FOSAL Categorisation framework –
methodology for making category
assessment
Document Control
Document Information
Document Name:
FOSAL Categorisation framework – methodology for making category assessment
Contact Person:
Steve Fabish, Programme Manager, FOSAL
Status:
Final
Document Review
Review Timeframe:
This document wil be reviewed as required.
Reviewers :
Document History
Author
Description of Change
Date
Version
Nedine
Approval
21/08/2023
1.0
Thatcher
Swann
Joanna Noble
Amendment
04/09/2023
1.1
Page 1 of 7
Document Approval
This document was initially approved on 21 August 2023, by Nedine Thatcher Swann, Chief Executive Gisborne
District Council at a meeting of Council’s Major Projects Steering Group. The Chief Executive also granted
authority for Joanna Noble, Director of Sustainable Futures, to approve amendments to document.
Signed:
Nedine Thatcher Swann
Chief Executive Gisborne District Council
Date:19 February 2024
An amended version (v 1.1) was approved by Joanna Noble, on 4 September 2023. This version included the
following changes:
1. Added “Response phase – rapid assessment of potentially affected dwellings”
2. Added “independent” peer review under Cat 2P step 2
3. Added “if applicable” at various steps through the Cat2 process
4. Formatting changes (various).
Signed:
Joanna Noble
Director of Sustainable Futures
.
Date 16/02/2024
Page 2 of 7
FOSAL – Gisborne District Council Categorisation decision tree – version 1.1
Response phase – rapid assessment of potentially affected dwellings
Dwelling affected or risk of damage initiated by Cyclone Gabrielle?
NO
Yes
Preliminary categorisation indicates which of the following?
CAT1
Despite not being affected in this event is property
CAT3
subject to possible ‘Future Risk’?
Refer
2P
2C
Yes
NO
2A
page 3
FUTURE WORK PROGRAM
Step 1. Update Council
Information systems
Step 1: Individual Assessment to determine if a property should become CAT 2P, CAT 2C, or CAT1 applying following
criteria:
Step 1: Identify extent and location of risk; and
identify mitigation options.
Step 2. Update
2P – Property Level interventions
2C- Community Level interventions 2A – More assessment
Landowner
required (status quo)
For inundation: Subject Matter Expert (SME) assessment of
SME assessment determines:
Further information
Step 2: Scope feasibility of mitigation options. For
vulnerability to future events includes consideration:
4. There are practical
commissioned, but not yet
community mitigations consider changes to: LTP,
Step 3. Update LIM
1. If freeboard can be achieved at 500mm above Gabrielle
options for community-
available.
Infrastructure Strategy, AMPs & Financial Strategy.
notations– if
flood heights (instead of 1%AEP), and
level intervention
applicable.
2. On-site works can reduce risk of flood waters from
5. Benefits exceed costs
entering the house; or flood hazard risk to life considered
6. The interventions are
Step 3: Consider if TRMP plan change to natural
Recommendation: Add
tolerable (based on considerations of flood water velocity
feasible
hazard risk overlay is required (i.e. controls on
notation re changing
and height (indicator metrics <2m/s, <1.5m), rate of water
7. Thresholds meet 2P (e.g
subdivision, min floor heights, etc)
nature of hazard
rise, sediment and debris loads and evacuation options)
flood heights and
information
3. Property interventions are practical and feasible.
velocity)
Step 4: Engineering Standards - update if relevant
Recommendation peer reviewed by internal team
8. Property level
For land slide: SME assessment of house (and access) vulnerability to
interventions alone are
CAT1 - Minor flood damage to
risk of further land slide/movement includes consideration of –
insufficient or not
repair but no need for
Step 5 : Education - LIM notations, comms with
• Risk of future movement to life is assessed as ‘low’ (eg Risk to
feasible to manage risk
significant redesign or
landowners, website updates
life safety threshold to be assessed – AIFR < 10-4 )
9. Interventions
retrofitting
• Assessment of risk to property
contribution to reducing
• Practical and feasible remediation of land or structures is
risk to life
possible
Recommendation peer reviewed
Recommendation peer reviewed by internal team
For River Erosion:
SME assessment of house and assess vulnerability to risk of further
erosion includes consideration of–
• Risk to life assessed as low, and/or Geotechnical assessment
does not show imminent risk (EQC imminent risk criteria).
• Practical and feasible remediation of risk is possible.
• Fluvial geomorphology factors affecting future risk
Recommendation Peer reviewed by internal team
Page 3 of 7
NEXT STEPS:
CAT 2C Step 2 Community assessment
CAT2P Step 2.
CAT 2A
CAT 1
determines:
2a – Internal Meeting of SME’s to Confirm Category
Step 2. Review status every 3 weeks for
Step 2. Advise landowner and update Council
1. Risk is tolerable
potential movement to 2P, 2C, 3 or 1
Information systems
2b - Inform landowner of proposed category
Step 3 Council decision:
Step 3. Update LIM (if applicable)
2c – Feedback from landowners about land
Step 3. Regular update to Landowner
categorisation; internal review, then independent peer
Using Gabrielle as calibration event (credible
review of decision
scenario) that:
Step 4. LIM notation – advising of process
2d –
CE signs off category
3. a community intervention is feasible
under way (if applicable)
2e – inform landowner
4. Intervention can be included in
Annual Plan, or Long Term Plan or
Hazard Management Plan**
Step 3. Where CAT 2P remains:
5. A timeframe for the intervention
that includes consideration of
• Placard remains in place
likelihood and consequence of the
• Contract for funding to ensure works are
hazard.
completed.
