegetated low banks
10 A	Salt marshes	Salt marshes
10 B	Freshwater marshes	Freshwater marshes
10 C	Freshwater swamp	Freshwater swamp
10 D	Mangroves	Mangroves

1: Exposed, Impermeable, Vertical Substrates

The essential elements of the ESI3D 1 rank are:

regular exposure to high wave energy or tidal currents.

strong wave-reflection patterns,

substrate is impermeable (usually bedrock) with no potential for subsurface penetration,

slope of the intertidal zone is 30 degrees or greater, which results in a narrow intertidal zone,

by the nature of the high-energy setting, attached organisms are hardy and accustomed to high hydraulic impacts and pressures.

Shoreline types that meet these elements include:

exposed rocky cliffs.

exposed, vertical seawalls made of concrete, wood, or metal.

Where both shoreline types exist in the same region, usually the natural shoreline is designated as 1A and the man-made equivalent is designated as 1B. These shoreline types are exposed to large waves, which tend to keep oil offshore by reflecting waves.

The substrate is impermeable so oil remains on the surface where natural processes will quickly remove any oil that does strand, within a time frame of a few weeks. Also, any stranded oil tends to form a band along the high-tide line or splash zone, above the elevation of the greatest biological value.

No clean-up is generally required or recommended.

2: Exposed, Impermeable Substrates, Non-Vertical

The essential elements of the ESI3D 2 rank are:

regular exposure to high wave energy or tidal currents,

strong wave-reflection patterns on a regular basis,

slope of the intertidal zone is usually less than 30 degrees, which results in a wider intertidal zone, although it can be less than 5 degrees and the intertidal zone can be up to hundreds of metres wide,

substrate is impermeable (usually bedrock) with no potential for subsurface penetration over much of the intertidal zone, although there can be a thin, mobile veneer of sediment in patches on the platform,

accumulations of sediments at the base of the cliff are regularly mobilised by storm waves, and

by the nature of the setting, attached organisms are hardy and used to high hydraulic impacts and pressures.

Shoreline types which meet these elements include:

exposed, wave-cut platforms in bedrock,

exposed scarps in unconsolidated sediments with associated wave-cut platforms, and

shelving bedrock shores.

Within a region, only one of these shoreline types is typically present along the exposed coast. There has never been a need for subdivision of the ESI3D 2 ranking.

As with ESI3D 1, these shorelines are low in rank because they are exposed to high wave energy. However, they have a flatter intertidal zone, sometimes with small accumulations of sediment at the high-tide line, where oil could persist for several weeks or months. When the sediments have been formed into a beach that has multiple, wave-built berms, it is designated as a separate shoreline type on the maps. Along bedrock-dominated shores, it is very common to have wave-cut platforms in combination with mixed sand and gravel or gravel beaches.

Biological impacts can be immediate and severe, particularly if fresh oil slicks cover tidal pool communities on the rocky platforms. However, the oil is usually removed quickly from the platform by wave action. Clean-up is not necessary except for removal of oiled debris and oil deposits at the high-tide line in areas of high recreational use, or to protect a nearshore resource, such as marine birds.

3: Semi-Permeable Substrate, Low Potential for Oil Penetration and Burial, Infauna present but not usually abundant

The essential elements of the ESI3D 3 rank are:

the substrate is semi-permeable (fine- to medium-grained sand), with oil penetration usually less than 10 cm,

sediments are well-sorted and compacted (hard),

the slope is very low, less than 5 degrees,

the rate of sediment mobility is low, so the potential for rapid burial is low,

surface sediments are subject to regular reworking by waves, and

there are relatively low densities of infauna.

Shoreline types that meet these elements include:

fine- to medium-grained sand beaches, and

eroding scarps in unconsolidated sediments.

Compact, fine-grained sand beaches inhibit oil penetration, and they generally accrete slowly between storms, making the potential for oil burial low. However, burial depths may be large when the oil is stranded at the beginning of a seasonal accretionary period. Clean-up is simplified by the hard substrate which can support vehicular and foot traffic. Biological use by infauna is highly variable spatially and temporally.

Eroding scarps in unconsolidated sediments are mapped as this shoreline rank, because they have a small accumulation of sediments at the base of the scarp that behaves similar to a sand beach.

