Evaluation of the Missouri River shallow water habitat using a 2D‐hydrodynamic model

Abstract

Many of the Upper Missouri River dikes have been notched to create additional shallow water habitat (SWH, operationally defined as areas in the stream with depth < 1.5 m, and velocity < 0.75 m s À1 ) for fish populations. The goal of this study was to quantify the additional SWH gained from notching these dikes and to evaluate their performance under different flow conditions. A coupled field and numerical study was performed on a reach of the Missouri River, near Nebraska City, NE, which contains a number of dikes notched in 2004. The numerical simulations showed that the SWH criterion for depth was more difficult to satisfy in the study reach than the SWH criterion for velocity. Notching the dikes resulted in a slight shift of the bankline due to local erosion in the vicinity of the dikes and the formation of scour holes downstream of the notches. Results from the study suggested that notching the dikes had limited impact on the SWH because the area gained from the bankline shift was offset by the area lost from the scour holes formation. The performance of the notched dikes in sustaining the minimum habitat suitability conditions for the Missouri River ecosystem was also investigated. These conditions corresponded to discharges < 709 m 3 s À1 for the period from mid-July to mid-August, or equivalently SWH areas > 5225 m 2 dike À1 during the same period. Analysis of the Missouri River annual discharge records at the study site showed that the dikes can provide the minimum required SWH for mean annual discharges < 667 m 3 s À1 . For mean annual discharges > 667 m 3 s À1 , new alternative structures or restoration facilities were needed, in addition to the existing dikes, to sustain the minimum required SWH. The dikes were not effective in providing any SWH for mean annual discharges > 2000 m 3 s À1 .

Fish Assemblages at Engineered and Natural Channel Structures in the Lower Missouri River: Implications for Modified Dike Structures

“…All physical habitat characteristics associated with an engineered dike structure can be influenced by discharge and flood events (Papanicolaou et al , ). On a broad temporal scale, the physical habitat characteristics are resilient because dike structures are static features (Jacobson et al , ).…”

Selecting Between One-Dimensional and Two-Dimensional Hydrodynamic Models for Ecohydraulic Analysis

“…Many riverine habitat studies and projects require ecohydraulic modelling (Mouton et al ., ; Wu and Mao, ; Hauer et al ., ; Maddock et al ., ). Prescribed flows and restoration designs are often based on and evaluated with these models (Elkins et al ., ; Papanicolaou et al ., ). Models can yield detailed spatial patterns at ‘near‐census’ resolution of ~1 m over tens of kilometres of river corridor length, which can provide advantages over purely empirical assessments (Pasternack, ).…”

Habitat Use by Five Turtle Species in the Middle Mississippi River

“…In addition, false map turtles were captured more often in shallow habitats. Loss of these habitats via sedimentation, dredging, and channel training structures is a concern in river conservation because various fish species, including the endangered pallid sturgeon (Scaphirhynchus albus), need these habitats (Papanicolaou et al 2011). We conclude that loss of shallow, low-velocity habitat could also negatively affect turtle populations of the MMR because habitat use tended to be highest in these areas.…”