modeling runoff from a green roof · 11 motivation there is a need for modeling tools, able to...
TRANSCRIPT
©C
opyright, G
rontm
ij A
/S 2
011
Grontmij
Modeling runoff from a green roof
Vis
ualis
ering:
Cura
Vita
DBarbara Kleinlercher
©C
opyright, G
rontm
ij A
/S 2
011
Outline
Motivation
Objectives
Theoretical background
Experimental set-up
Results
Conclusions
©C
opyright, G
rontm
ij A
/S 2
011
Motivation
There is a need for modeling tools, able to reproduce green roof runoff
Urban centers: need for sustainable technologies managing
runoff
Odense: more than 35 overflows per year
©C
opyright, G
rontm
ij A
/S 2
011
Objectives
1. Develop and build a mathematical model, able to reproduce rainfall-runoff relationships.
2. Test the model on field data.
3. Examine the impact of green roofs on runoff hydrographs with respect to rainfall depth and initial condition.
©C
opyright, G
rontm
ij A
/S 2
011
Theoretical Background
Identification of dominant processes
Processes:• Rainfall (P)
• Infiltration
• Subsurface flow - subsurface runoff (SSF)
• Saturated surface flow – surface runoff (SF)
• Evapotranspiration (AET)
A. 30mm Sedum-herb-grass had
B. 30 mm Roof soil
C. 40 mm Mineral Wool
D. 0.8mm Root barrier foil
E. Roof
Layering:
• Interception (I)
©C
opyright, G
rontm
ij A
/S 2
011
Theoretical Background
Conceptual model – 2 reservoir model
©C
opyright, G
rontm
ij A
/S 2
011
Experimental Set-up
Measuring devices:• BL1: Level meter • BL2: Level meter • BL3: Level electrode • QX2: Filling valve• QX1: Drain valve• 2 soil moisture sensors
Study Period:April 2009- June 2010
Recorded data:• Rainfall• Runoff• Soil moisture
©C
opyright, G
rontm
ij A
/S 2
011
Results
Experimental Results
Modeling Results
©C
opyright, G
rontm
ij A
/S 2
011
Experimental Results
Retention capacityTotal analyzed rainfall- runoff samples= 56
©C
opyright, G
rontm
ij A
/S 2
011
Experimental results
Retention capacity of the green roof
©C
opyright, G
rontm
ij A
/S 2
011
Detention, runoff and retention
Initially: Dry Total Rainfall 43.2mm7th of June 2010
Initially: Wet Total Rainfall 35.6mm11-12th June 2009
Experimental results
©C
opyright, G
rontm
ij A
/S 2
011
Surface flow does not occur on the roof, since moisture peaks in the soil layer are well defined by one data point and do not stay constant.
Dominant flow dynamics
Experimental results
©C
opyright, G
rontm
ij A
/S 2
011
07/06 08/06 09/06 10/06 11/06 12/06 13/06 14/06 15/060
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
Date [day/month]
Q [
l/s]
07/06 08/06 09/06 10/06 11/06 12/06 13/06 14/06 15/06
0
2
4
6
8
10
12
14
16
Rain
[m
m]
Qobs.
Qsim.
Rainfall: 10 min. interval
• General impression: model overestimates runoff
• Underestimates peak flows
• Nash-Sutcliffe coefficient: 0.44
07/06 08/06 09/06 10/06 11/06 12/06 13/06 14/06 15/060
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
Date [day/month]
Q [
l/s]
07/06 08/06 09/06 10/06 11/06 12/06 13/06 14/06 15/06
0
2
4
6
8
10
12
14
16
Rain
[m
m]
Qobs.
Qsim.
Rainfall: 10 min. interval
Calibration
• Total volume error: 1.78%
Total amount of rainfall: 91mm
Experimental results
©C
opyright, G
rontm
ij A
/S 2
011
Modeling Results
• Peak flow errors: 1.21% to -81.03%
• Volume errors: -32.68% to 21%
• Nash- Sutcliffe: 0.23 to 0.91 -> 3/5 higher than 0.8.
-> Timing and drainage behaviour: very well reproduced
©C
opyright, G
rontm
ij A
/S 2
011
Modeling Results
06:00 09:00 12:00 15:00 18:00 21:000
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
Time [hh:mm]
06:00 09:00 12:00 15:00 18:00 21:00
0
2
4
6
8
10
12
14
16
Qobs.
Qsim.
Rainfall: 10min interval
24/05 31/05 07/06 14/06 21/06 28/06 05/07 12/07 19/07 26/07 02/08 09/080
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
Date [day/month]
Runoff Q
[l/s]
24/05 31/05 07/06 14/06 21/06 28/06 05/07 12/07 19/07 26/07 02/08 09/08
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Rain
[m
m]
Rain: 10 min. interval
Qobs.
Qsim.
• Peak flow errors: -76% to 16.52%• Volume errors: -69.4% to 19.54%
Model validation: 69 days – 34 rain events
• Total volume error: -49.81%
21:00 00:00 03:00 06:00 09:00 12:000
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
Time [hh:mm]21:00 00:00 03:00 06:00 09:00 12:00
0
2
4
6
8
10
12
14
16
Rain
[m
m]
Rainfall: 10min interval
Qobs.
Qsim.
00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00 06:00 12:000
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
Time [hh:mm]
Runoff Q
[l/s]
00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00 06:00 12:00
0
2
4
6
8
10
12
14
16
Rainfall: 10min. interval
Qobs.
Qsim.
©C
opyright, G
rontm
ij A
/S 2
011
Conclusions
Substantial amount of rainfall is stored and evaporated
Layer saturation is the key factor determining retention capacity
A 2 storage linear reservoir model is a promising approach to simulate green roof runoff!
07/06 08/06 09/06 10/06 11/06 12/06 13/06 14/06 15/060
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
Date [day/month]
Q [
l/s]
07/06 08/06 09/06 10/06 11/06 12/06 13/06 14/06 15/06
0
2
4
6
8
10
12
14
16
Rain
[m
m]
Qobs.
Qsim.
Rainfall: 10 min. interval
Total amount of rainfall: 91mm
©C
opyright, G
rontm
ij A
/S 2
011
THANK YOU FOR YOUR ATTENTION!