4: Medium Permeability, Moderate Potential for Oil Penetration and Burial, Infauna present but not usually abundant

The essential elements of the ESI3D 4 rank are:

the substrate is permeable (coarse-grained sand), with oil penetration up to 25 cm possible,

the slope is intermediate, between 5 and 15 degrees,

rate of sediment mobility is relatively high, with accumulation of up to 20 cm of sediments within a single tidal cycle possible; there is a potential for rapid burial and erosion of oil,

sediments are soft, with low trafficability, and

there are relatively low densities of infauna.

Shoreline types that meet these elements include:

coarse-grained sand beaches.

Coarse-grained sand beaches are ranked separately and higher than fine- to medium grained sand beaches because of the potential for higher oil penetration and burial, which can be as great as one metre deep. These beaches can undergo very rapid erosional and depositional cycles, with the potential for rapid burial of oil, even after one tidal cycle. Clean-up is more difficult, as equipment tends to grind oil into the substrate because of the loose packing of the sediment. Also, clean-up techniques have to deal with multiple layers of oiled and clean sediments, increasing the amount of sediments to be handled and disposed of. These more mobile sediments usually have low infaunal populations, which are also highly variable over time and space. In some areas, there is no clear distinction between beach types because they cannot be differentiated by grain size. Under these conditions all sand beaches are ranked as ESI3D 4.

5: Medium-to-High Permeability, High Potential for Oil Penetration and Burial, Infauna present but not usually abundant

The essential elements of the ESI3D 5 rank are:

medium-to-high permeability of the substrate (mixed sand and gravel) allows oil penetration up to 50 cm,

spatial variations in the distribution of grain sizes are significant, with finer-grained sediments (sand to pebbles) at the high-tide line and coarser sediments (cobbles to boulders) in the storm berm and at the toe of the beach,

the gravel component should comprise at least 20 percent of the sediments,

the slope is intermediate, between 8 and 15 degrees,

sediment mobility is very high only during storms; thus, there is a potential for rapid burial and erosion of oil during storms,

sediments are soft, with low trafficability, and

infauna and epifauna populations are very low, except at the lowest intertidal levels.

Shoreline types that meet these elements include:

mixed sand and gravel beaches.

The gravel-sized component can be composed of bedrock, shell fragments, or coral rubble. Because of higher permeabilities, oil tends to penetrate deeply into sand and gravel beaches, making clean-up by removal of contaminated sediment difficult without causing erosion and sediment disposal problems. These beaches may undergo seasonal variations in wave energy and sediment reworking, so natural removal of deeply penetrated oil may only occur during storms with a frequency as low as 1-2 per year. Biological use is low, because of high sediment mobility and rapid drying during low tide.

These types of beaches have a wide range in relative degree of exposure, and sediment mobility can be inferred by the extent of attached fauna and macroalgae. Indicator species or assemblage coverages can be used to reflect the potential rate of sediment reworking. The presence of more than 20 percent attached algae, mussels, and barnacles indicates beaches that are relatively sheltered, with the more stable substrate supporting a richer biota. Where there are significant differences in the degree of exposure of sand and gravel beaches, the more exposed or mobile beaches are designated as 5A and the less exposed or stable beaches are designated as 5B. Pocket beaches, in particular, can have microenvironments that are more protected from wave energy (called wave shadows) where natural removal may be much slower than the adjacent beach.

6: High Permeability, High Potential for Oil Penetration and Burial

The essential elements of the ESI3D 6 rank are:

the substrate is highly permeable (gravel-sized sediments), with penetration up to 100 cm likely,

the slope is intermediate-to-steep, between 10 and 20 degrees,

rapid burial and erosion of shallow oil can occur during storms,

there is high annual variability in degree of exposure, and thus in the frequency of mobilisation by waves,

penetration can extend to depths below those of annual reworking,

sediments have lowest trafficability of all beaches,

natural replenishment rate of sediments is the slowest of all beaches, and

infauna and epifauna populations are very low, except at the lowest intertidal levels.

Shoreline types that meet these elements include:

gravel or shell beaches (subdivided by gravel classes as needed),

riprap.

