Real-time display of green roof run-off

Real-time display of green roof run-off

This website contains two sets of rainfall run-off data. The original set is for The Mappin Roof for the past two years. This data gives a good initial impression as to the performance of a green roof. The newer data from The Hadfield Roofs offers a comparative look at how different types of vegetation and substrate affect run-off. The interface for accessing both sets of data is nearly identical.

Controlling the Graph Period

Once one of the two data sets has been selected, the tool displays a graph of the last 24 hours rainfall and run-off. This 24 hour period is the default ‘Interval’ and the data can be navigated by interval using the left and right arrow buttons. Left goes backwards in time by one interval, right goes forwards in time by one interval. To start again press ‘Reset.’

If a longer interval is desired (for viewing a longer time period) this can be acheived one of two ways. A new interval can be input directly by using the middle text box and selection between the arrows. Alternatively, by unchecking the interval checkbox, an end date can be selected instead. Pressing ‘Show’ will update the graph to the new period. The arrow buttons will then corrospond to the automatically calculated interval from the manually selected start and dates.

To navigate the data in a different way, clicking the ‘Storm Mode’ check box will disable both interval and end date input modes. Instead, the graph will now automatically focus in on predefined rainfall events. The left and right arrows will go backwards and forwards to the previous or next storm event respectively.

Additionally, there are three other control mechanisms. To zoom in, click anywhere within the graph and drag. A box will appear to show what the new selection will contain. Upon release, the graph will be updated. If a mistake was made, the ‘Undo’ button will restore the graph to its previous state. ‘Zoom Out’ will double the current time interval.

Multiple Roofs

Available only when accessing The Hadfield Roofs. Above the graph small pictures of each roof are displayed. By clicking on up to three roofs, and updating the graph by clicking ‘Show’ a direct comparison can be made. The color surrounding the picture will match the color of the line on the graph.


Several pieces of information about the current graph are tabulated for informational purposes and are displayed in the ‘Statistics’ table. To disable this feature click on the ‘Statistics’ checkbox located on the bottom row to the left of the buttons. The statistics box can also be moved by clicking anywhere within the box, then dragging it to a new location within the browser window.

The information displayed consists of the following information calculated over the duration of the interval:

  • Total Rainfall: The total amount of rain in mm.
  • Peak /min: The peak rainfall flow rate in mm per minute.
  • Mean /60 min: The average rainfall rate expressed in mm per 60 minutes.
  • ADWP: The antecedent dry weather period, the amount of time between a) the start of the graph or b) the start of a displayed storm and the tail end of the previous storm.
  • Storms: The total number of storms detected in the selected interval.
  • Total Run-off: The total amount of run-off in mm.
  • Peak /min: The peak run-off flow rate in mm per minute.
  • Mean 60/min: The average run-off rate expressed in mm per 60 minutes.
  • Retention: The amount of water retained by the roof.
  • Initial Delay: The amount of time bewteen the start of rainfall and the start of run-off in minutes.
  • Peak Delay: The amount of time bewteen the time of peak rainfall flow and peak run-off flow in minutes.
  • Final Delay: The amount of time bewteen the end of rainfall and the end of run-off in minutes.

As these graphs are an investigative tool designed to help explore the potential effects of a green roof installation, there are multiple ways to look at the data. Consistently, rainfall is represented by red on the graph. Blue and other colours on the graph represent how much of the rainfall becomes run-off, going into the drain.

By clicking on one of the following icons, a different format of graph will be displayed:

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