Morphum Environmental Ltd Environmental Engineers and Consultants www'morphum'com

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Morphum Environmental LtdEnvironmental Engineers
and Consultantswww.morphum.com
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• LIDAR Survey, Modelling and GIS as tools used in
  the Sustainable Management of Urban Drainage
  Systems

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Damian Young Morphum Environmental Ltd John
Tate North Shore City Council
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The Assessment of Overland Flow Paths in North
Shore City
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Todays Presentation

• Outline method to identify, validate and protect
  Overland Flow Paths (OLFPs)in the urban
  environment of North Shore City.
• How we assess the impacts to and from OLFPS
• LIDAR Survey, Modelling and GIS support
  sustainability objectives

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What is an Overland Flow Path?

• Overland flow path
• The route followed by stormwater which runs over
  the surface of the ground (overland flow) when it
  becomes concentrated as it makes its way downhill
  following the path of least resistance towards
  streams and watercourses or the sea.

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What is LIDAR ?

• In 2004 a LIDAR (Light Detection and Ranging)
  survey was flown of NSC.
• LIDAR is a technology that uses pulses of laser
  light striking the surfaces of the earth and
  measures the time of pulse return generating
  elevation data points.
• This data can be used to create a digital terrain
  model or DTM. A DTM is a simple digital
  representation of a portion of the earths
  surface.

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Lie of the Land (DTM)
2m Contours (2000)
Lidar Survey (2004)
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LIDAR and Flow Path Modelling
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Data Collection and OLFP Survey Method

• The mapped courses/paths of the OLFP were used by
  a field Engineer to evaluate the impacts of and
  to the OLFP from the built environment. This
  included
• roads
• stormwater infrastructure
• buildings and
• all other major obstructions

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GIS Data Capture Technique

• Cadastral
• Roads
• Aerial Photographs
• Property
• Boundaries
• Stormwater Network
• Wastewater Network
• Parks and Reserves
• Overland Flow Paths

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Detailed Land Use Data

• Land Use data Roads
• Parks
• Buildings
• Imperviousness
• Verges
• Vegetation

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Flow Source From
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House Details Floor Level Flooding
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Site and Boundary Obstructions
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Spill Points
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Spill Points
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The Impact of Roads

• Road Shape
• Intersections
• Catchpits
• Control of Vehicle Crossings
• Berm Shape

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A Tool to Mitigate Effects

• By using the OLFP model and mapping the locations
  where they cross roads or discharge from roads
  the Spill Points can be located across an urban
  area or any other drainage network.
• Providing the opportunity to better plan roads in
  new subdivisions and investigate, designate
  and/or schedule works to mitigate the identified
  adverse affects from uncontrolled (and often
  unidentified) spill points.

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Habitable Floor Flooding
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Potential Habitable Floor Flooding

• Identifying habitable floor level flooding is a
  major outcome of the study. The potential for
  both non and habitable floors to be flooded by
  OLFP is significant.

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Habitable Floor Flooding
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A Tool for Urban Design

• The location and magnitude of OLFPs is a
  valuable information resource that can influence
  the location and design of urban dwellings.
• The detailed OLFP data now available to NSC will
  support better stormwater planning and design and
  urban design in general.
• This in turn will support the more sustainable
  development of NSC.

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Knowledge is Power and Serves Integration

• There is a general unawareness throughout the
  surveyed area of both the threat to property from
  free-flowing water and measures available to
  mitigate that threat.
• It is suspected that unawareness stems from a
  full reliance on the primary piped system and the
  private on-site systems leading to it.
• It is suggested that Council provide an advisory
  service on private drainage issues, options and
  responsibilities.

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Knowledge is Power and Serves Integration

• Developments can be checked at the resource
  consent phase for management of these overland
  flow paths. Ensuring these parts of the
  stormwater system are allowed for in general
• OLFPs can and do impact on the way we live and
  are an integral part of Stormwater Catchment
  Areas. Runoff along OLFPs can flood the floors
  of residential dwellings and damage industrial
  properties.

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A change in approach
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Information management is crucial to achieving
environmental outcomes
In Conclusion

• New technologies are providing the tools to
  collect and use data

LIDAR Survey, Modelling and GIS support delivery
of sustainable outcomes by supporting the urban
planning process.
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Questions