Development examples stream retention Katja Huls Healthy Waters - - PowerPoint PPT Presentation

Development examples – stream retention

Katja Huls Healthy Waters April 2018

Contents

• Stream loss numbers
• Auckland Unitary Plan rule
• Special Housing Areas
• Structure planning process
• Development examples

Stream loss

Stream Loss

Permanent Stream loss was on average in Auckland was: 10.5km per annum Long Term Plan KPI: 3.5km per annum In 2016 after partial implementation of the Auckland Unitary Plan: Permanent Streams Intermittent Streams Loss 1.4km Loss 1.4km Mitigation 3.6km Mitigation 237m Total gain 2.2km Total loss

• 1.2km

Total loss: 2.8km Total mitigation: 3.8km

Auckland Unitary Plan Rule

Auckland Unitary Plan

Objective Policy

Auckland Unitary Plan

Rule

Offsetting

Links to other stormwater drivers

Flood resilience

• Stream corridors provide for the conveyance of flood flows
• Plan for 100 year event plus climate change and maximum probable

development in the catchment

• Major overland flow paths (ephemeral streams) must be retained if flows

cannot be safely conveyed in the road corridor

• Buildings cannot be located in the floodplain in greenfield development –

a piped stream will still have a floodplain and is not developable land

Flooding and piped streams

Flood mitigation via stream daylighting

Our department is currently implementing two large flood mitigation projects by:

• Restoring a stream channel – Oakley Creek
• Creating a stream channel – Takanini Cascades

The projects provide amenity, connectivity and open space for adjacent dense development.

Links to other stormwater drivers

Water quality

Stream retention and restoration provides for much better water quality outcomes in freshwater and marine environments

• NZ Coastal Policy Statement (2010)
• maintain or enhance natural biological and physical processes/water quality
• avoid / remedy cross contamination of sewage and stormwater systems
• reduce contaminant and sediment loadings in stormwater at source
• integrated management of catchments/networks
• design options that reduce flows to stormwater networks
• National Policy Statement Freshwater Management (2014/17)
• maintain or improve overall water quality, improve where degraded
• safeguard ecosystems and health of communities by managing use of land and

discharges

• seek to halt declining trends in ecosystem health (MCI) and enhance where degraded

Development examples

Special Housing Areas in Auckland

• 26 plan changes
• 154 SHAs – 63,000 dwellings
• 23,000 in the Future Urban Zone
• Three key growth areas in North, West and South Auckland

• Wainui
• Kumeu/Huapai
• Whenuapai
• Scott Point
• Redhills
• Flat Bush

• Hingaia
• Bremner Road
• Wesley
• Belmont

Wainui

Kumeu/Huapai

Kumeu/Huapai

Whenuapai

Whenuapai

Scott Point

Redhills

Crows Road

Flat Bush

Hingaia – Karaka Brookview & KARLA

Bremner Road

Wesley

Headwater streams and wetlands protected by:

• Retention and enhancement
• Requiring infiltration of stormwater to

provide baseflow via raingardens, tree pits and infiltration trenches

• Original proposal provided 6 online
• dams. These were removed to protect

stream habitat. Flood flows were allowed to pass forward instead, generating a very minor effect on downstream rural land

Belmont

Stream channel retained and enhanced Stream daylit Flood mitigation within the green corridor Stormwater and open space integrated

Structure planning process

Structure planning process

• “Hot tub” workshops with specialists from applicant and council

teams

• Apply Water Sensitive Design
• Adjust density and housing typology
• 300m2 sections typical
• Terraced housing
• Adjust road crossings to avoid multiple stream branches
• Restore and enhance streams and wetlands
• Apply ecological corridors where relevant

Development responses

• Increase density adjacent to the stream
• “Green Street” approach with stream adjacent to the road
• Commercial area facing and integrating with streams
• Pedestrian and cycling connectivity
• Integration with flood attenuation
• Stream daylighting
• Integration of stormwater treatment and hydrology mitigation

devices

• Minimum 10m width planting either side