Information and what is required when applying for a Flood Assessment Certificate for Commercial and Industrial buildings in an Urban zone

Information that is required to be submitted with an application for a Flood Assessment Certificate for Commercial and Industrial buildings in Urban zone

  • Application form
  • Current Record of Title for the property, issued within the last 6 months.
  • Copies of any consent notices registered on the Record of Title
  • Site plan that includes existing site ground levels in relation to a datum reference for the top of the kerb the road immediately adjacent to the site or top of kerb on the right-of-way. The plan must be certified by a Licensed Cadastral Surveyor to a datum mark which is permanent for use during the build. The datum reference shall be in New Zealand Vertical Datum NZVD2016 format. This must also show the proposed building footprint and surrounding hardstand areas.

Introduction

A more comprehensive approach is required when applying for a Flood Assessment Certificate (FAC) for commercial or industrial buildings, compared to residential properties.

The assessment must consider several factors, including surface water design, stormwater discharge, and the impact of hardstand areas on overland water flows.

This document outlines the process and considerations required to comply with Selwyn’s district plan when applying for an FAC complying with Selwyn’s district plan for a commercial or industrial use building.

Key stakeholders involved

  • Applicant: The building owner or developer applying for the FAC.
  • Licensed building practitioner (LBP)/architect: Engaged to design the building and ensure compliance with relevant standards and codes.
  • Civil engineer (if applicable): Typically engaged to design the surface water system for the site. This includes drainage systems, stormwater management, and addressing the impacts of hardstand areas on overland flow paths.
  • Selwyn District Council (SDC): The territorial authority responsible for reviewing and issuing the FAC.
  • Regional Council: Responsible for considering the discharge of surface water or stormwater into the ground or nearby water bodies. The regional council will review how stormwater is managed and the impacts on the environment.

Floor level requirements

To comply with Selwyn’s district plan, all commercial building floor levels must be at least 300mm above the 1:200-year ARI (annual recurrence interval) flood event level.

The intention of this requirement is to protect buildings and occupants from significant flood effects during extreme weather events.

Application process for Flood Assessment Certificates (FAC)

Preparation of application

The applicant must submit a surveyed site plan showing:

  • the proposed building footprint,
  • surrounding hardstand areas, and
  • existing ground levels.

A justification of the proposed finished floor level is required. This must explain:

  • how the proposed level meets the district plan's requirement of 300mm above the 1:200-year ARI event, and
  • address potential impacts on overland flow paths.

Engagement with civil engineer (if applicable)

The civil engineer will be responsible for reviewing and designing the surface water drainage system for the commercial building site. This includes:

  • Stormwater management for large hardstand areas (e.g. car parks and accessways).
  • Ensuring that surface water flows are properly managed without adversely affecting neighbouring properties or contributing to localised flooding.
  • Providing recommendations for water-sensitivity measures where appropriate.

Consultation with the regional council

Approval from the regional council is required if stormwater is being discharged to the ground or water bodies.

This can be either by:

  • compliance with the permitted activities rules of the Land and Water Regional Plan, or
  • compliance with an existing discharge consent, or
  • application for a new discharge consent.

The regional council will assess the environmental impact and ensure compliance with the relevant rules on stormwater discharge.

Your FAC design, and the subsequent building consent application, will be assessed against the information you provide about this regional council approval.

Submission of application

The applicant must submit the full application package, including:

  • the surveyed site plan,
  • civil engineer’s report (where applicable), and
  • justification for the proposed floor level.

Justifying the proposed floor level

The applicant's justification must consider several key factors:

  • Flood risk assessment

Reference the 1:200-year ARI event and explain how the proposed floor level ensures compliance with the minimum 300mm freeboard requirement.

  • Surface water design

Address how the proposed design manages surface water runoff and overland flows, particularly given the presence of significant hardstand areas.

  • Overland flow impact

Detail how the development mitigates impacts on overland flow paths, ensuring that the proposed building does not increase flood risk to surrounding areas.

  • Water sensitivity measures

Include any measures designed to reduce stormwater runoff, such as rain gardens, permeable surfaces, and detention basins.

Assessment by Selwyn District Council

Council review

Selwyn District Council will review the application to ensure the proposed building's floor level and stormwater drainage design:

  • meet district plan requirements, and
  • adequately address flood risks.

Decision and conditions

If approved, the FAC will include any conditions necessary to mitigate flood risks. These may involve:

  • specific construction methods,
  • additional water-sensitive design elements, or
  • restrictions on further development in high-risk areas.