Chapter 3
An ERA Acute Model Overview
Abstract ERA Acute is a model for environmental risk assessment of acute
discharges. The calculations follow a common framework for all environmental
compartments, whilst maintaining the mechanistic integrity of each compartment
and/or VEC group, by using compartment-specific inputs of oil exposure and
VEC-specific geographical distribution, vulnerability and recovery-defining parameters/functions. The method allows for using three different levels of detailing in VEC
in the exposure and impact calculations. For the highest level of detail, a second step
calculates recovery times in three time-factors, as well as the ERA Acute-specific
RDF which combines the extent of impact and recovery. The continuous functions
of impact and recovery calculations are presented in this chapter, separately for all
four compartments. All data are calculated in grid cells, facilitating the use of GIS
for viewing inputs and results. The methodology adds up impacts from grid cells to
populations, and calculates result statistics from single simulations to scenarios, to
multi-scenario DSHAs and cases.
Keywords Environmental risk assessment · Oil spill risk assessment · ERA Acute
risk functions · ERA Acute impact · ERA Acute restoration · Resource Damage
Factor
3.1 Setting up the Case and Input to Exposure Calculations
Cases and DSHAs that are analyzed in ERA Acute can consist of one or several spill
scenarios, each with a different spill rate, duration, depth (location), and probability
distributions, set up in a rate-duration matrix. A DSHA can occur with a frequency,
usually determined by historic spill statistics. Each oil spill scenario is modelled
with multiple stochastic simulations, covering different simulation periods (start
dates) and therefore representing different results of possible distribution of oil. The
conceptual build-up of an analysis-case is described in Chap. 1, see also Figs. 1.5
and 1.6.
© The Author(s) 2021
C. Stephansen et al., Assessing Environmental Risk of Oil Spills with ERA Acute,
SpringerBriefs in Environmental Science,
https://doi.org/10.1007/978-3-030-70176-5_3
33
An ERA Acute Model Overview
Abstract ERA Acute is a model for environmental risk assessment of acute
discharges. The calculations follow a common framework for all environmental
compartments, whilst maintaining the mechanistic integrity of each compartment
and/or VEC group, by using compartment-specific inputs of oil exposure and
VEC-specific geographical distribution, vulnerability and recovery-defining parameters/functions. The method allows for using three different levels of detailing in VEC
in the exposure and impact calculations. For the highest level of detail, a second step
calculates recovery times in three time-factors, as well as the ERA Acute-specific
RDF which combines the extent of impact and recovery. The continuous functions
of impact and recovery calculations are presented in this chapter, separately for all
four compartments. All data are calculated in grid cells, facilitating the use of GIS
for viewing inputs and results. The methodology adds up impacts from grid cells to
populations, and calculates result statistics from single simulations to scenarios, to
multi-scenario DSHAs and cases.
Keywords Environmental risk assessment · Oil spill risk assessment · ERA Acute
risk functions · ERA Acute impact · ERA Acute restoration · Resource Damage
Factor
3.1 Setting up the Case and Input to Exposure Calculations
Cases and DSHAs that are analyzed in ERA Acute can consist of one or several spill
scenarios, each with a different spill rate, duration, depth (location), and probability
distributions, set up in a rate-duration matrix. A DSHA can occur with a frequency,
usually determined by historic spill statistics. Each oil spill scenario is modelled
with multiple stochastic simulations, covering different simulation periods (start
dates) and therefore representing different results of possible distribution of oil. The
conceptual build-up of an analysis-case is described in Chap. 1, see also Figs. 1.5
and 1.6.
© The Author(s) 2021
C. Stephansen et al., Assessing Environmental Risk of Oil Spills with ERA Acute,
SpringerBriefs in Environmental Science,
https://doi.org/10.1007/978-3-030-70176-5_3
33