Gravel Addition as a Habitat Restoration Technique for Tailwaters

Abstract

We assessed the efficacy of passive gravel addition at forming catostomid spawning habitat under various flow regimes in the Cheoah River, a high‐gradient tailwater river in North Carolina. The purpose was to provide a case study that included recommendations for future applications. A total of 76.3 m3 (162 tons) of washed gravel (10–50 mm) was passively dumped down the streambank and into the channel in four locations. Gravel sites differed in terms of average reach slope, bank slope, and the initial volume of gravel added, which could have influenced gravel entrainment. Maps of gravel movement under various flows suggested that large‐magnitude discharges (≥113 m3/s) caused extensive migration; however, less obvious, smaller discharges (∼28 m3/s) still caused substantial shifting, which may influence the stability of catostomid spawning substrates. Following gravel addition, the proportion of gravel in the streambed was significantly higher at all gravel sites. However, comparisons of sites to reference stream reaches suggested that sand, gravel, and cobble were still extremely deficient. Additionally, the volume of gravel was inadequate to create gravel depths that provided suitable habitat for catostomid spawning. Although periodic, passive gravel additions may take years to provide suitable spawning habitat for some fish species, we found that river chub Nocomis micropogon utilized the newly added gravel for spawning.

Recognizing gape limitation and interannual variability in bluehead chub nesting microhabitat use in a small Virginia stream

“…Where Nocomis is threatened by anthropogenic alterations (Mammoliti 2002;Kemp 2014;Utz 2014), management goals may include providing minimum flows and/or limiting peak flows during the spawning season (Peoples et al 2014). Similarly, gravel supplementation programs in sedimentstarved tailwaters may need to consider Nocomis substrate preference (McManamay et al 2010). However, as demonstrated in this study, average preferred values may vary annually based on ambient conditions.…”

Direct observations of the effect of fine sediment deposition on the vertical movement of Gammarus pulex (Amphipoda: Gammaridae) during substratum drying

“…Such management strategies should include measures to reduce fine sediment inputs into streams using sediment detention ponds/ wetlands and planting riparian vegetation to stabilise river banks (Verstraeten & Poesen, 2000;Hughes, 2016). Where high river flows are insufficient in flushing fine sediment from streambeds, management techniques such as gravel jetting (Bašić et al, 2017), replenishing depleted coarser grained sediments (Merz & Ochikubo Chan, 2005;McManamay et al, 2010) and the use of instream structures to enhance hydraulic efficiency to transport fine sediments (Palm et al, 2007;Michel et al, 2014) should be considered.…”

Positive biotic interactions in freshwaters: A review and research directive

“…construct large gravel nests for spawning. These nests often occur in large aggregations (Peoples, McManamay, Orth, & Frimpong, ) and usually differ starkly from the surrounding substrate (Bolton, Peoples, & Frimpong, ; Maurakis, Woolcott, & Sabaj, ); chub nests are often the only sources of concentrated, un‐silted gravel in heavily embedded or sediment‐starved reaches during spawning season (McManamay, Orth, Dolloff, & Cantrell, ; Peoples, Tainer, & Frimpong, ). Nest building thus provides critical microhabitat for lithophilic‐spawning fishes, allowing Nocomis and associates to reproduce and persist in reaches of poor substrate quality (Hitt & Roberts, ; Peoples, Blanc, & Frimpong, ).…”