Gravel beaches are ranked the highest of all beaches primarily because of the potential for very deep oil penetration and slow natural removal rates of subsurface oil. The slow replenishment rate of gravel makes removing oiled sediment highly undesirable, and so clean-up of heavily oiled gravel beaches is particularly difficult. For many gravel beaches, significant wave action (meaning waves large enough to rework the sediments to the depth of oil penetration) occurs only every few years, leading to long-term persistence of subsurface oil. Where there is a wide variation in the size of the gravel or the relative rate of sediment mobilisation by storm waves, this class can be subdivided when there are distinct grain-size classes, such as A) pebbles to cobbles, and B) cobbles to boulders as follows. Shell fragments can be the equivalent of gravel.

Fine-grained gravel beaches are composed primarily of pebbles and cobbles (from 4 to 256 cm), with boulders as a minor fraction. No sand is evident on the surface, and there is less than 20 percent sand in the subsurface. There can be zones of pure pebbles or cobbles, with the pebbles forming berms at the high-tide line and the cobbles and boulders dominating the lower beach-face.

Sediment mobility limits the amount of attached algae, barnacles, and mussels to low levels. The distinction can also be made on the basis of grain size and the extent of rounding of the sediments on a shoreline. The gravel is rounded or well-rounded only on those beaches regularly mobilised during storms.

Large-grained gravel beaches have boulders dominating the lower intertidal zone. The amount of attached algae and epifauna is much higher, reflecting the stability of the large sediments. A boulder-and-cobble armouring of the surface of the middle- to lower-intertidal zone is a common phenomenon on these beaches. Armour may have a very important effect on oil persistence in gravel beaches. Oil located beneath an armoured surface would tend to remain for a longer period of time than subsurface oil on an unarmoured beach with similar grain size and wave conditions because of the higher velocities required to mobilise the armour (Research Planning, Inc. 1991). Sub-rounded to sub-angular gravel is a very good indicator of these less mobile beaches.

Riprap is a man-made equivalent of this ESI rank, with added problems because it is usually placed at the high-tide line where the highest oil concentrations are found and the riprap boulders are sized so that they are not reworked by storm waves. Often, the only way to effectively clean riprap is by removal and replacement. Riprap can be the only shoreline type in a region with an ESI3D 6. Where gravel beaches are also present, riprap is designated as 6B.

7: Exposed, Flat, Permeable Substrate, Infauna usually abundant

The essential elements of the ESI3D 7 rank are:

they are flat (less than 3 degrees) accumulations of sediment,

the highly permeable substrate is dominated by sand, although silt and gravel components may be present,

sediments are water-saturated so oil penetration is very limited,

exposure to wave or tidal-current energy is evidenced by ripples in sand, scour marks around gravel, or presence of sand ridges or bars,

width can vary from a few metres to nearly one kilometre,

sediments are soft, with low trafficability, and

infaunal densities are usually very high.

Shoreline types that meet these elements include:

exposed tidal flats.

Exposed tidal flats commonly occur in association with other shoreline types, usually marsh vegetation, on the landward edge of the flat. Oil does not readily adhere to or penetrate the compact, water-saturated sediments of exposed sand flats. Instead, the oil is pushed across the surface and accumulates at the high-tide line. Even when large slicks spread over the tidal flat at low tide, the tidal currents pick up the oil and move it along shore. Because of the high biological use, however, impact on benthic invertebrates by exposure to the water-accommodated fraction or by smothering can be significant. Clean-up is always difficult because of the potential for mixing the oil deeper into the sediment, even with foot traffic.

8: Sheltered, Impermeable Substrate, Hard, Epibiota usually abundant

The essential elements of the ESI3D 8 rank are:

shelter from wave energy or strong tidal currents,

substrate is composed of bedrock or rocky rubble,

the type of bedrock can be highly variable, from smooth vertical bedrock, to rubble slopes, which vary in permeability to oil,

slope is generally steep (greater than 15 degrees), resulting in a narrow intertidal zone, and

there is usually a very high coverage of attached algae and organisms.

Shoreline types that meet these elements include:

sheltered vertical rocky shores,

sheltered rubble slopes,

sheltered scarps in bedrock and unconsolidated sediments, and

sheltered solid manmade structures, such as bulkheads.

