Flood Risk: What role for natural flood management measures? · 2017-06-29 · • Flood risk...
Transcript of Flood Risk: What role for natural flood management measures? · 2017-06-29 · • Flood risk...
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Flood Risk: What role for natural flood management measures?
G. Pender and C. Morgan
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Legislation
Research Gaps
Gap 5 New studies to improve evidence base
Gap 7 Experimental studies of WWNP
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Riparian Buffer Strips/ Fencing Off
• How it works• Advantages• Disadvantages• Multiple benefits• Where might it be used?
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Storage Ponds
• How it works• Advantages• Disadvantages• Multiple benefits• Where might it be used?
Belford catchment
Stream
Constructed Bund (earth or wood)
Slow release of runoff- over top and from outlet
Overla
nd flow/ ru
noff
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Soil Aeration / Mole Ploughing
• How it works• Advantages• Disadvantages• Multiple benefits• Where might it be
used?
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Tree Planting/ Upland Planting
• How it works• Advantages• Disadvantages• Multiple benefits• Where might it be used?
(SLWCblog, 2014)
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Justifying Investment
• Natural Flood Management (NFM)• Multiple benefit/ Ecosystem approach• We need more evidence and integration of
disciplines
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Evaluation methods
BENEFIT
CATEGORYSPECIFIC RAF BENEFITS VARIABLES LITERATURE
Hydraulics/
Hydrology
• Water storage
• Groundwater recharge
• Disconnection, interception and
attenuation of overland and out-of-
bank flows
• Slow infiltration of stored water-
attenuating peak flows.
• Flood risk reduction properties
- Vol. of water storage capacity
- Time to peak
- Peak/ stage/ bank full discharge
- Manning’s n co-efficient
- Slope (channel and hill slope-
DTM or LiDAR)
- Soil type & structure
- Geology
- Residence time (in RAF)
- Vol. rainfall/ time
- Soil infiltration rate & compaction
- Channel geometry
- Overbank area wetted by flood
- Rate of sediment build up behind RAF
- Land use
- Soil moisture/ groundwater level
- Temp. (water)
- Evaporation rate (diurnal and seasonal)
- Hydrological pathways (seasonal)
- Drainage & irrigation connectivity
(Frontier Economics
Ltd et al. 2013, N
Barber, J and P. F
Quinn 2012, Nicholson
et al. 2012, Owen et al.
2012, Wilkinson et al.
2010b, Wilkinson et al.
2010a)
Ecology/
Habitat/
Biodiversity
• Habitat creation & protection (fish)
• Landscape heterogeneity
• Biodiversity
- Fish species dynamics: age
structure, presence and
population
- Number of fish caught (recreationally)
- Sightings of migratory birds
- Population of migratory birds
(N Barber, J and P. F
Quinn 2012, Morris et
al. 2008, Jonczyk et al.
2008)
Pollution
Control
Sediment
Trapping
• Nutrient cycling- N, P, C, S &
pathogens (denitrification & carbon
sequestration)
• Filtration of diffuse pollution, heavy
metals & contaminants (fertilisers/
pesticides/ herbicides/ pathogens)
• Mitigates periodic nutrient release
incidents
• Improved water quality (likely)
- Soil type/structure/ profile/
distribution/ nutrient retention
capacity
- Soil moisture & chemistry (NH4-N,
NO3-N, PO4-P, pH, N, P, C, K,
Ma, Si, S and Ca)
- Land use & stock density
- nutrient sources- proximity and
connectivity
- Hydrological pathways
- Crop species & cultivation practices
- Organic matter
- N and P export coefficient rates from land use
- N and P annual excretion and defecation rates
from livestock
- Fertiliser/ pesticides/ herbicide application-
type, volumes, concentrations, spatial extent,
timing of application
- Temp. (water and soil)
- Macroinvertebrate indicator species
(Frontier Economics
Ltd et al. 2013, N. J
Barber and P. F Quinn
2012, Fink and Mitsch
2004, Fisher and
Acreman 2004,
Jonczyk et al. 2008,
Nicholson et al. 2012)
Socio-
Economic
• Aesthetic appeal
• Re-use of sediment
• Reduce costs of the impact of
flooding on local communities.
- Equivalent cost of fertiliser for
sediment re-use
- Cost of flood impacts (when they
occur)
- Number of properties at flood risk
- Cost of flood insurance
- Equivalent savings on water treatment due to
improved water quality
No relevant literature
Extensive literature review- variables
Collation of variables into categories
Creation of the navigation diagram
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FLOOD RISK MGMT
How Does it work?
NUTRIENT CYCLING
WATER SUPPLY
WATER QUALITY
WATER CYCLE REGULATION
LANDSCAPE FORMATIONS
FLOOD PROTECTION
FLOOD MITIGATION
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Research Gaps
Gap 5 New studies to improve evidence base
Gap 7 Experimental studies of WWNP
Lack of research on riparian buffers that directly look at hydrology and the
implications for flooding
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Experiment design
RIPARIAN BUFFER
FIELD
STREAM
INRIP CHANNEL
LOGGER HUB
OUTRIP CHANNEL
5m
3.5m
9m
V-channel level sensors (runoff)
Groundwater transducer
Soil moisture probes(Volumetric water content)Stream depth (25m downstream of V- channels)
KEY
217.6mm
220mm
100mm
150mm150mm
120mm
12mm12mm
5 x 1m concrete V-channels
INRIP V-Channel: slope of 186mm over 5mOUTRIP V-Channel:Slope of 245mm over 5m
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CONCLUSIONS
• Buffer reduces runoff more often than not.
• There are “transitional events”: showing a threshold of effectiveness?
• Why is INRIP higher sometimes?
• Relationships/ behaviour between soil and runoff needs further analysis
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Thank You