Molonglo 3 East: topography

The topography of Molonglo 3 East demands a reframing of the way planning is done in the ACT. Best practices that apply to the Molonglo valley are not support by the Estate Development Code, Single and Multi-Unit Housing Development Codes, and the zoning codes in the Territory Plan. Molonglo 3 East is something new and exciting that will push ACT planing towards an outcomes planning mechanism.

Related

The importance of the intersection connecting Molonglo 3 East with William Hovell Drive and Bindubi Street is discussed here.

The East West Arterial / bridge and the C10 City to Molonglo Cycleway is discussed here.

The Molonglo 3 East Planning and Infrastructure Study and the reports written by the consultant RobertsDay is discussed here.

The Molonglo 3 East Planning and Infrastructure Study and the reports written by the consultant WSP is discussed here.

Contents

  1. WSP, Outcomes Report, Mar 2021
  2. RobertsDay, Design Principles, Feb 2021
  3. WSP, Options Report, Jul 2020
  4. RobertsDay, Background Report, May 2020
Topographic map of Molonglo 3 East. Map: Cyclosm Data: OpenStreetMap and contribtors.
Coppins Creek Valley shown on a topographic map of Molonglo 3 East. Map: Cyclosm Data: OpenStreetMap and contributors.

WSP, Outcomes Report, Mar 2021

source: WSP, Outcomes Report, Molonglo 3 East Planning and Infrastructure Study, March 2021

Planning

This report will inform a planning study for Molonglo 3 East, with the later development of a Concept Plan for incorporation into the Territory Plan via a Territory Plan Variation.

The planning principles for the preferred Concept Plan Option, influenced by its challenging topography, are not readily integrated into the current Territory Plan – for example the design concept plan does not allocate land uses consistent with current Territory Plan zone nomenclature, which will require resolution within the text of the eventual Concept Plan. A Concept Plan also provides an opportunity to apply novel development assessment requirements through the Territory Plan that can help deliver desired outcomes.
As well, the challenging topography of the site, and the resulting diversity of dwelling typologies in the Concept Plan Option presents challenges for compliance with the Estate Development Code and existing provisions of the Single and Multi-Unit Housing Development Codes. Application of the Code would likely reduce yield and constrain the desired development outcomes for Molonglo 3 East.

Existing Territory Plan controls (including those related to transport, parking, access and mobility; and household trip generation rates), rules and criteria are not consistent with a best-practice urban development of the type envisaged at Molonglo 3 East.

Molonglo 3 East can be a pilot for the required move from existing Territory Plan controls to the application of performance criteria and deemed-to-comply outcomes (which is consistent with proposed ACT Planning system reform) and this is likely essential to achieving the desired outcomes for the site.

WSP, Outcomes Report, Molonglo 3 East Planning and Infrastructure Study, March 2021, 8.

2.1.2 TOPOGRAPHICAL
(see below RobertsDay, Background Report Review, Molonglo 3 East, May 2020)

The site is characterised by significant topography, with an elevation difference of over 100m between the lowest point in Coppins Creek to the highest hilltop on the eastern side of the site.

The infrastructure strategy will aim to maintain and utilise as much natural contouring as possible to fit within the precinct development.

There are distinct hilltops throughout the site that provide opportunities for broad views to the Molonglo River and the mountains. These hilltops present challenges in the large quantity of south facing slope, which cover around 40 per cent of developable area. Within the Estate Development Code, south facing slope puts a limitation on the minimum size of blocks permissible with the existing block compliance tables.

Due to the significant quantity of south facing slope there will be an impact on the available yield allowable under the Estate Development Code.

2.1.3 SLOPE ANALYSIS

Most of the site has falls greater than 8 per cent, with large central portions in excess of 15 per cent.

The steepness of the land will require innovative solutions to the road layout and road types as currently the maximum gradient for a bus route is 8 per cent and maximum on a local street is 12.5 per cent.

The significant slope will require innovative housing typologies to reduce cut and fill on block

WSP, Outcomes Report, Molonglo 3 East Planning and Infrastructure Study, March 2021, 11.

