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Analysis of Low Impact Development
(LID) Strategies using Fully-Integrated
Fully-Distributed Surface
Water/Groundwater Mod...
Ground water and Surface-water FLOW
GSFLOW:
• Based on the USGS PRMS and MODFLOW
• Released in 2008
• Free and open source...
GSFLOW Spatial Conceptualization
Rooftop
Impervious areas &
Depression storage
Pervious area
Tree canopy
(interception)
Mi...
GSFLOW: Cascading Flow Paths
• Allows for a many-to-many
pathway definition
• Runoff and
subsurface/interflow are
routed a...
GSFLOW: Cascading Flow Paths
Accumulated flow
Low Impact Development (LID) Strategies
(CVC & TRCA, 2010)
Select examples:
• Rainwater harvesting
• Green roofs
• Biorete...
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
• Implemented into the GSFLOW code
• Distributed on a cell-by-...
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
input
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
input
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
input
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
D Drainage (specified rate, scheduled rate, or dependent on
mo...
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
D Drainage
E Evaporative loss
E
D
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
D Drainage
E Evaporative loss
Q Overflow
E
D
Q
LIDs: GSFLOW Conceptualization
Manabe (1969) type reservoir
D Drainage
E Evaporative loss
Q Overflow
Smax Storage capacity...
LIDs: Green Roofs
E
Q
E>0, Q>0, D=0
(CVC & TRCA, 2010)
LIDs: Bioswales, Bioretention, etc.
E
Q
Enhanced Grass Swales, Dry Swales, and
Vegetated Filter Strips
E>0, Q>0, D=K
K
(CV...
LIDs: Rain Barrels and Cisterns
Q
E=0, Q>0, D>0
D
LIDs: Infiltration Galleries, etc.
Q
Trenches, and Chambers, and
Soakaways
E=0, Q>0, D=K
K
(CVC & TRCA, 2010)
LIDs: Retention Ponds
E>0, Q=0 (Smax=∞), D>0
D
E
LIDs: Detention Ponds
E>0, Q>0, D>0
D
E
Q
LIDs: Underground rain harvesters
Q
E=0, Q>0, D=D(t)
(CVC & TRCA, 2010)
D(t)
Additional LID Conceptualization:
Permeable Pavement
Achieved by decreasing the (effective)
percent imperviousness
Roof Do...
Case Study: Proposed Town of Seaton
• Proposed Town of roughly 70,000 residents
• Currently agriculture and natural areas
...
Case Study: Seaton Lands
• Complex hydrogeology: 3 Aquifers day-lighting along Duffins
Creek
• Extensive wetland connectiv...
Case Study: Seaton Lands – Current Land use
Case Study: Proposed Development
Case Study: Predicted Drawdown no LIDs (m)
Case Study: Implemented LIDs
• Employment areas: Rooftop capture and 90% of the overflow
being redirected to bioswales;
• ...
Case Study: Infiltration Gallery
Case Study: Infiltration Gallery
• Requires adequate depth to watertable (>2 m)
• Requires a relatively high potential rec...
Case Study: Predicted Drawdown (m)
Case Study: Predicted Drawdown with LIDs (m)
Case Study: Reduction in GW Discharge to
Streams due to Development without LIDs
Case Study: Improvement on GW Discharge to
Streams & Wetlands with LID mitigation
Case Study: Resulting LID-Mitigated Impact to
GW Discharge to Streams & Wetlands
Case Study: Conclusions
With LID implementation:
• Groundwater drawdowns were reduced by 86%;
• Groundwater discharge to s...
In Summary
• Cascading flow routine can allow for any proportion of
generated runoff to be routed to any LID feature
• Ful...
References
Credit Valley Conservation and the Toronto and Region Conservation Authority, 2010. Low Impact Development
Stor...
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Analysis of Low Impact Development (LID) Strategies using Fully-Integrated Fully-Distributed Surface Water Groundwater Models

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Analysis of Low Impact Development (LID) Strategies using Fully-Integrated Fully-Distributed Surface Water Groundwater Models

