# The Travel Time of Floatable Litter of Different Densities Influenced by River Flow Velocity
## 3 Results and Discussion
### The Floatable Litter Travel Time with Different River Flow Velocity  
The collected data of FL travel time for different river flow velocities have been analyzed. The results of each FL travel time in three conditions of different river flow velocities have been presented in Table 4. The travel times A, B, and C are represented, respectively. Figure 7 shows a summary of the graphical presentation of travel time for each FL with different densities during three different conditions of river flow velocities. The collected data contained a high variation for the travel time in all conditions. The distributions of FL travel time were statistically significant differences between Condition--A, B, and C, H (3) = 37.365, \(\rho\)! 0.001. This shows that the different values of flow velocity result in the different value data sets for FL travel time. The higher river flow velocity results in a shorter FL travel time. Flow rate determines the fluxes of pollutants in rivers [6; 7; 8], while river flow rate affects river flow velocity [1]. In Condition A, the travel time for each FL is almost the same except for the cloth (FL9) and the cardboard box (FL10). The travel time of FL9 is the longest, T = 82.00 s, as it has the highest density, \(\rho\) = 1154.44 kg/m\({}^{3}\), while FL10's travel time is the second longest despite its low density. Size can be the factor influencing its travel time, as FL10 is the biggest, and most of its area is floating and exposed high up to the atmosphere. The higher the FL area exposed to the atmosphere is, the higher the wind resistance that will act upon the FL. Thus, more wind resistance causes the FL movement to be slower and results in longer travel time. According to [19], the exposed area of litter affects the transportation process. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Condition**} & **Distance** & **Time Taken for a Bottle** & \multirow{2}{*}{**River Flow**} & \multicolumn{3}{c}{**River Depth (m)**} \\ \cline{3-4}  & **between Two** & **to Travel between Two** & **Velocity (m/s)** & **West** & **Middle of** & **East** \\  & **Points (m)** & **Points (s)** & **Riverbank** & **Riverbank** & **Riverbank** \\ \hline A & 5 & 14.307 & 0.297 & 0.824 & 0.472 & 0.19 \\ B & 5 & 25.5 & 0.167 & 0.61 & 0.305 & 0.152 \\ C & 5 & 29.675 & 0.143 & 0.36 & 0.26 & 0.14 \\ \hline \end{tabular}
\end{table} 
Table 3: Parameters required for river flow velocity measurement. In Condition B, FL travel time varies and is mostly longer compared to FL travel in Condition C except for the 0.5 mineral bottle (FL2), body wash bottle (FL3), and slipper (FL17). Turbulence can be the factor causing longer travel time for most of the FL. Turbulence occurs due to the alternating rock densities along a riverbed, where the water will speed up in places with less resistant rocks and slow down over the more resistant rocks. The flow regime at various points along the river is also influenced by the river's cross-sectional shape. The river depth of Sg. Berkelah as the field-testing medium declines along the cross-section. There were many turbulence points observed during Condition B. Moreover, turbulence can also cause the dispersion of FL, which results in longer travel time once it is displaced from the straight path, even though all FL were tossed from the same point. Turbulent flow causes a change in fluid direction and magnitude [20]. The travel time of FL2, FL3, and FL17 is longer in Condition B than their travel time in Condition C. The wind factor can be the reason for the FL moving faster and further when the wind and river flow in the same direction. According to [21], wind factors can cause floating litter