If decision cannot be made for community
• Monitoring to ensure works are done
intervention within reasonable timeframe, then
property wil move to CAT 3 or stays in 2C.
Step 4. LIM notation/s.72 notices updated (including
funding arrangements) – if applicable- and then again
Step 4. Inform landowners
after Step 5
Step 5. Works signed off and reviewed.
Once works are
Step 5. Update LIMS/s.72 notices (if applicable)
completed categorisation status removed
Step 6. Once works are completed and risk
mitigated/reduced to tolerable level
Categorisation status removed
6a. Update LIMs and s.72 (if applicable)
6b. Update landowner
**Hazard Management Plan – A community-scale plan that coordinates RMA, Infrastructure, Financial, Reserves and LGA planning for the purpose a delivering an outcome that reduces natural hazard
risk to that community. The purpose of the document is to provide a strategic plan, as well as being a communication tool. Use to inform business case.
A Hazard Management Plan would be consulted on with the community, and decisions would be needed on extent, timing and how costs are apportioned for each HMP.
Page 4 of 7
CAT 3 Risk thresholds
Step 1: Assess risk: In determining categorisation, a technical specialist wil consider the following classification thresholds. The final risk determination may be based on a
combination of factors and specific characteristics of individual properties.
Intolerable risk criteria Description of impacts
Likelihood
References
Inundation Flood hazard
Flood height and/or velocity such that
Flooding has occurred on multiple
https://assets.publishing.service.gov.uk/
risk is
loss of life probable - danger to life
occasions over the last 30 years. Ie
media/602bbc768fa8f50383c41f80/Flood
considered an
from deep or fast flowing water;
cyclone Gabrielle was not a ‘one off’
_risks_to_people_-
intolerable risk significant damage to buildings and
event.
_Phase_2_The_flood_risks_to_people_
to life.
contents wil occur. Egress difficult or
methodology_technical_report.pdf
not possible.
For areas with riverbed aggradation
trends, flood risk and likelihood are
Indicator metrics:
expected to increase in the future as
https://onlinelibrary.wiley.com/doi/ful /10.
bed levels rise, raising future flood
1111/jfr3.12908
> 1.5m flood height
levels.
> 2m/s velocity
Flood Hazard (nsw.gov.au)
Other considerations: speed of water
rising; volume of silt and debris
entrained; geographic features that
exacerbate hazard (e.g. val ey
confinement).
Flood risk
On-site relocation of habitable buildings With climate change the property may
cannot be
not possible
face unacceptable risk of future
sufficiently
flooding.
mitigated
Mitigation interventions not possible or
wil cost more than land value
Page 5 of 7
Landslide Landslide
Loss of life probable if continue using
Not applicable – landslide has already
Landslide Planning Guidance
hazard is
property for residential use; significant
occurred to extent that land can no
(planning.org.nz)
considered an
damage to dwelling.
longer be used
intolerable
risk to life.
Quantitative risk metric (if data
available):
(annual individual fatality
New Zealand Geotechnical Society –
Damage to
risk > 1:10,000)
Slope Stability Geotechnical Practice
property is
Unit 1 – General Guidance Part 11 –
such that
Emergency Response
future
residential use
Proposed Slope Stability Guidance
is no longer
Modules - New Zealand Geotechnical
possible.
Society (nzgs.org)
Practice Note Guidelines for Landslide
Risk Management 2007 Ref: AGS
(2007c)
https://landsliderisk.org/wp-
content/uploads/2017/04/ags_2007c2.pd
f
Landslide risk
On-site relocation of habitable buildings Not applicable – landslide has already
is unable to be not possible.
occurred to extent that land can no
reasonably
longer be used
mitigated
Remediation not possible or wil cost
more than land value
Riverbank Damage to
Even without any further weather
Annual probability of erosion
Geotechnical assessment: factor in
erosion
property
events, dwelling is at risk of significant
assumed increase in lateral erosion over
imminent and
damage
the next 12 months (not due to another
will
significant weather event).
compromise
structural
Page 6 of 7
integrity of
EQC imminent threat criteria.
dwelling.
Risk is such
that future
residential use
is no longer
possible.
Unaccepta Very High
Likelihood vs consequences to
Annual probability – see draft working
Adapted from GUIDELINE FOR
ble
property results in very high impact –
table in excel:
Acceptable cost
LANDSLIDE SUSCEPTIBILITY,
financial
can factor in property intervention costs
combined with risk.xlsx
HAZARD AND RISK ZONING FOR
cost
too
LAND USE PLANNING
(economic
(landsliderisk.org
ally
unfeasible
to manage
risks)
Next steps:
2. Property assessments reviewed by internal review group (SME’s and managers)
3. Assessment communicated to landowners
4. Opportunity given to landowners to request a review of category (including provision of technical information) and if review is requested then following
review of additional information, SME’s wil make final recommendation. The recommendation is independently peer reviewed before CE sign off (as
for CAT2P process).
5. Request to landowner to indicated wil ingness to participate in voluntary buyout
6. Land purchase negotiations initiated, and completed
7. Initiate work on long term future for land purchased by council – feed into Hazard Management Plan and TRMP review processes
Page 7 of 7
Document Outline
