Understanding flow dynamics, especially the transition between laminar and turbulent flow regimes, is crucial for various practical applications in water management systems and industrial processes. In this work, a meticulous study of the flow regime transitions in straight channels was carried out using the Lattice Boltzmann model for shallow water equations (LABSWE), adopting the D2Q9 scheme for domain discretization. The results showed that three fundamental factors were essential in influencing the flow regime: the relaxation time, channel width, and application of external forces. When the relaxation time decreased, a transition was detected from a parabolic velocity distribution (laminar flow) to a logarithmic distribution (turbulent flow). This transition was confirmed by noticeable fluctuations in channel center velocity and increased Reynolds number at reduced relaxation time. Increasing the channel width while keeping other conditions constant showcased the importance of channel geometry in flow dynamics. The narrower channels showed laminar flows, but the flow became turbulent as the width expanded. Additionally, the flow kept its laminar nature in scenarios without external forces. However, when external forces were introduced, the flow regime changed significantly, resulting in a turbulent state.