# Experimental Design of Nature-Based-Solution Considering the Interactions between Submerged Vegetation and Pile Group on the Structure of the River Flow on Sand Beds

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Material and Methods

#### 2.1. Dimensional Analysis

_{50}, ρ, ρ

_{s}, ϑ, ϴ, K

_{ϕ}, m, n, and C

_{d}parameters defined in Table 1 were constant throughout the experiment. The Reynolds number (Re = 4 ρ uA/νP) in all experiments was more than 2000 as the flow regime was turbulent, so the Reynolds number effect was not considered [28]. Froud number (Fr) was obtained using [u/√(4gA/P)]. Thus, in this study, the dimensionless parameters of the variable were regarded as follows in Equation (2):

#### 2.2. Channels and Tools Used

#### 2.3. Hydraulic and Geometric Features

_{sm}is the maximum scouring depth and d

_{0.75}represents the particle size for which 75% of the sediment mixture is finer [31]. Thus, using the above equation and the selected 0.05 m diameter for the piles, the maximum scour depth was 11 cm. The bed thickness was assumed to be 20 cm to make sure the scour did not cover the entire thickness of the bed. Also, a grading aggregate test was performed using standard sieve analysis [32] to determine the sand characteristics used in this research and particle size characteristics. Table 2 shows the geometric properties of the sand sampled in this study. Where d

_{50}represents the median sediment size, the uniformity coefficient is obtained from the ratio d

_{60}/d

_{10}, Dg is the geometric mean size, δg represents the standard geometry deviation, Gr means the coefficient of gradation, and Cu is uniformity coefficient. According to the uniformity coefficient, Cu = 1.133 and d

_{50}= 0.00077 m, the type of bed material was sandy and uniform [32].

#### 2.4. Vegetation Used to Assess the Efficiency as a Nature-Based Solution

#### 2.5. Experiment Design

^{3}. Each measurement point was measured for 120 s, resulting in 24,000 instantaneous velocity measurements. Ideally, ADV measurements should be made in 70–100% correlation. The signal-to-noise ratio (SNR) indicates the strength of the signal received compared to the noise received by the receiver. The amount of correlation indicates the presence of fine particles in the water that scatter sound. The device cannot measure velocity if the water is very clear and smooth, as the signal returned to the receivers is weaker than the noise. Also, the minimum SNR should be 5 or 15 decibels. WinADV software (NORTEK, Rud, Norway) is used to filter the data measured by ADV.

## 3. Results and Discussion

#### 3.1. Scour Depth

#### 3.2. Longitudinal Velocity Profiles

#### 3.3. Vertical Velocity Profiles

#### 3.4. Resultant Velocity Vector

#### 3.5. Turbulence Intensity

_{*}) in a single pile case. Also, the vertical distributions of the longitudinal, latitudinal, and vertical turbulent intensity components normalized by shear stress in a triple pile group with G/D = 2 was shown in Figure 13 (as an example of the triple group pile).

## 4. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 4.**Experiment design. (

**a**) The arrangement of the piles, (

**b**) vegetation used (2 cm height), (

**c**) patched vegetation, (

**d**) overall vegetation, (

**e**) scouring hole, (

**f**) limnimeter.

**Figure 6.**Scouring temporal development for (

**a**) all cases free and with vegetation type 1, (

**b**) single pile, (

**c**) triple pile group with 2D distance, (

**d**) triple pile group with 3D distance, and (

**e**) triple pile group with 4D distance.

**Figure 7.**The values of longitudinal velocity profiles upstream of the first pile (horizontal and vertical axis are dimensionless.).

**Figure 10.**The X–Z resultant velocity vector on the center axis of the channel upstream of the first pile in a single pile case.

**Figure 11.**The X–Z resultant velocity vector on the center axis of the channel upstream of the first pile in the pile group case.

**Figure 12.**The vertical distributions of the longitudinal, latitudinal, and vertical turbulent intensity components normalized by shear stress in single pile case.

**Figure 13.**The vertical distributions of the Longitudinal, latitudinal, and vertical turbulent intensity components normalized by shear stress in the triple pile group with G/D = 2.

