The constructed stream approach, involves construction of the channel itself and typically the floodplain. Designs may reconnect channel-forming flows to the floodplain either by raising the bed of the channel to the existing floodplain or by excavating the floodplain down to the channel (Figure 8). This approach may include channel shaping such as meanders, riffles, and pools. Channel structures often are used to improve aquatic habitat functionality, grade control and provide bed and bank stability.
These structures include a combination of large rocks and the root masses and trunks from trees. There are numerous methods for determining the criteria for constructed stream design that require a sound understanding of theory and careful consideration of the applicability of the chosen approach to a particular project (Skidmore et al., 2000). The constructed stream approach may be better suited to sites that have stabilized from past disturbances, where past and future land use change is well-known, or where adequate knowledge of sediment transport and fluvial processes are well understood (Nagle, 2007; Neizgoda and Johnson, 2005; Montgomery and Macdonald, 2002). The primary benefit of this approach is that can provide an immediate solution to unstable channel erosion problems.
Constructing and stream channel and floodplain.
A constructed stream several months after construction.
The constructed stream approach requires significantly more engineering and materials costs than other channel enhancement approaches with some construction cost estimates ranging from $100 per linear foot in agricultural settings to more than $2000 per linear foot in urban areas (Malakoff, 2004). Construction costs have increased in the last few years since much more rock is used to build in-stream structures (Nagle, 2007).