Like other water bodies, creeks form in low-lying areas, but unlike lakes, creeks form where there are continuous narrow stretches of low areas called valleys.

Most valleys in the Hamilton area were begun by the movement of glaciers. Glaciers scrape off surface layers of soil and rock as they grow and advance across an area. When they retreat, they leave behind low-lying areas where these materials have been removed. Water drains, or 'runs off', to these areas under the force of gravity and pools. Where there are longer stretches of low land, water flows along, again under the force of gravity, until it is able to escape to even lower land — often through a gap in the landscape.

Areas through which water can flow become eroded over time by that water, creating deeper and deeper channels. If the soil and rock is easily eroded this can occur very quickly. If the underlying material is very hard, it takes longer but still happens. The result is a river valley. Sometimes valleys are called ravines although ravines are usually either very shallow creek valleys or very short cuts in a slope — not long, winding creek paths.

Note the red banks of the Red Hill Creek.

Because creeks have eroded through layers of soil and rock, they expose layers that are not visible elsewhere. Visit the creek nearest to you and, if it is safe to do so, look closely to see what the material in the bottom is like. It may be fine sand, silt or sticky clay. Some local creeks bottoms are quite flat and hard where the surfaces of sedimentary rock layers are exposed.

Creeks are as subject to climatic effects as the land around them, but not in the same way.

When there is a great deal of rain, creeks swell and run more quickly. If the rain is warm the creek temperature may temporarily rise but creeks rarely become permanently warm like ponds can.

In times of low rainfall, some smaller creeks can dry up completely becoming dry creek beds for short periods of time. Some creeks are dry in the winter, especially if there has been little snow and few thaws to melt the snow which does exist. Dry creeks can also be the result of over-extraction of water for agricultural and greenhouse irrigation. Spencer Creek in particular is under this kind of pressure. Creeks that dry up from time to time are called 'ephemeral'.

These ephemeral creeks are still important habitat areas but not over as long a season as creeks that flow more often.