(Edinburgh-associated) Research Team

Dr. Steve Wallis & Catherine Morgan (PhD student) (Heriot Watt University)

Dr. Kate Heal & Alan Jones (PhD student) (The University of Edinburgh)

Dr. Rebecca Lunn & PhD student? (University of Strathclyde)

Flow and quality issues in SUDS ponds

• Combination of modelling (HWU & SU) and field sampling (EU)

Flow attenuation and dilution in SUDS ponds:Research questions

• How are flow attenuation and solute dilution related to available storage and outlet configuration?

• Mathematical modelling results for pond with v-notch weir at 2m above pond base and various submerged pipes:

• 4 diameters

• 4 elevations

0

0.2

0.4

0.6

0.8

1

0 200 400 600 800

Maximum storage (m3)

Pea

k flo

w r

atio

0.2m pipe 0.15m pipe 0.1m pipe 0.05m pipe

Relationship between peak flow attenuation, storage and outlet configuration; legend - pipe diameter; dashed lines – pipe elevation

Incr

easi

ng

pea

k fl

ow

at

ten

uat

ion 0.5m

0m

1.0m

1.5m

Anomalies

Flow attenuation results

Summary of key issues:

•Peak flow attenuation increases as pipe elevation decreases (more storage available)

•Peak flow attenuation increases as pipe diameter increases (less storage used)

•Two regimes:

weir used – normal

weir not used - anomolous

Flow attenuation results

0

0.2

0.4

0.6

0.8

1

0 200 400 600 800

Maximum volume (m3)

Pea

k so

lute

rat

io

0.2m pipe 0.15m pipe 0.1m pipe 0.05m pipe

Imp

rovi

ng

wat

er q

ual

ity

0m

0.5m

1.0m1.5m

Relationship between peak solute dilution, storage and outlet configuration; legend - pipe diameter; dashed lines – pipe elevation

First flush dilution results

Summary of key issues:

•Peak solute dilution increases as pipe elevation increases (more dilution volume available)

•Peak solute dilution increases as pipe diameter decreases (more dilution volume available)

First flush dilution results

Conclusion:

•Conflict between flow attenuation and solute dilution

Sediment in SUDS ponds:Research questions

• Characterise sediment accumulation and quality in SUDS ponds

• Investigate sediment particle size-metal concentration relationships

• Model sedimentation patterns (and quality?) in SUDS ponds

• Provide recommendations for design and maintenance of SUDS ponds

• Effect of loss of storage on performance of pond

Halbeath Pond

Sediment in Pond 7

Sedimentation patterns and accumulation rates

Effect of surface water management train on sedimentation rate:

– 1.0 cm a-1 in Halbeath Pond (no management train)– 0.4 cm a-1 in Linburn Pond (management train)

1999 2003

Main inflow

Linburn Pond

2003

0

50

100

150

200

250

300

350

400

Halbeath Linburn Pond 7 Wetland

Zin

c (m

g k

g-1 d

ry w

eig

ht)

1999 2000 2001 2002 2003

a

a b,cb,c

a,b

a

a

a,ba,b

a,b

b

b,c

aa,b

b,ca,b

a,ba,b

a

b

Sediment quality results

• Sediment quality “hotspots” in ponds, normally close to inlet.• So far mean concentrations of potentially toxic metals, N, P and

hydrocarbons in Dunfermline pond sediments do not exceed sediment quality guidelines (e.g. Ontario Ministry of Environment Severe Effect Levels), apart from Ni and Cr in Pond 7.

• Mean concentrations close to guideline values for Ni and Cr in all ponds.

Increased metal concentrations

over time

Current work• SUDS pond sediment modelling (advection, mixing, settling)

• Risk assessment of SUDS pond sediments according to land use

• Apply geomorphological principles to model sediment accumulation in SUDS ponds

• Use geophysical methods to survey sediment depths in SUDS ponds

Post-processed 450 MHz ground penetrating radar trace of transect across

the Wetland

Water

Sediment

Depth (m)

1.0 m

0.3 m

0.5 m

0.7 m