Urban Water Management and Soils (ESRM 311 & SEFS 507)

Transcription

1 Urban Water Management and Soils (ESRM 311 & SEFS 507) Cougar Mtn Regional Wildland Park & Lakemont Blvd, Bellevue WA Lecture Today Some Urban Water management terms Examples of water management in urban areas Field trip sites 1

2 Urban Water Management terms A retention basin is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. Sometimes called a wet pond or wet detention basin, it is an artificial lake with vegetation around the perimeter, and includes a permanent pool of water in its design A detention basin, sometimes called a "dry pond," which temporarily stores water after a storm, but eventually empties out at a controlled rate to a downstream water body. Infiltration basin which is designed to direct stormwater to groundwater through permeable soils 3 Urban Water Management terms Stormwater management pond is an artificial pond that is designed to collect and retain urban stormwater. They are frequently built into urban areas in North America to also retain sediments and other materials Stormwater detention vault is an underground structure designed to manage excess stormwater runoff on a developed site, often in an urban setting. This type of best management practice may be selected when there is insufficient space on the site to infiltrate the runoff or build a surface facility such as a detention basin or retention basin. Detention vaults manage stormwater quantity flowing to nearby surface waters. They help prevent flooding and can reduce erosion in rivers and streams. They do not provide treatment to improve water quality, though some are attached to a media filter bank to remove pollutants 4 2

3 Bioretention Basins Bioretention basins are landscaped depressions or shallow basins used to slow and treat on site stormwater runoff. Stormwater is directed to the basin and then percolates through the soil and plant system where it is treated by a number of physical, chemical and biological processes. The slowed, cleaned water is allowed to infiltrate native soils or directed to nearby stormwater drains or receiving waters. 5 Water Management terms Specifically: Bioretention is the process in which contaminants and sedimentation are removed from stormwater runoff. Stormwater is collected into the treatment area which consists of a grass buffer strip, sand bed, ponding area, organic layer or mulch layer, planting soil, and plants Bioswales are landscape elements designed to remove silt and pollution from surface runoff water. They consist of a swaled drainage course with gently sloped sides (less than six percent) and filled with vegetation, compost and/or riprap. The water's flow path, along with the wide and shallow ditch, is designed to maximize the time water spends in the swale, which aids the trapping of pollutants and silt. 6 3

4 or Grassed Swales A grassed swale is a graded and engineered landscape feature appearing as a linear, shallow, open channel with trapezoidal or parabolic shape. The swale is vegetated with flood tolerant, erosion resistant plants. Rain Gardens A planted depression or a hole that allows rainwater runoff the opportunity to be absorbed from impervious urban areas, like roofs, driveways, walkways, parking lots, and compacted lawn areas, Reduces rain runoff by allowing stormwater to soak into the soil (as opposed to flowing into storm drains and surface waters which causes erosion, water pollution, flooding, and diminished groundwater). can be designed for specific soils and climates The purpose of a rain garden is to improve water quality in nearby bodies of water. Rain gardens can cut down on the amount of pollution reaching creeks and streams by up to 30%. Flat curbs contain asphalt but allows water to flow into the rain garden

5 Green Roofs (or rain gardens???? with shallow soils) Green roofs or vegetated roof covers (also referred to as living roofs, nature roofs and eco roofs) are a thin layer of living plants growing in soil on top of a roof. Iceland Iceland lkit/greenroofs.html Chicago City Hall Green Roof 9 Seattle green roofs 5

6 Underground Storage (vaults) On site, underground stormwater retention /detention accomplishes the capture and storage of stormwater collected from surrounding impervious areas Pervious Pavement Pervious pavement is designed to allow percolation or infiltration of stormwater through the surface into the soil below where the water is naturally filtered and pollutants are removed. Types of pervious pavements: Poured in place pervious asphalt Poured in place pervious concrete surfaces Block and concrete modular pavers Grid pavers made from either recycled plastic or concrete

7 Green Stormwater Infrastructure (GSI) The High Point Redevelopment Project in West Seattle combined street side bioretention swales with compost amended soils over the entire site (34 city blocks). Performance of the bioretention swale filtering and infiltrating street runoff during a 100 year storm event is shown in photo on the left. Bottom photo shows the development of a retention pond. organics make splash in green infrastructure/ 13 Parking Lot Filter Strips Filter strips are gently sloping, vegetated areas adjacent to impervious surfaces. They are intended to reduce impacts of sheet flow and velocity of stormwater and help improve its water quality urban filter strips are thought capable of removing a minimum of 35% of solids and 40% of nutrients. pollutant removal appears to depend on the width of the filter, a 150 feet wide strip being superior to a 75 feet wide strip

8 King County Parks Cougar Mt Regional Wildland Park on Cave Hole Trail (Alderwood and Beausite soil series) #1 15 Black Forest Biochar soil amendment & art!! Hans Baumann is creating an art installation at Cougar Mountain Wildland Park. From 1863 to 1963, this park was the site of intensive coal mining and logging, and it is estimated that some 29,930,000 tons of CO₂ were emitted into the atmosphere as a result of these activities. Black Forest (29,930,000 tons) will reimagine the park as a site for carbon sequestration through the construction of a large scale land art installation. The project entails covering a carefully selected site in the forest with biocarbon an environmentally benign charcoal that is uncannily similar in appearance to the coal that was once mined there and still litters the forest floor in some places. 8

9 Lakemont Highlands Park, Bellevue WA #2 #1 17 Lakemont Highlands Park, Bellevue WA (playgrounds?) 18 9

10 Lakemont Highlands Park 19 Lewis Creek Picnic Shelter, Bellevue, WA 20 10

11 #3 Lewis Creek Picnic Shelter, Bellevue, WA 21 Lewis Creek Picnic Shelter Bellevue, WA 22 11

12 Lakemont Blvd Retention/Detention Ponds, Bellevue WA #4 23 Lakemont Blvd SE Bellevue, WA 24 12