Parameter | Symbol | Unit |
---|---|---|

Time | t | s |

Pile angle to the horizon | ϴ | - |

The angle of water and pile contact | K_{ϕ} | - |

Number of piles | m | - |

Number of group piles | n | - |

Piles shape coefficient | C_{d} | - |

Critical deviation of sediment particles | σ | - |

Bed particle diameter | d_{50} | m |

Velocity | U | m/s |

Mass of unit water volume | ρ | kg/m^{3} |

Cinematic viscosity | ϑ | m^{2}/s |

Vegetation height | h_{v} | m |

Vegetation density | dv | % |

Vegetation width to flow width | l_{p} | - |

Scour depth | d_{s} | - |

Depth of flow | H | m |

Channel width | B | m |

Bridge pile diameter | D | m |

Distance of two adjacent piles | G | m |

Gravity acceleration | g | m/s^{2} |

Mass of unit sediment | ρ_{s} | kg/m^{3} |

Channel cross-sectional area | A | m^{2} |

Channel wetted perimeter | P | m |

Parameters | Median Sediment Size | Uniformity Coefficient | Geometric Mean Size | Standard Geometry Deviation | Gradation Coefficient |
---|---|---|---|---|---|

Symbols | d_{50} | Cu | Dg | δg | Gr |

Dimension | meter | dimensionless | dimensionless | dimensionless | dimensionless |

Value | 0.00077 | 1.133 | 0.763 | 1.075 | 1.075 |

Pile Type | Vegetation Type | Vegetation-Free | Type 1 (2 cm-100%) | Type 2 (0.5 cm-100%) | Type 3 (2 cm-50%) | ||||
---|---|---|---|---|---|---|---|---|---|

Ye (cm) | te (min) | Ye (cm) | te (min) | Ye (cm) | te (min) | Ye (cm) | te (min) | ||

Single | Free | 6.5 | 800 | - | - | - | - | - | - |

Overall | - | - | 4.7 | 550 | 5.3 | 711 | 4.6 | 610 | |

Patched | - | - | 4.1 | 550 | 4.9 | 711 | 4.5 | 550 | |

Triple G/D = 2 | Free | 5.3 | 670 | - | - | - | - | - | - |

Overall | - | - | 3.9 | 430 | 4.6 | 490 | 4.9 | 440 | |

Patched | - | - | 3.9 | 610 | 4.9 | 690 | 4.3 | 610 | |

Triple G/D = 3 | Free | 5.9 | 760 | - | - | - | - | - | - |

Overall | - | - | 4.8 | 610 | 5.3 | 760 | 5.1 | 760 | |

Patched | - | - | 4.5 | 760 | 5.2 | 760 | 4.9 | 760 | |

Triple G/D = 4 | Free | 6.2 | 760 | - | - | - | - | - | - |

Overall | - | - | 5.3 | 490 | 5.3 | 760 | 5 | 490 | |

Patched | - | - | 5 | 490 | 5.1 | 711 | 5 | 550 |

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**MDPI and ACS Style**

Miyab, N.M.; Fazloula, R.; Heidarpour, M.; Kavian, A.; Rodrigo-Comino, J.
Experimental Design of Nature-Based-Solution Considering the Interactions between Submerged Vegetation and Pile Group on the Structure of the River Flow on Sand Beds. *Water* **2022**, *14*, 2382.
https://doi.org/10.3390/w14152382

**AMA Style**

Miyab NM, Fazloula R, Heidarpour M, Kavian A, Rodrigo-Comino J.
Experimental Design of Nature-Based-Solution Considering the Interactions between Submerged Vegetation and Pile Group on the Structure of the River Flow on Sand Beds. *Water*. 2022; 14(15):2382.
https://doi.org/10.3390/w14152382

**Chicago/Turabian Style**

Miyab, Nazanin Mohammadzade, Ramin Fazloula, Manouchehr Heidarpour, Ataollah Kavian, and Jesús Rodrigo-Comino.
2022. "Experimental Design of Nature-Based-Solution Considering the Interactions between Submerged Vegetation and Pile Group on the Structure of the River Flow on Sand Beds" *Water* 14, no. 15: 2382.
https://doi.org/10.3390/w14152382