Why erosion can be called "a sediment spill"

Sediment spilled at the bottom of Edgewood Av, after June 21 storm.

By Jon Standridge

Many of the causes of Madison's sediment problems are similar to the causes of the BP disaster in the Gulf. 

Both oil and mud are very harmful to aquatic ecosystems. Here's a summary from a USGS fact sheet:

Results of a local study "indicated that small construction sites are potential sources of large amounts of sediment erosion. Sediment loads from the two monitored construction sites were 10 times larger than typical loads from rural and urban land uses in Wisconsin."

"When left uncontrolled, large amounts of soil and other small particles collectively called sediment can move off of construction sites along with other attached pollutants. By volume, sediment is the greatest pollutant entering our surface waters, and causes multiple problems."

"Sediment buries plant and animal habitat critical to healthy streams, lakes, and wetlands. Loss of habitat reduces the number, diversity, and productivity of plants and animals living in aquatic environments."

Sediment that remains suspended in the water column reduces water clarity, inhibits aquatic plant growth, lowers the aesthetic and recreational values of water resources, and makes it difficult for some fish to find food.

Suspended sediment increases the solar heating of water, scours aquatic life in streams, and clogs the gills of fish and aquatic insects. Warm water holds less oxygen than cooler water (oxygen is vital to aquatic animals) and increased water temperatures are stressful to coldwater fish such as trout.

Particulate-bound nutrients, such as phosphorus delivered to surface waters by eroded soils, often causes algal blooms and alterations in the food chains, which further reduces the quality of these water resources.

 

Standing in the rotting "delta" at the bottom of Edgewood Av.  It's black, and it stinks.

Some differences between oil and mud

• Oil is more sticky, fouling birds and mammals more than mud. But mud also fouls many aquatic organisms.
• Mud sinks, while oil rises to the top.
• Oil is more toxic.  Yet mud ends up being quite toxic through a chain of cause and effect.  By heating the water and diminishing the oxygen, it can kill fish.  Mud stimulates algae blooms, which can be toxic enough to kill your pet.
• Oil stinks more than mud, but mud stimulates algae, which then dies and rots.

 Because of the similarities between oil and mud, and because big storms dump enough sediment to qualify as a "spill," I'm going to use the term "sediment spill" in future articles.

Mud plume into L. Mendota--it looks like an oil spill.