Storm water strategy of Turku City Citywater Storm water expert meeting Turku

Transcription

1 Storm water strategy of Turku City Citywater Storm water expert meeting Turku Olli-Pekka Mäki 1

2 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 estate department, city planning department and environment department, fire department and wastewater management company The strategy was adopted by the City Council in May 2009 Updating of strategy in 2015 because of the changes in storm water legislation Olli-Pekka Mäki 2

3 Background 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.) Esittäjän nimi 3

4 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 and greenery areas Storm water as a resource of landscape planning, in irrigation systems or in management 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 processes Esittäjän nimi 4

5 Actions 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 Esittäjän nimi 5

6 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 Esittäjän nimi 6

7 Is the storm water strategy just a paper in city administration? Esittäjän nimi 7

8 Regional storm water plan Leena Sänkiaho Pöyry Finland Oy Leena Sänkiaho, Pöyry Finland Oy 8

9 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 Leena Sänkiaho, Pöyry Finland Oy 9

10 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 Maastotietokanta Maanmittauslaitos, Leena Sänkiaho, Pöyry Finland Oy 10

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. Arial 20 pistettä, lihavoitu Leena Sänkiaho, Pöyry Finland Oy 11

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 Leena Sänkiaho, Pöyry Finland Oy 12

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 quality made 2011 and Leena Sänkiaho, Pöyry Finland Oy 13

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 Run-off coefficient 0, Leena Sänkiaho, Pöyry Finland Oy 14

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, Leena Sänkiaho, Pöyry Finland Oy 15

16 Plan symbols Preserved open channel Proposals of action Storm water planning Flood issues Prevention of erosion Areas for detention Leena Sänkiaho, Pöyry Finland Oy 16