Direct Rain Investigation and Urban Stormwater Design

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October 6, 2018

Ensembles of peak stormwater runoff from 10% AEP storm events

Use of direct rain for investigation and design of basins and drainage using ARR2016 methods

Presentation by Peter Coombes, Mark Colegate and Sophia Buchanan at Stormwater 2018 conference at 3:45 pm on Wednesday 10 October 2018.

Urban stormwater catchments can be subject to complex hydrological and hydraulic responses driven by unresolved sub-catchment influences, flow pathways and local depression storages.

This paper provides an overview of the processes to define complex urban hydrology, establish evidence based targets for urban catchments and design of detention basins using resources from the revised Australian Rainfall and Runoff guidelines (ARR2016).

Am older urban catchment in Newcastle Australia displayed difficult to define hydrology processes with significant flooding outcomes. Direct rain (rain on grid) processes in combination with Australian Rainfall and Runoff (ARR2016) inputs were used as an investigation method to define catchment storages and surface runoff processes including cross catchment flows. This process permitted a realistic understanding of the urban hydrology and establishment of a realistic coupled 1D/2D model.

The Regional Flood Frequency Estimation (RFFE) model provided by the revised ARR2016 utilises local information within a regional framework to estimate rural peak flows. Given that many urban stormwater management strategies require a no worsening of stormwater peak flows, the RFFE permits evidence based estimates of stormwater runoff targets for design of urban stormwater infrastructure. This investigation utilised rainfall ensembles to design a detention basin to meet the no worsening targets defined by the RFFE and to account for climate change impacts using new methods provided by ARR2016.


Dr Peter Coombes

Dr Coombes has spent more than 30 years dedicated to the development of systems understanding of the urban, rural and natural water cycles with a view to finding optimum solutions for the sustainable use of ecosystem services, provision of infrastructure and urban planning.

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