As the water flow progresses downstream, the river channel should become wider and deeper due to lateral and vertical erosion

The rivers discharge will also increase because of the rivers tributaries contributing to the water flow of the main river. These tributaries help collect water from inside the river basin and carry it to the main river where it joins at a confluence.

The gradient of the river will decrease as the water flows further down the river. This is because the gradient is very steep in the Upper Course as the Source is always the highest point. As the water flows down hill from the Source; it cuts down to sea level under gravity before becoming very slow moving when it reaches the mouth to be discharged into the sea or into another river.

The size of sediment will also decrease. The process of attrition causes the sediment to erode and become smaller the further downstream one is as they rub against each other. This is due to rocks of large masses also being large in size. The significance of the mass of the sediment is that it can only be transported downstream if the velocity is large enough to carry it. For example, only a high velocity could carry heavy pieces of sediment. This means that large pieces will be found near to the Source and small ones close to the Mouth.

I have made these predictions from theoretical background into the usual features of a river as so to make accurate predictions.