Spilled oil tends to coat rough rock surfaces in sheltered settings, and oil persistence is long-term because of the low-energy setting. Mapping should differentiate between solid rock surfaces, which are impermeable to oil, and rocky rubble slopes, which tend to trap oil beneath a veneer of coarse boulders. Both types can have large amounts of attached organisms, supporting a rich and diverse community.

Sheltered, impermeable, rocky shores have the following characteristics:

bedrock shore of variable slope (from vertical cliffs to wide, rocky ledges) that is sheltered from exposure to most wave and tidal energy, and

the wider shores may have some surface sediments, but the bedrock is the dominant substrate type; thus it is termed "impermeable."

This shoreline type is usually classified as 8A.

Sheltered, semi-permeable, rocky shores have the following characteristics:

relatively steep and short rocky shore that is covered with a thin-to-thick veneer of angular rubble without any evidence of rounding or sorting by sediment transport, and

the surface rubble is highly variable in packing, but there is always some permeability in the surface material.

Other shoreline types frequently occur in combination with permeable rocky shores, which are usually classified as 8B.

Clean-up of these shorelines is always labor-intensive and can affect biological communities.

9: Sheltered, Flat, Semi-Permeable Substrate, Soft, Infauna usually abundant

The essential elements of the ESI3D 9 rank are:

they are sheltered from exposure to wave energy or strong tidal currents,

the substrate is flat (less than 3 degrees) and dominated by mud,

the sediments are water-saturated, so permeability is very low, except where burrowed,

width can vary from a few metres to nearly one kilometre,

sediments are soft, with low trafficability, and

infaunal densities are usually very high.

Shoreline types that meet these elements include:

sheltered tidal flats,

sheltered sand/mud flats, and

sheltered vegetated low banks.

The high biological use, soft substrate, and low-energy setting makes these habitats highly sensitive to oilspill impacts and almost impossible to clean. Usually, any clean-up efforts result in mixing oil deeper into the sediments and prolonging recovery. Natural removal rates are very slow. For example, in areas without a significant tidal range, sheltered flats are created by less-frequent variations in water level. These flats are unique in that low-water conditions can persist for weeks to months, providing a mechanism for contamination of sediments in areas that can be subsequently flooded.

10: Vegetated Emergent Wetlands, Saltwater/Freshwater Marshes, Mangroves

The essential element of the ESI3D 10 rank is:

various types of emergent vegetation, including herbaceous grasses and woody vegetation, cover the substrate.

marshes, mangroves, and other vegetated wetlands being the most sensitive habitats because of their:
- high biological use and value,
- difficulty of clean-up,
- limited natural flushing, and
- potential for long-term impacts to many organisms.

Where there are multiple wetland types present, different subclasses can be assigned based on:

likelihood of being oiled,

relative wave energy,

species composition, and

geomorphology.

Historically, the following subclasses have been delineated:

A. Saltwater marshes

B. Freshwater marshes (herbaceous vegetation)

C. Freshwater swamps (woody vegetation)

D. Mangroves

In previous atlases, efforts have been made to differentiate between sheltered and exposed wetlands, inferred from a rough analysis of the fetch and evidence of tidal current scour. However, there are no systematic field indicators of exposure that can be readily observed. An energy differentiation of vegetated wetland types would best be conducted using automated searches of the digital data, using fetch distances and other parameters, as discussed below.

With GIS capabilities, it may be possible to build the shoreline sensitivity classification from other basic parameters, such as substrate, sediment size or type, elevation, width, slope, effective fetch, general geomorphology, general biological sensitivity etc., and then use algorithms to calculate exposure to wave and tidal energy for each shoreline segment and assign it a sensitivity rank. However, this type of sensitivity ranking must be done in a highly supervised classification mode. Although existing intertidal habitat maps are a good source for mapping discrete sediment classes, such as gravel, sand, or mud, they are not good sources when these classes are mixed (sand and gravel), and they do not contain the information needed to identify coastal geomorphological types. The ESI assignments can be developed from field observations, aerial photography, and videography by experienced coastal geologists.

[back to top]

Sensitive Biological Resources

(ref. NOAA Guidelines)

There are numerous animal and plant species that are potentially at risk from oil spills.

