Key watershed processes

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In a previous post, I identified key watershed areas.  This posting covers important processes that happen at many locations in the watershed.   Each instance may be small, but together they add up to a significant concern or opportunity in the watershed.

All of these would make good volunteer projects.  Look for ones that apply to your neighborhood, find a few people to help, and get started!  Let the Friends of Lake Wingra know about your project-they may be able to help.  Click on the photo examples below, to enlarge them.

Improved infiltration for grassy swales--the greatest opportunity

Midvale School during storm


Athletic fields at schools typically have swales around the borders, and sometimes down the center.  The swales deliver runoff from the entire field to stormwater inlets that are flush with the ground surface.

The infiltration potential of these swales could be easily enhanced by...

• Creating a series of low dams, simply by removing squares of turf in the swales, and using these squares to build a series of check dams one or two layers of turf high.
• Planting the swales with attractive prairie vegetation, such as cup plant.  Research has demonstrated that prairie vegetation promotes substantially more infiltration, compared to turf.

• Placing a "collar" about a foot high around the stormwater inlet, so that storage pool is created around the inlet.  This would increase infiltration, store floodwaters, and filter stormwater going into the inlet.

Similar swales are widespread, found in parks, golf courses, medians of streets, bordering the beltline, and between houses or businesses.

Sidewalk "rivers"Midvale Blvd below school

Some sidewalks, usually on hills, can become substantial rivers of runoff.  Usually sidewalks are sloped towards the street, and so the "sidewalk rivers" empty to the street at the first driveway.

But in some areas along parks or schools, these rivers run for a long distance.  Rain gardens--located at the bottom of these sidewalk rivers--could capture substantial runoff.   The logical place for these rain gardens is on the terrace--and in some locations, a segment of the street's parking lane could be reconstructed to accommodate a larger rain garden.

School and church parking lots

Queen of  Peace parking

These often are very large, and have obvious places at their border where rain gardens could be built.

Those that don't drain to the edge present more of a challenge.  If you observe during a storm, it's possible to find locations within the lot where gardens could be built--sacrificing only a few parking spaces.

Rain gardens in streets

Street gutters obviously collect substantial runoff.  Terrace rain gardens have limited potential to absorb street runoff, because terraces are too narrow, or too high above the street, or because the inlets become clogged.

Therefore, the parking lane of some streets should be turned into rain gardens (short segments only). 

Cherokee and Chippewa drives are quiet residential streets with little traffic, situated at the bottom of ravines. Steep side streets deliver runoff straight to the flumes running down the medians of these streets.

If rain gardens were constructed at intervals in parking spots of these two streets, the gardens would intercept the runoff from side streets before delivering it to the flumes.  This would capture debris before it clogs the flumes, and help moderate the flooding downstream.  (Steve Arnold's idea).

Key infiltration areas

These swales and sidewalk rivers mentioned above--are "key infiltration areas."  These are areas that present especially good opportunities for infiltration, because of certain characteristics...

• They collect runoff from larger areas.
• Located above the water table, or over sandy deposits.
• Owned by City, or by an entity likely to cooperate
• Minimal danger from overflow of runoff
• Addressing runoff here may solve another problem, such as icy patch on sidewalk

FOLW should work for a City policy that any redevelopment will take full advantage of these key areas.

Besides the swales, parking lots, and sidewalks mentioned above, here are other key infiltration areas: 

• Depressions along Schroeder Rd.
• Depression at NE corner of Edgewood Campus.
• Odana Golf Course and surrounding woods
• Glenway Golf Course
• Arbor Hills greenway

Dams in drainage ways

Ditch along bikeway W of Midvale

Swales grade into drainage ditches.  Because ditches are fairly deep, they represent an opportunity to slow and store runoff.  A series of check dams along ditches would do the trick.  They could be composed of gravel, Deltalok bags, or metal.

The growth of native vegetation in drainage ditches should be encouraged (unless that particular ditch has a tendency to overflow).  Vegetation slows the flow, absorbs water, and infiltrates it.

When the Parks Dept. cut saplings growing in the N-S drainage way in the Glenway Woods, it encouraged the growth of invasive burdock and Japanese knotweed.

Leaching organic waste

There are a number of filters or basins that trap leaves on their way to the lakes.  For example, at the bottom of the new Pickford St. box culvert, where it crosses Arbor Dr., you can look down through a grate and see a stinking mass of brewing organic waste.  This" leaf tea" should be cleaned out on a frequent basis.

Uncovered dumpsters

A recent survey of "watershed awareness" at schools revealed that about half had dumpsters with open lids.  Besides tempting wildlife, open dumpsters can create toxic lechate, which then washes to the storm sewers.

Improper salt storage

...as been identified at two locations in the area, in Westgate Mall, and the World Council of Credit Unions (right).




Eroding terraces

Under heavy shade, grass won't grow on terraces, leading to erosion.  Often this is aggravated by heavy runoff from sidewalk rivers.  This can easily be corrected by planting shade-tolerant native plants on the terraces.

Eroding slopes and paths

Two examples are the pathways in the Glenway Woods (right), and the path in Nakoma Park from Thoreau School to the park.  Solving these requires two things: solving the runoff issue, and then reconstructing the pathway. 




Unpaved drives and alleys

Examples:  The steep maintenance road on the Edgewood Campus (right), and unpaved alleys parallel to Monroe Street.

Salt overspreading leads to erosion

When de-icing salt is spread beyond the sidewalk, it kills the grass.  Next spring, the ground starts to erode.  Repair involves spreading fresh dirt along the sidewalk.  But this erodes in the next rain, due to runoff channeled by the sidewalk.  Examples are sidewalks along Hilldale Mall (right), Queen of Peace Church, and Westmorland Park.  More photos.


Leaves in gutters/Clogged stormwater inlets

This leads to leaves washing into the lakes, or stormwater overflowing the land, leading to erosion.  Terrace rain gardens won't function if their inlets are clogged.  Citizens need to take responsibility for keeping their leaves on the terrace, and clearing the inlets in their neighborhood.

Overdrive by maintenance vehicles

Tractors--clearing sidewalks during winter--don't keep their tires on the sidewalk.  Are the tractors too wide for the sidewalk?  This leads to muddy trenches along the sidewalk, then to erosion.

Streets without curbs

In the Sunset Village and Westmorland neighborhoods, many streets don't have curbs.  Cars park with one wheel on the terrace.  This leads to muddy ruts, then erosion.  It's ugly.

This can easily be fixed with "do-it-yourself" curbs made of landscaping timber, or of rocks.   Either repair looks "rustic" and preserves the country ambience of the neighborhood.  FOLW could encourage terrace repair by handing out informational brochures to homeowners with a terrace problem.

Abused terraces in these neighborhoods could also be turned into rain gardens, which would accept street runoff.  Prime examples are curbless streets like Meyer St (right).


Eroding streambanks/damaged flumes

Examples: Nakoma Park open stream (right),





The flume in Chippewa Dr(right),

flume leading to Odana Pond, and drainage way just east of Wright Middle School (right).


Sidewalk puddles

Places where water pools on sidewalks become icy hazards for pedestrians in winter.  These are also prime locations for small rain gardens on terraces.