I have followed the stories of flooding in the Cowichan Valley and heard about the heavy rains, the high tides and the dikes that have been built.

However, what I have not heard about is the underlying reasons for this flooding. Understanding why this flooding is occurring is the first step in ensuring it doesn't happen again.

Photographs of the flooded area clearly show the floodplain of the Cowichan River and Somenos Creek -- that nice flat land where the houses and sports fields have been built.

The photographs also show the Somenos Marsh area where infilling has been conducted to build schools, shopping areas and recreational facilities.

If one looks at a Google Earth image of the Cowichan River below the upper bridge in Duncan, you can see the unnatural straightness of the channel, as well as the gravel deposits in the area of the confluence of the Cowichan River and Somenos Creek.

You can also see the forest clearing and urbanization of the Cowichan watershed, including the new Cowichan Commons shopping centre and the large bare area on Mount Tzuhalem known as the Cliffs Over Maple Bay.

All these things have contributed to the flooding.

When we fill in our marshlands, we take away the water storage capacity of this land. When we build dikes around floodplain areas, it squeezes the water into a narrower area, causing it to go higher.

When we straighten a river we increase the flow velocities and thus the scouring potential, causing gravel to be moved from the area of straightening to the first open area available. In the case of the Cowichan River, this happens to be at the mouth of Somenos Creek.

When we create impervious surfaces through the development of storm sewers and shopping centres we increase the speed with which the water runs off the land. Clearing forests from the land also increases peak flows. All of this has combined to cause the flooding we see.

It is useful to keep in mind that when we play with nature, nature always has the last move.

Our failure to respect the natural processes and to think we could develop on floodplains with impunity are what really caused the flooding -- not the heavy rains and high tides.

David Polster operates Polster Environmental Services Ltd. from Duncan. He is a plant ecologist who has been involved in reclamation and restoration of degraded sites for 30 years.