Features & Attributes of Stormwater Conveyance, Drainage Channels, Stream Banks
Stormwater Conveyance and drainage channels tend to be noticeable within communities and urban areas. These open-surfaced, engineered canals and swales are designed to receive, control and guide water downstream. Concentrated waterways of this kind are capable of handling large, sporadic volumes of water and are highly effective during storm surges. Structures for these applications can be fenced off at the top of the drainageway to prevent objects or people from entering the water channel.
Surface runoff comes mostly via street gutters and underground piping systems, where water is lead to these centralized drainage channels. It is always recommended that the drainage pipes in the retaining wall and clean gravel backfill remain a minimum of 12 inches (300 mm) above the high water mark for any water application, including stormwater drainage channels. This area is wrapped in a filter fabric to prevent fines from migrating into the clean drainage areas.
Stormwater channels are typically formed in canal shapes or with steep streambanks, which are lined with retaining wall blocks to prevent erosion and scouring. Since these retaining walls face tough water application conditions, they may also be further reinforced by geogrid. Another form of conveyance system are step pools, elevated water pools engineered to fill from the top and overflow into the next pool below, thus slowing water speeds and filtering pollutants.
The streambeds of these waterways have riprap or vegetative bases which control water flows. These features act as the first filtration or settling area for sediment sand debris from the infrastructure runoff. Stormwater drainage channels can help treat water and remove contaminants. Cleaner water then flows into larger receiving waters such as rivers, streams or lakes.