Culverts sometimes get plugged especially if there is not maintenance. The "Urban interfaces" in the West are often prone to fire and wildfires can also play havoc with culvert crossings. So, sometimes, in certain environments, it it best to reduce the reliance on culverts. Gravel roads, secondary roads, access roads may be best designed without culverts - which greatly reduces cost, maintenance, and water quality problems. How can reducing culverts lead to water quality? you ask. The answer is in understanding that culverts concentrate water, therefore at the outlets there is often a hydraulic jumb ergo EROSION.
Well, an alternative to culvert crossings are low water crossings. Concrete fords have been used for some time but they are difficult to build, forming and pouring concrete in a channel! Building "hardened crossings" out of rock, that can withstand periodic flooding and high flows, can also be difficult.
One of the techniques we have been using lately is building low water crossings from Articulated Concrete Blocks (ACBs). SWAG (Sacramento Watersheds Action Group), our non-profit, public benefit watershed restoration group, and Salix Applied Earthcare has designed and built several of the over the last few years. We have built them using both Submar ACBs and ArmorLok ACBs (Contech).
We have also been incorporating a Energy Transition System into our Low Water Crossing designs. These transitions systems include a couple of new products, Scour Stop and Green Armor System. These transition systems not only reduce erosion but they are often aesthetically pleasing and can be designed to increase infiltration.
The pictures below show Low Water Crossings built in our local watershed, as part of a 12-year, $1.2 million, grant-funded Sulphur Creek Restoration Projects. Also, Salix has been designing and building similar "crossings" for CA State Parks, Off Highway Vehicle Division to use in the SVRAs (State Vehicle Recreation Areas).
Articulated Concrete Blocks and Low Water Crossings are covered in much greater detail in our 'ACB Episode' - available at the WatchYourDirtStore (www.watchyourdirtstore.com).
For more on this install, check out this previous WatchYourDirt Post.