OVERVIEW

The proposed site is approximately 590 ha, with around 480 ha of developable area. The existing topography of the land slopes from approximately RL 630 m to RL 530 m, with a grade averaging between 5–7 per cent. The highest point of the site is amongst the hills located along the eastern boundary. The south-western corner of the site, adjacent Molonglo River is the lowest part of the site. Considerations to the undulating topography has been a key challenge to the infrastructure strategy.

WSP, Outcomes Report, Molonglo 3 East Planning and Infrastructure Study, March 2021, 75.
Ground elevation for Molonglo 3 East with the very deep river corridor (red) and the hills (blue) of the National Arboretum in the middle and Mount Painter left. Molonglo 3 East Future Urban Area (FUA) takes up the central flatter areas. Particularly the central valley along Coppins Creek is very attractive.
Ground elevation for Molonglo 3 East with the very deep river corridor (red) and the hills (blue) of the National Arboretum in the middle and Mount Painter left. Molonglo 3 East Future Urban Area (FUA) takes up the central flatter areas. Particularly the central valley along Coppins Creek is very attractive. An elevation heat map model depicting the contours of the site. Drawing PS119657_CIV_LP003 from the Civil Drawing Package in Appendix D

STORMWATER

The majority of the study area is between 5–7 per cent in grade with the steepest being up to 30 per cent. Provision of new municipal roads with piped stormwater infrastructure will be achievable at these grades, but will need significant engineering inputs, particularly at the detailed design stage. Engineered waterways and swales supporting the piped network through natural drainage areas have been included where possible. …

There has been allowance of significant open greenspace and environmental buffers included throughout the site, with regards to the natural topography of the study area, which further allows for incorporation of site wide stormwater drainage conveyance.
It is proposed that existing overland flow paths be formalised and dedicated as drainage reserves where appropriate, which will be handed over to TCCS as an asset to maintain. This has been coordinated with proposed ecological buffers and park designation where possible. However, a major existing drainage channel flows through the proposed high school location.

Redirection of the channel will involve extensive earthworks, and the channel is suggested to be incorporated into the area as a feature. Comparable stormwater channels have recently been utilised in other schools in a similar manner. …

The greater external stormwater catchment extends into the hilly area to the east of the proposed development (ed. National Arboretum), adding an additional 117 ha of stormwater runoff, with several major gullies conveying the additional stormwater. These external catchments represent approximately 16 per cent of the total runoff flowing thorough the study area, and must be considered when designing infrastructure. The site is further split into 26 existing sub-catchments that eventually discharge to the Molonglo River. …

The proposed development will create new impervious areas within what was a greenfield space. With the addition of this new impervious area, less water is absorbed by vegetation and ground infiltration, which increases the stormwater runoff during rainfall events and can cause stormwater flooding issues if left unchecked. Typical increases in impervious area, such as buildings, car parks and roads are usually mitigated by capture in localised stormwater pit and pipe infrastructure.

However, due to the extensive nature of the proposed Molonglo 3 development area, larger scale treatments need to be considered, and utilisation of the natural topography to convey large water volumes becomes a critical design item.

Grassed swales will therefore be utilised as naturally vegetated engineered controls to the stormwater runoff. These swales will guide the stormwater runoff through the development area while minimising impacts to the proposed developable land.

WSP, Outcomes Report, Molonglo 3 East Planning and Infrastructure Study, March 2021, 79.

Planning Considerations:

TOPOGRAPHY

This report and the Proof of Concept Code Reform Work prepared by Roberts Day in 2019 has discussed the interface between existing Estate Development Code provisions and the topographical conditions of Molonglo 3 extensively. …

This report contemplates a form based approach integrating performance based planning. This is appropriate, but does not sit easily with the rule and criteria format of Codes (with particular regard to the implications of having criteria only controls). …

The proposed replacement of rules and criteria with performance criteria and deemed to comply standards is consistent with proposed ACT Planning system reform, and there is a possibility of Molonglo 3 acting as a pilot in this regard. Irrespective, any rules and criteria should be formulated with a view to their future translation into performance criteria and deemed to comply standards

WSP, Outcomes Report, Molonglo 3 East Planning and Infrastructure Study, March 2021, 86.

