Prerequisites
This “course” is designed to be very lean in going through the software requirements to compute and evaluate Pond Storage to mitigate Post-Development runoff.
It is assumed that the learner is practiced in the science and magic of pond design. We don’t discuss any theory here.
This material assumes that the learner is familiar with OpenRoads Drainage, including Layout, Scenarios and Alternatives, Computations and Analysis.
The Data Files
The purpose of this course is to work through the software concepts quickly. The dataset is designed for clarity and speed, rather than realism.
The existing terrain is as hydrologically simple as it can get: a single basin with no runoff from “off-site”.
A simple raised roadway (normally-crowned, curbed), roughly parallels the terrain clear drainage area delineation with no offsite runoff.
The road is in fill and it does block direct overland flow from the north half of the site.
Terrain - Existing
The existing Terrain dgn references a “source graphics” file containing a handful of 3D elements. Most of those elements are horizontal and vertical offsets from the central feature. A change to the central feature propagates to the remaining features. It’s contrived but flexible.
Roadway and Improvements Files
The engineering files follow best practices, being federated and properly linked.
Terrain – Ultimate/Combined
The Ultimate Terrain is a Complex Terrain with the Roadway and Pad surfaces merged into the existing terrain. If the existing terrain or proposed assets are changed, the ultimate terrain updates automatically. Combined terrains are particularly necessary for the OpenRoads hydrology tools, as they do not operate across multiple terrains.
Drainage File
The Drainage file is set up with an Existing and Proposed Scenario and Existing and corresponding Proposed reference files.
References
For the Existing Scenario, only the Terrain-existing reference needs to be on.
For the Post-Development Scenario, the inverse should be true.
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Existing |
proposed |
Existing
A square site, with a single drainage basin – draining to the middle bottom.
Drainage Features include a single Catchment (Grass) and a single, connected Site Outfall structure.
Proposed
Referenced roadway, paved lots and an ultimate surface (existing merged with proposed).
Drainage Features include: Catchments (three Pavements (1 Corridor, 2 Pads) and two Grass Catchments (North and South). All drain to the Site Oufall – so that Pre- and Post- runoff curves can be plotted together.
Pre- and Post-Development Curves
All versions of the _Pond Design.dgn havePre- and Post- Scenarios ready
· The Existing Scenario
o The full site runoff is defined by a single Grass Catchment outflowing to the Site Outfall.
· The Proposed Scenario
o Five Catchments (Two Grass and three Pavements) outflow to the same Site Outfall.