The hydraulic geometry of tidal inlets, like, cross-sectional area, wetted perimeter and hydraulic gradient is controlled by the dynamics of tides and wave-induced littoral drift along coastlines, pushing materials into the inlet during the flood tide and flushing them out during the ebb tide. An inlet which maintains its hydraulic stability has its velocity so adjusted that it can flush out all the materials pushed into the inlet. The Pichaboni inlet situated along the Bay of Bengal coast, is a linear channel and the tidal inflow is restricted by a sluice gate. This paper investigates the impact of hydraulic geometry, morphological changes and tidal behaviour on the hydrodynamic stability of the Pichaboni inlet. The longitudinal profile shows a reverse gradient from sea to inland. The smallest cross-sectional area (throat cross-section, $A_{\mathrm{C}}$) is located 672 m inland, which is slightly smaller than the cross-sectional area required to maintain the equilibrium flow velocity. Hence, the actual flow velocity through the throat cross-section is greater than that required for the equilibrium state, and the enlargement of the cross-section area may be caused by sediment scouring which decreases the flow velocity and leads to shoaling at the mouth. The dominant west to east longshore transportation brings a huge amount of sediment influx responsible for continuous sedimentation and the associated formation of spit at the inlet mouth. Any constriction at throat due to spit formation leads to accelerated flow velocity associated with scouring at the throat area and breaching of the spit. This results in the gradual shifting of the inlet mouth by the mechanism of bar by-passing. The economic importance of the main inlet channel and its adjacent intertidal basin necessitates evaluation of the long-term stability of the tidal inlet through analysis of hydraulic and sedimentary characteristics of the inlet.

潮汐入口的水力几何形状，如横截面积、湿周和水力梯度，受潮汐动力学和沿海岸线波浪引起的沿海漂移的控制，在涨潮期间将物质推入入口并在涨潮期间将其冲出大浪淘沙。保持其液压稳定性的入口的速度经过调整，可以冲出所有推入入口的材料。Pichaboni 入口位于孟加拉湾沿岸，是一个线性通道，潮汐流入受到闸门的限制。本文研究了水力几何、形态变化和潮汐行为对 Pichaboni 入口水动力稳定性的影响。纵向剖面显示了从海洋到内陆的反向梯度。最小截面积（喉部截面积，${\mathrm{一种}}_{\mathrm{C}}$) 位于内陆 672 m，略小于维持平衡流速所需的横截面积。因此，通过喉道横截面的实际流速大于平衡状态所需的流速，横截面面积的扩大可能是由于沉积物冲刷导致流速降低而导致口部形成浅滩。占主导地位的西向东沿岸输送带来了大量的泥沙流入，导致连续沉积和在入口处形成相关的吐痰。由于唾液形成而在喉咙处的任何收缩都会导致与喉咙区域的冲刷和唾液破裂相关的流速加快。这导致通过棒旁路机制的入口口逐渐移动。