Storm water strategy of Turku City
Citywater
Storm water expert meeting
11.12.2014
Turku
Background of storm water strategy
•
Strategy is based on Baltic Sea Challenge Action plan of Turku and Helsinki•
The storm water program was prepared in working group consisting members from waterworks department, real estatedepartment, city planning department and environment department, fire department and wastewater management company
•
The strategy was adopted by the CityCouncil in May 2009
•
Updating of strategy in 2015 because of the changes in storm water legislationBackground of storm water strategy
•
Climate change is predicted to raise the sea level and increase the
amount of rainfall in Northern Europe
•
Sea level rising and increasing amount of storm waters cause
flooding and increase drainage problems in dense urban
environment
•
Storm waters in sewer system cause problems in wastewater
treatment plant and reduce the effectiveness of the purification
processes
•
The groundwater surface levels in urban areas are falling down
because large amount of the coming rainwater are not infiltrating
into the ground due to the land cover changes (paved yards, roads
etc.)
Objectives of Turku storm water strategy
•
Prevent the disadvantages of flooding•
Maintain the ground water levels•
Secure the regional and local drainage of areas•
Prevent the access of harmful substances into storm waters•
Increase the use of surface water elements in planning and construction of parks andgreenery areas
•
Storm water as a resource of landscape planning, in irrigation systems or inmanagement of wetlands
•
Preserve the quality and amount of small ponds, streams and springs•
Reduce the amount of storm water in wastewater networks and treatment plant processesActions of storm water strategy
Targets, procedures and actions were defined for each city
department
•
Master planning
• Storm water management plans based on drainage basins
•
City planning
• Location of storm water management areas in detailed planning • Planning of flood routes, maintenance of natural streambeds etc.
•
Building supervision
• Control and guidance of constructors, local orders for storm water management
•
Environmental protection
• Study of storm water quality
• Municipal orders concerning storm water quality or treatment
•
Waterworks
• Measures to reduct amount of storm water in wastewater sewer network • Prevention of floods in storm water network
Priorities in storm water management
1.
Storm waters are managed and
utilised in the area where they are
formed
• infiltration, leaching beds etc.
2.
Storm waters are led with methods
which are slowering and delaying
flow velocity
• Balancing tanks, dikes etc.
3.
Storm waters are led to wetlands /
basins via green areas before they
are led to stormwater sewer or dikes
etc.
4.
Storm waters are led via storm water
sewers straight to the waterbodies
•
Is the storm water strategy just a paper in city administration?
Regional storm water plan
1.4.2014
Leena Sänkiaho
Pöyry Finland Oy
Basis of the planning
•
Drainage areas
•
Master plan
• In detailed planning it is difficult to observe the whole drainage area
•
The present state of the storm
water management
•
Evaluation of land use changes
•
Proposals for action
•
Plan symbols for the storm
water management
Planning area
•
Turku (122 km
2),
Lieto (25 km
2),
Kaarina (29 km
2),
Rusko (10 km
2) ja
Raisio (27 km
2)
•
Areas on essential
land use change in
Turku
2.4.2014 Leena Sänkiaho, Pöyry Finland Oy 10
2.4.2014 Leena Sänkiaho, Pöyry Finland Oy 11
Drainage areas
•
Rivers: • Ruskonjoki/Raisionjoki, • Paattistenjoki/Vähäjoki • Aurajoki•
Streams: • Kuuanoja• Kuninkoja – Vetikonoja- Saukonoja – Kovasoja • Vähäjoki (Ruskonjoki) • Piipanoja • Topinoja • Lausteenoja • Savijoki • Jaaninoja • Rauvolanoja • Torppalanoja • Ladjakoskenoja
•
Mid-areas•
Arial 20 pistettä, lihavoitu.
•
Arial 20 pistettä, lihavoitu.
2.4.2014 Leena Sänkiaho, Pöyry Finland Oy 12
The influence of land use change
•
The effects of land use
change were estimated to
Run-off coefficients
Ground water areas
Quality of waters
The need of storm water
detention
2.4.2014 Leena Sänkiaho, Pöyry Finland Oy 13
Case Jaaninoja
•
Drainage area 14 ha
•
Rapids in Biolaakso and
Pääskyvuori
•
Restoration of Jaaninoja in
Biolaakso, Munkkionpuisto,
Pääskyvuori and Kurala
areas
•
Kaarninko ground water area
•
Soil is clay, rock and sand on
esker area
•
10 nature protection areas
•
Studies of storm waters
2.4.2014 Leena Sänkiaho, Pöyry Finland Oy 14
Storm water management
•
Problems during heavy rains
at Taalintehtaankatu and
Littoistentie
•
Heavy rains increase run-off
and erosion
•
Ground water is pumped in
Skanssi area
Present state Stream
Drainage area [ha] 1418
• DA in planning area 100 %
Area of covered surfaces [ha]
• Roof area 117,4
• Street area 203,1
Run-off coefficient 0,36
In future
The growth of covered surfaces [ha] 23,9
2.4.2014 Leena Sänkiaho, Pöyry Finland Oy 15
The land use change
•
17 areas of land use change
•
Working and residential areas
•
Run-off coefficient grows only
1 % in the whole drainage
area
•
But on the areas of land use
change from 0,1- 0,42 to
0,2-0,6
2.4.2014 Leena Sänkiaho, Pöyry Finland Oy 16
