1.4 Inputs Needed for ERA Acute
9
• total water column concentrations of oil (droplets and dissolved oil components)
or a potential accumulated fish larvae mortality calculated over the duration of
the simulation based on the composition of the hydrocarbons at each time step
and their toxicity, if available from an external model.
Many of the input parameters to ERA Acute from oil drift modelling are averaged
over the spill simulation time steps, i.e. oil film thickness is the average oil film
thickness in a grid cell when there has been oil in the grid cell during the simulation.
For the shoreline and seafloor compartments, the accumulated oil mass at the end of
the simulation is recorded and given as output of the oil drift model, in turn used as
input to ERA Acute to quantify the impact in these compartments.
1.4.2 Valued Ecosystem Components
As mentioned, a VEC in ERA Acute is a natural resource for which the environmental
risk is assessed. VEC data are used for the more detailed levels of analysis in ERA
Acute (see description of the levels in Sect. 1.3.3) and VECs are assigned to an
environmental compartment of their primary exposure. The VEC can be a population
of seabirds, turtles or marine mammals, sensitive early life stages (ELS) of a fish
population, a shoreline type or seafloor species or habitat/community “represented”
by a key species.
1.4.2.1 Analysis Level A.1 Impact Analysis
At level A.1 impact analysis, VEC data are not needed (see Sect. 1.3.3.1).
1.4.2.2 Analysis Level A.2 Impact Analysis
If VEC data are limited to a geographic area comprising the location and extent of
a habitat of a species, a spawning area or similar, but no details are known about
the density distributions within that area, simplified VEC data can be prepared for a
compartment to allow for an ERA Acute analysis at level A.2. The data are simple
gridded polygon data where the VEC may be present (see Sect. 3.2.1), which will
be matched with the oil spill input to limit the impact assessment to specific areas.
Many globally available GIS data are readily available for this level, requiring only
gridding of the polygons.
9
• total water column concentrations of oil (droplets and dissolved oil components)
or a potential accumulated fish larvae mortality calculated over the duration of
the simulation based on the composition of the hydrocarbons at each time step
and their toxicity, if available from an external model.
Many of the input parameters to ERA Acute from oil drift modelling are averaged
over the spill simulation time steps, i.e. oil film thickness is the average oil film
thickness in a grid cell when there has been oil in the grid cell during the simulation.
For the shoreline and seafloor compartments, the accumulated oil mass at the end of
the simulation is recorded and given as output of the oil drift model, in turn used as
input to ERA Acute to quantify the impact in these compartments.
1.4.2 Valued Ecosystem Components
As mentioned, a VEC in ERA Acute is a natural resource for which the environmental
risk is assessed. VEC data are used for the more detailed levels of analysis in ERA
Acute (see description of the levels in Sect. 1.3.3) and VECs are assigned to an
environmental compartment of their primary exposure. The VEC can be a population
of seabirds, turtles or marine mammals, sensitive early life stages (ELS) of a fish
population, a shoreline type or seafloor species or habitat/community “represented”
by a key species.
1.4.2.1 Analysis Level A.1 Impact Analysis
At level A.1 impact analysis, VEC data are not needed (see Sect. 1.3.3.1).
1.4.2.2 Analysis Level A.2 Impact Analysis
If VEC data are limited to a geographic area comprising the location and extent of
a habitat of a species, a spawning area or similar, but no details are known about
the density distributions within that area, simplified VEC data can be prepared for a
compartment to allow for an ERA Acute analysis at level A.2. The data are simple
gridded polygon data where the VEC may be present (see Sect. 3.2.1), which will
be matched with the oil spill input to limit the impact assessment to specific areas.
Many globally available GIS data are readily available for this level, requiring only
gridding of the polygons.