RobertsDay, Design Principles, Feb 2021

source: RobertsDay, Design Principles, Molonglo 3 East, February 2021

Movement Corridor Interface: design principle

The Bindubi Street Extension will include the Inter-Town Public Transport Corridor that may include light-rail, rapid bus, or alternative public transport.

The proposed road reserve including the public transport corridor is approximately 3.6kms long and should be designed to promote modal shifts and connectivity within Molonglo 3 East.

In areas of steep topography where the light-rail won’t be able to travel, the public transport corridor should be decoupled from the road reserve corridor.

This will allow it to be built on viaducts or within tunnels if required, without impacting on the road design.

RobertsDay, Design Principles, Molonglo 3 East, February 2021, 160.

Appreciation of maintenance of both types as well as construction costs / urban design impacts and practicality
– Staging of development is a key consideration which may lean toward multiple treatment measures
Topography will play an important role in the location and positioning of WSUD measures
– Gravity systems where possible rather than pumping stations / pressurised mains
– Overland flow and open swales to interface with the urban landscape
– Ensuring adequate space allocation is provided in the streetscape layout and road cross sections

RobertsDay, Design Principles, Molonglo 3 East, February 2021, 168.

Land-use polices

Design principles

– Generally, neighbourhoods should include large shady deciduous trees to reduce the urban ‘heat island’ effect and promote a comfortable walkable neighbourhood
– Residential neighbourhoods that interface with the Molonglo River Corridor should be defined by native landscape where appropriate (open space, buffer zones, etc) whilst including exotic deciduous street trees.
Existing shared use paths within Molonglo district should connect into interfacing neighbourhoods.
– General neighbourhood design should promote health lifestyles and active transport by incorporating street alignment, gradients, connectivity, and wayfinding that assists with non car-based movement.
– Community, recreation, and commercial facilities should be co-located and designed as activity nodes and ‘third spaces’ for public interaction and wellbeing of surrounding neighbourhoods.
The ‘Third Space’ is the social spaces that separate the First Space (Home) from the Second Space (Work). These could include public libraries, cafes, community halls, parks, etc.
– Communities, recreation, and commercial facilities should be centrally located within neighbourhoods and on public transport routes to encourage their role as activity nodes.
– Where located adjacent to green corridors or watercourses, built form should be oriented to natural elements and incorporate them into adjoining public space.
– Commercial, mixed use and higher density residential zoned land should be designed to encourage non car-based trips.
Where possible, commercial and community zoned land is located on land with minimal gradient (less than 5%). Where not possible the built form should relate to the topography and sleeve parking behind active facades
Site specific planning controls should be considered to enable slope responsive dwelling design to enable innovative and sustainable built form outcomes.
Residential subdivision layout should be informed by slope responsive dwelling design of future dwellings and demonstrates ability to accommodate dwellings that achieve reasonable solar access, privacy and size of principal private open space.
Dwelling design should prioritise area and orientation of principal private open space over ground floor access where slope of blocks exceeds 5% grade.
– South facing blocks, and blocks with a northeast/ southwest and southeast/northwest orientation, that are unlikely to achieve a northern orientation for principal private open space, should be located with proximity to public open space suitable for general amenity.
– Street verges should incorporate sufficient area to accommodate street trees to grow to maturity and contribute an urban canopy that is appropriate for the orientation of streets and solar access to associated blocks.
Road design and verges including pedestrian paths should be of sufficient width and grade to promote active travel and accessible movement for people with reduced mobility.

RobertsDay, Design Principles, Molonglo 3 East, February 2021, 175

Over-under terraces

ALTERNATIVE METHOD OF DELIVERING DWELLINGS ON STEEP TOPOGRAPHY

Challenging topography in the northern area of the site requires an alternative housing types. Typical frontages of 10m and block sizes of around 300m².

To allow for equitable access to views and solar access, built form that steps down the hillside is encouraged. The blocks have rear lane access which will require the garage on the upper level of the lower terraces.

Private open space is recommended to be at the upper levels facing north and taking advantage of the views to open space.

