1. The Humberside Threat Toby Clark BSc CFIOSH AIEMA
Flooding
The Humberside Threat
Toby Clark BSc CFIOSH AIEMA

2. In England, the most common forms of floods are:
• River flooding that occurs when a watercourse cannot cope with the water draining into it from the surrounding land. This can happen, for example, when heavy rain falls on an already waterlogged catchment.
• Coastal flooding that results from a combination of high tides and stormy conditions. If low atmospheric pressure coincides with a high tide, a tidal surge may happen which can cause serious flooding.
• Surface water flooding which occurs when heavy rainfall overwhelms the drainage capacity of the local area. It is difficult to predict and pinpoint, much more so than river or coastal flooding.
• Sewer flooding that occurs when sewers are overwhelmed by heavy rainfall or when they become blocked. The likelihood of flooding depends on the capacity of the local sewerage system. Land and property can be flooded with water contaminated with raw sewage as a result. Rivers can also become polluted by sewer overflows.
• Groundwater flooding that occurs when water levels in the ground rise above surface levels. It is most likely to occur in areas underlain by permeable rocks, called aquifers. These can be extensive, regional aquifers, such as chalk or sandstone, or may be more local sand or river gravels in valley bottoms underlain by less permeable rocks.

3. Source EA: Flooding in England, a national assessment of flood risk 2009

4. Environment Agency 2008 National Flood Risk Assessment
2.4 million properties at risk of flooding from rivers and the sea in England.
1 million properties also at surface water flood risk
2.8 million properties susceptible to surface water flooding alone
In all, around 5.2 million properties in England, or one in six are at risk of flooding.
The expected annual damages to residential and non-residential properties in England at risk of flooding from rivers and the sea is estimated at more than £1 billion.

5. River flooding
Precipitation on the catchment exceeds drainage capacity.
Extreme rainfall
Narrowing of channel, obstructions, sedimentation
Previously dry weather hardens soil
Peat cutting
Deforestation
Paving over gardens
Flash flooding effect
The Hull floods were of this pluvial nature

6. Coastal flooding
Storm surges due to low barometric pressure ‘humping up’ the sea and wind blown seas
High Spring tides
estuarine narrowing, tidal bores
Rising sea levels (global warming) (expected minimum 1m /100 years – could be as much as 3m!)
Ice melting
Thermal expansion
Isostatic rebound (SE England sinks at 30cm/100years)

8. Glaciers and ice caps
Each year about 8 mm of ocean water falls on the Antarctica and Greenland ice sheets as snowfall. If no ice returned to the oceans, sea level would drop 8 mm every year. To a first approximation, the same amount of water appeared to return to the ocean in icebergs and from ice melting at the edges. There is also evidence of antarctic ice shelves breaking up and accelerating movement of the Greenland ice cap (BBC ‘Frozen Planet’ documentary series no )
High-precision gravimetry from satellites in low-noise flight determined that Greenland was losing more than 200 billion tons of ice per year, in accord with loss estimates from ground measurement. The rate of ice loss was accelerating, having grown from 137 gigatons in 2002–2003.
In 1992, satellites began recording the change in sea level; they display an acceleration in the rate of sea level change, but they have not been operating for long enough to work out whether this signals a permanent rate change, or an artifact of short-term variation.
Source: Wikipedia

9. Sea level rise – flood maps
Environment Agency says 4mm per year on Humberside but recent tides have risen 10cm in 10 years
Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 200 millimetres (8 inches) per century, or 2 mm/year.
Source: Wikipedia

10. Humberside 1m sea level rise
Source: flood.firetree.net

11. Flood maps
Source: flood.firetree.net
Humberside: 2m sea level rise

12. Humberside 3m sea level rise
Source: flood.firetree.net
Humberside 3m sea level rise

13. Environment Agency flood risk mapping
Compare EA risk map with 3m rise map (previous slide)

14. Hull University Campus, 1m sea Level Rise

15. Hull University Campus, 2m sea Level Rise

16. Hull University Campus, 3m sea Level Rise

17. In the summer of 2007 “extreme levels of rainfall” caused pluvial flooding which affected many areas of the UK (Pitt, 2008). In Hull, over people were affected, of whom were forced to leave their homes and live in temporary accommodation (Coulthard et al., 2007).
Despite this, pluvial flooding is not currently considered to be a contingent hazard and is therefore not planned for in the same way as fluvial or coastal flooding.
The floods of the summer 2007 in Hull revealed a certain amount of ambiguity surrounding the responsibility of the institutions involved in flood governance. This study will attempt to map and analyse the complex governance arrangements surrounding flood risk in the north Humber area and critically examine the interaction of government-led and community-led initiatives to reduce flood risk in the area.
Source:

18. Source: Humber Flood Risk Management Strategy – Environment Agency 2008
“We believe that in future we could have difficulty getting funds to improve the defences protecting some of these areas…”

23. References
National flood and coastal erosion risk management strategy for England EA/Defra June 2011
Facing up to Rising Sea Levels RIBA/ICE
Hull Flood 2007 – interim report (Independent Review Body) /8/2007
Humber Flood Risk Management Strategy EA Mar 2008
Govt. Response to Pitt Report Defra Dec 2009
London Strategic Flood Framework (Version 1) London Resilience Team Jan 2010
Flooding in England – A National Assessment of Flood risk EA 2009
Environmental Aspects of Integrated Flood Management WMO Geneva 2006
The Risk of Tidal flooding in London T J Marsh 2004
River Systems & Causes of Flooding Prof S Nelson Tulane Uni. Nov 2011
The Alkborough Tidal Defence Scheme EA