  1. 1. Analysis of Low Impact Development (LID) Strategies using Fully-Integrated Fully-Distributed Surface Water/Groundwater Models Mason Marchildon Earthfx Inc. IAH 2012 Congress September 18, 2012
  2. 2. Ground water and Surface-water FLOW GSFLOW: • Based on the USGS PRMS and MODFLOW • Released in 2008 • Free and open source • Modular • Fully distributed (Markstrom et.al., 2008)
  3. 3. GSFLOW Spatial Conceptualization Rooftop Impervious areas & Depression storage Pervious area Tree canopy (interception) Micro-topographic depressions • Sub-cell components • Impervious area • Impervious depression storage • Pervious area • Pervious depression storage • Canopy interception
  4. 4. GSFLOW: Cascading Flow Paths • Allows for a many-to-many pathway definition • Runoff and subsurface/interflow are routed along these pathways • The cascade is continued until a stream segment reached or a swale (depression) is reached • Cascading flow will infiltrate downslope if there is available capacity (Markstrom et.al., 2008)
  5. 5. GSFLOW: Cascading Flow Paths Accumulated flow
  6. 6. Low Impact Development (LID) Strategies (CVC & TRCA, 2010) Select examples: • Rainwater harvesting • Green roofs • Bioretention • Permeable pavement • Infiltration galleries • Swales • Etc. Means of stormwater management • Rainfall collection • Runoff reduction • Infiltration enhancement • Evapotranspiration (ET) enhancement (CVC & TRCA, 2010)
  7. 7. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir • Implemented into the GSFLOW code • Distributed on a cell-by-cell basis • Simple design, yet powerful
  8. 8. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir input
  9. 9. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir input
  10. 10. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir input
  11. 11. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir
  12. 12. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir D Drainage (specified rate, scheduled rate, or dependent on model state) D
  13. 13. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir D Drainage E Evaporative loss E D
  14. 14. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir D Drainage E Evaporative loss Q Overflow E D Q
  15. 15. LIDs: GSFLOW Conceptualization Manabe (1969) type reservoir D Drainage E Evaporative loss Q Overflow Smax Storage capacity S(t) Current storage E D Q S(t) Smax 𝑺 𝒕 = 𝑺 𝒕 − 𝟏 − 𝑬 − 𝑫 − 𝑸|𝑺 𝒕 >𝑺 𝒎𝒂𝒙
  16. 16. LIDs: Green Roofs E Q E>0, Q>0, D=0 (CVC & TRCA, 2010)
  17. 17. LIDs: Bioswales, Bioretention, etc. E Q Enhanced Grass Swales, Dry Swales, and Vegetated Filter Strips E>0, Q>0, D=K K (CVC & TRCA, 2010)
  18. 18. LIDs: Rain Barrels and Cisterns Q E=0, Q>0, D>0 D
  19. 19. LIDs: Infiltration Galleries, etc. Q Trenches, and Chambers, and Soakaways E=0, Q>0, D=K K (CVC & TRCA, 2010)
  20. 20. LIDs: Retention Ponds E>0, Q=0 (Smax=∞), D>0 D E
  21. 21. LIDs: Detention Ponds E>0, Q>0, D>0 D E Q
  22. 22. LIDs: Underground rain harvesters Q E=0, Q>0, D=D(t) (CVC & TRCA, 2010) D(t)
  23. 23. Additional LID Conceptualization: Permeable Pavement Achieved by decreasing the (effective) percent imperviousness Roof Downspout Disconnection Achieved by routing impervious runoff to (same-cell) pervious area (CVC & TRCA, 2010) (CVC & TRCA, 2010)
  24. 24. Case Study: Proposed Town of Seaton • Proposed Town of roughly 70,000 residents • Currently agriculture and natural areas • GSFLOW used to test the impact of development and the mitigative effects of LIDs A A’
  25. 25. Case Study: Seaton Lands • Complex hydrogeology: 3 Aquifers day-lighting along Duffins Creek • Extensive wetland connectivity and riparian zones A A’
  26. 26. Case Study: Seaton Lands – Current Land use
  27. 27. Case Study: Proposed Development
  28. 28. Case Study: Predicted Drawdown no LIDs (m)
  29. 29. Case Study: Implemented LIDs • Employment areas: Rooftop capture and 90% of the overflow being redirected to bioswales; • Residential, recreational and school areas : Roof-to-lawn routing of impervious runoff (amount dependent on roof coverage as a proportion of modelled cell); • Unlined (leaky) storm water management ponds; • Infiltration gallery; and • Road side ditches along rural cross sections as opposed to serviced roadways.
  30. 30. Case Study: Infiltration Gallery
  31. 31. Case Study: Infiltration Gallery • Requires adequate depth to watertable (>2 m) • Requires a relatively high potential recharge rates (Iroquois beach deposits 𝐾𝑣 ≅ 1 × 10−7 m/s ≅ 3.3 m/yr) • Needs to be situated in a topographic low to increase contributing area
  32. 32. Case Study: Predicted Drawdown (m)
  33. 33. Case Study: Predicted Drawdown with LIDs (m)
  34. 34. Case Study: Reduction in GW Discharge to Streams due to Development without LIDs
  35. 35. Case Study: Improvement on GW Discharge to Streams & Wetlands with LID mitigation
  36. 36. Case Study: Resulting LID-Mitigated Impact to GW Discharge to Streams & Wetlands
  37. 37. Case Study: Conclusions With LID implementation: • Groundwater drawdowns were reduced by 86%; • Groundwater discharge to streams was increased by 42%; and • Urban runoff generation was reduced by 80% relative to urban development without LIDs
  38. 38. In Summary • Cascading flow routine can allow for any proportion of generated runoff to be routed to any LID feature • Fully-integrated and distributed modeling is required in order to test the feasibility of specific LID strategies, and their local impacts • GSFLOW is Open Source: otherwise this assessment tool would not have been possible
  39. 39. References Credit Valley Conservation and the Toronto and Region Conservation Authority, 2010. Low Impact Development Stormwater Management Planning and Design Guide, version 1.0. 300 pp. Manabe S., 1969. Climate and the ocean circulation 1. The atmospheric circulation and the hydrology of the Earth’s surface. Monthly Weather Review 97(11). pp. 739-774. Markstrom, S.L., Niswonger, R.G., Regan, R.S., Prudic, D.E., and Barlow, P.M., 2008. GSFLOW: Coupled ground- water and surface-water flow model based on the integration of the Precipitation-Runoff Modeling System (PRMS) and the Modular Ground-Water Flow Model (MODFLOW-2005): U.S. Geological Survey Techniques and Methods 6-D1, 240 pp. For more on GSFLOW: TH1-B: E.J. Wexler, Jacek Strakowski, Dirk Kassenaar, Mason Marchildon, Pete Thompson & Rich Niswonger. Integrated Groundwater-Surface Water Modelling with GSFLOW in a Complex Watershed on the Niagara Escarpment TH2-A: Dirk Kassenaar, Mason Marchildon & E.J. Wexler. Rethinking recharge For more on Urban Hydrology: F3-G: Peter J. Thompson & William K. Annable. Characterizing change in baseflow interactions with urbanization through event-based hydrograph separation and analysis

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