and welcome to the February edition of “Keep Things Flowing”, the
monthly newsletter presented by Storm Water Consulting.
In this month’s
newsletter we provide you with some helpful stormwater and flooding
related tips using Brisbane City Council data and we answer another
frequently asked question about undercroft clearance.
Council Helpful Tips
past few months we’ve shared some helpful stormwater and flooding
related tips with our clients and we thought it would be beneficial
for our readers if we were to share these with you too. We’ve
picked three to start off with!
City Council make stormwater pipe information available to the
public through their online eBIMAP2 system. The eBIMAP2 system
provides an integrated map of assets and properties. The eBIMAP2
system is available for access through a subscription based format.
Subscriptions can be bought for a day, week, month or year long
period. Council’s eBIMAP2 system can be accessed using the link
to the daily service which costs $22.60. This allows us to print as
many plans for as many jobs as needed (within a 24 hour period).
City Plan mapping is an interactive mapping system that provides
property information, zoning, overlays, aerial mapping and ground
level information. City Plan mapping is available free of charge
and can be accessed through the link provided below.
City Plan Mapping
Plan mapping is a useful tool when determining whether a property
is located in or adjacent to a Flood Planning Area. To illustrate
the Flood Planning Areas simply search for a property address, open
the “Overlays” tab on the left hand side of the page and expand the
“Flood” category and select through the Brisbane River,
Creek/waterway or Overland Flow categories.
Flood Planning Areas do not necessarily reflect the inundation
expected during a flood event.
property you searched for in the City Plan mapping (discussed
above) is located within a Brisbane River or Creek/waterway Flood
Planning Area, flood level information for the property is provided
by the Council, free of charge. The flood level information is
presented in Floodwise Property Reports, which can be accessed
using the following link.
Floodwise Property Reports
property is located within an Overland Flow Flood Planning Area,
flood level information is not available for the property. A
hydraulic engineer is required to determine the flood level
affecting the property. We would be pleased to provide you with
assistance in determining the overland flow flood levels. Please
contact our office to speak to one of our engineers.
Frequently Asked Question
I plan to
build a dwelling on my property. Using Council’s City Plan mapping
I have identified that the location of the dwelling is within an
overland flow path. Will I have to construct the dwelling on a
suspended floor to allow the overland flow to flow underneath the
dwelling? I need the undercroft height to be as short as possible
due to building height restrictions.
important to remember that the Overland Flow Flood Planning Area
shown on Council’s City Plan mapping is just a tool to indicate
that there could be an overland flow issue on the property. There
is no detailed hydraulic modelling supporting the extent of the Overland
Flow Flood Planning Area. A hydraulic engineer would be required to
determine if and where overland flow is located on the property.
we’ve completed an assessment of the overland flow and found that there
is overland flow at the location of the proposed dwelling. For this
example let’s also assume there is no other solution than to
construct the dwelling on a suspended floor and allow the overland
flow to pass underneath the dwelling. Brisbane City Council’s Flood
Overlay Code requires structures with an undercroft area that
experience overland flow depths up to 0.6m to provide 1.5m of
undercroft clearance (distance between the ground level and the
finished floor level). The purpose of the undercroft clearance
requirement is to ensure debris in the overland flow path would not
get caught on the underside of the structure and block the overland
flow path. Blocking the overland flow path could cause flood level
impacts to the subject site and neighbouring properties. In
addressing the Flood Overlay Code, we have the ability to address a
performance outcome solution and recommend lowering the undercroft
clearance requirement. Supporting a lower undercroft clearance
height is dependant upon the flooding characteristics and site
constraints. An example of supporting a lower undercroft height
could be if the depth of overland flow is 0.2m and the velocity is
very slow. An undercroft height of 1.5m could be excessive given
the flow conditions and other site constraints. If you would like
assistance with determining a suitable undercroft clearance please
contact our office. I link to the Flood Overlay Code is presented
Flood Overlay Code
We hope you
enjoyed this edition of Keep Things Flowing. Feedback on articles
presented is always welcomed and for further information on any of
the articles presented please don’t hesitate to contact our office.
Keep Things Flowing!
The Storm Team
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