Changes in land use on waterways.

One of the problems that land clearing and development produced is the removal of surfaces that can readily absorb and deal with water that falls as rain, with impermeable surfaces.  These can include roads, roofs and footpaths.  Because the water cannot be absorbed it is diverted into stormwater drainage systems.

 

This means that they are subject to short sharp bursts of water flows during and just after rain events.  The water flows are very high but only for short periods of time.

Because they have high flow rates when running, they are often able to pick up sediments and pollute waterways when discharging.




If sediments are being transported in this manner, they can also begin to alter the course of waterways.  In the case below the left side of the creek will continue to erode while the right will have sediment depositing on it.

In addition, pollutants can accumulate on impermeable surfaces, which means that when they eventually are washed into stormwater with rain, they can lower water quality even further.