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Flow Controls & Storage Structures

To limit discharge rates and satisfy LLFA greenfield runoff requirements, you must restrict flow leaving the site and provide volume to store the backed-up water.

Flow Controls​

Flow controls act as bottlenecks in the network. The platform supports several types:

1. Vortex Flow Controls (e.g., Hydro-Brakes)​

Vortex controls are the industry standard for modern SuDS. They utilise complex internal geometry to induce a vortex at high flow rates, artificially choking the flow.

  • Advantage: They can pass significantly more water at lower heads compared to a simple orifice, meaning they require a larger opening for the same design flow. This drastically reduces the risk of blockage.
  • In the Platform: By selecting "Hydro-Brake", you can input your Design Flow (L/sL/s) and Design Head (mm). The backend API directly integrates with Hydro-International's servers to calculate the exact vortex S-curve and model number required to meet your specification.

2. Orifice Plates​

A simple circular hole cut into a plate. The flow rate is governed by the orifice equation: Q=CdA2gHQ = C_d A \sqrt{2gH}.

  • Disadvantage: To restrict flow to low rates (e.g., 2L/s2 L/s), the orifice diameter must be extremely small, making it highly susceptible to blockage by debris.

3. Weirs​

Weirs are typically used as high-level overflows. You can define the crest elevation and length. They are governed by standard broad-crested or sharp-crested weir equations.

4. Pumps​

Pumps discharge a constant flow rate regardless of the upstream head (until the chamber runs dry). They are used when gravity discharge is impossible.

Storage Structures​

When a flow control restricts water, the excess volume must be stored upstream.

1. Crates (Geocellular Storage)​

Underground plastic crates provide high-volume storage in a small footprint.

  • Void Ratio: Typically 95%. This means 95% of the gross volume is available for water storage. The platform automatically accounts for this.
  • Dimensions: You specify the footprint area and the depth. The engine converts this into an explicit depth-area relationship.

2. Ponds & Basins​

Above-ground open storage. Ponds require side slopes (e.g., 1:3 or 1:4) for safety and maintenance.

  • Depth-Area Profile: The platform automatically calculates the increasing surface area at higher depths based on your base area and side slope inputs, correctly modelling the non-linear volume relationship of an excavated pond.

3. Oversized Pipes​

If a site cannot accommodate crates or ponds, the pipes themselves can be oversized (e.g., using 1200mm pipes instead of 150mm pipes) to provide in-line storage volume. The dynamic wave engine natively handles this attenuation without needing explicit storage nodes.