RobertsDay, Design Principles, Molonglo 3 East, February 2021, 211.
Over under terraces, Molong 3 East Design Principles
Over under terraces, Molonglo 3 East Design Principles. RobertsDay. Design Principles, Molonglo 3 East, February 2021, 212.

multi-use multi-unit apartment

Multi-unit apartment sites are to be generally four to eight stories.

The bulk and massing of these sites is controlled through the subdivision and mandatory at-grade side setbacks. The smaller footprints enable the buildings to step down the topography to provide equitable views.

RobertsDay, Design Principles, Molonglo 3 East, February 2021, 212.
Mixed-use multi-unit apartment. Molonglo 3 innovation. RobertsDay, Design Principles, Molonglo 3 East, February 2021, 212.

WSP, Options Report, Jul 2020

WSP, Options Report, Molonglo 3 East Planning and Infrastructure Study, July 2020

Topography

Best Use of the Land

Maintaining where possible natural gradients for roads and development
DDA compliance will be required and needs to be considered on paths and pedestrian routes
– Minimising large excavations of cut but where required achieving cut to fill balance
Gradients vary across with majority greater than 8% and in areas in excess of 15%.
Max road gradient for buses 8%
Max road gradient local streets 12.5%.
– Vegetation such as woodlands and environmentally sensitive areas and heritage areas to consideration earthworks and development of lots / roads and infrastructure – how much is cleared or maintained and kept?
By encouraging trails for walkers, bikes and horses, safety with regards to alignment will need to be considered with adequate gradients and steep falls close to features such as Coppins Creek and the Molonglo River / River Corridor.

Corridor Coppins Creek

– Engineering to be sympathetic to the natural state of the creek and maintain the natural features
– Preservation of the river corridor
– Activation of the river corridor and linking previous stages of development along the corridor to the public such as the Namarag Reserve.
– Adequate crossing points for both walkers / riders and vehicles
– Maintaining quality of water within the creek and provide betterment (WSUD principles) where possible
– Potential flooding from Coppins Creek to the proposed surrounding development areas to be considered
– Encroachment within the Coppins Creek flood plain

WSP, Options Report, Molonglo 3 East Planning and Infrastructure Study, July 2020, 264.

RobertsDay, Background Report, May 2020

source: RobertsDay, Background Report Review, Molonglo 3 East, May 2020

TOPOGRAPHY

Southwest of the Molonglo River the site is characterised by mainly undulating land with isolated moderately inclined rolling hills. To the northeast of the river the topography is mainly gently undulating and also has areas of isolated moderately inclined rolling hills. In the north western portion of the site, the Molonglo River is sinuous and deeply incised with the lowest elevation in the study area of 470m. The steepest slopes in the study area are found along the northern reaches of the river with large rocky bluffs up to 60m high and slopes of about 40°.

RobertsDay, Background Report Review, Molonglo 3 East, May 2020, 131.

Landscape and open space principles

• Development responds to topography of the area by minimising cut and fill, responding to key features and minimising the visual impacts of development
• Appropriate buffer areas provided next to existing major roads and development
• River corridor is recognised as an important natural asset to ACT region
• Provision of open space along the Molonglo River, with a balanced range of recreational activities provided appropriate to character of the area
Playing fields provided in central locations, typically co-located with schools to optimise access and usage
• Provision will be made for open space links between Stromlo Forest Park, Molonglo River corridor and the Canberra International Arboretum and Gardens suitable for equestrian, cycling and pedestrian use.

RobertsDay, Background Report Review, Molonglo 3 East, May 2020, 135.

The site is characterised by significant topography, with an elevation difference of over 100m between the lowest point in Coppins Creek to the highest hilltop on the eastern side of the site.

There are distinct hilltops throughout the site that provide opportunities for broad views to the Molonglo River and the mountains. These hilltops present challenges in the large quantity of south facing slope, which cover around 40% of developable area. Within the Estate Development Code, south facing slope puts a limitation on the minimum size of blocks permissible with the existing block compliance tables.

RobertsDay, Background Report Review, Molonglo 3 East, May 2020, 135.

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