Many species are wide-ranging; they can be present over large areas at any time. Maps indicating the entire area of occurrence of fish species, for example, can cover very large areas and thus do not help responders in setting protection priorities.

Natural resources are most at risk from oil spills when:

large numbers of individuals are concentrated in a relatively small area, such as bays where rafts of waterfowl concentrate during migration and over- wintering,

early life stages are present in somewhat restricted areas, such as spawning beds for anadromous fish and bird rookeries,

areas important to specific life stages or migration patterns, such as foraging or over-wintering sites, are impacted by oil,

specific areas are known to be vital sources for propagation,

the species are threatened or endangered, or

a significant percentage of the population is likely to be exposed to oil.

Associated data for each element, included at the species level, are:

life stage present, for each month of the year,

concentration present,

status, whether endangered or threatened, on State or Federal lists,

start/end dates for specific breeding activities, and

expert contacts for the resource.

Such data allows identification of the most sensitive periods for each species and determination of protection priorities on a seasonal basis. For each species or species group, detailed information is provided on the life stage present by month of year. Threatened and endangered species are indicated in a special category to show their protection/ management status.

Cautionary note

For some endangered species, there is considerable concern about showing the location on public maps. Publication of these locations might result in more public visits and thus disturbance, vandalism or illegal capture of endangered wildlife. For these location-sensitive resources, the exact location is not shown on the maps.

[back to top]

Sensitive Human-Use Resources

(ref. NOAA Guidelines)

Human-use resources at risk from oil spills can be divided into four major categories:

high-use recreational use and shoreline access areas,

officially designated natural resource management or protected areas,

resource extraction sites, and

water/foreshore associated archaeological, historical, and cultural sites.

Water resource protection includes surface water intakes, groundwater recharge zones and well fields. Contacts for water intakes (including exact location, depth of intake, use, volume, and presence of alternative sources) are critical. Groundwater protection can be of particular concern for spills of light products in rivers where wells are located in the floodplain and are hydraulically connected to the river.

Cautionary note

Site-specific information for some highly sensitive or important archaeological resources may need to be restricted in distribution to prevent unnecessary visits by the curious, as well as destruction by vandals.

Symbols

Current ESI maps use both polygons with hatched fill patterns (to indicate the spatial distribution) and symbols to identify the resource categories and groupings.

Most biological resources are best represented by polygons, although bird nesting sites may be represented as points, and fish streams usually as lines or shading. The points, polygons, and lines representing the different animal groups are colour-coded.

Resources with wide distributions on a map are shown in a box labelled "common throughout." This approach is especially important for narrow river corridors or in complicated backwater habitats, where resources tend to be concentrated and displaying all resources present will make the map unreadable. This convention greatly improves the readability of the map, yet maintains access to the data by the map user.

Most human-use features are represented as points and identified with a symbol. The symbol for a human-use feature is offset from the feature with a leader line drawn from the symbol to the feature. The boundaries of parks, preserves, protected areas, and refuges are represented as polygons to allow spatial searches, and the site name is located under the appropriate symbol.

[back to top]

Recommendation

Recommendation from 7th SSC Workshop & endorsed by NPAC:

Environmental Sensitivity Indices (ESIs) should not be used as the sole decision making tool in the determination priorities for spill response planning.

Rationale

The reduction of complex ecological, biological and socio economic data and information into one numerical index is seen as being too simplistic to be used for priority ratings in spill response. This raw environmental, cultural and infrastructure data is available within the State/NT or regional CRAs as individual information layers, and is more useful as primary information rather than being reprocessed into a simplified index with underlying assumptions that may, or may not, hold true in each case.

ESIs are useful as a "guide only" to ESCs and should not be used as the primary environmental planning tool. The emphasis must lie with evaluating the CRA data layers, and ESCs should be provided with further training in this area of use and interpretation of computerised CRAs.

The danger of using ESI ratings within contingency plans is that it could result in a "cookbook" approach to response planning that fails to consider the unique nature of the spill event and the location, the evolving circumstances, as well as the complex and often competing priorities combat authorities are faced with.

For further information and comments please email Environment Protection Response

[back to top]

last updated: 19 October 2006