1. Flooding and Its Control
Assoc. Prof. Dr. Tarkan Erdik
Department of Civil Engineering, I.T.U

2. Important notes on flooding
It is acknowledged that there is not a linearly correlation between rainfall and flood events (a 100 year rainfall event will not result in a 100 year flood event).
It is also commonly assumed that the 10-year rainfall will produce the 10-year flood. However, based on research in UK, 140 years rainfall is expected to generate a 100 year flood.
A 500-year flood analysis is required for checking the design of bridge foundations against potential scour failure.

3. Source: Texas Department of Transportation Hydraulic Design Manual, 2006

4. Application and limitation of flood estimation methods

6. Recommended Minimum Stream Gauge Record Lengths
Some of the gauging stations have only staff gauges without authomatic data recording device, and thus data is only recorded one or twice a day. This may lead to missing of the flood peaks.

7. Floods are usually considered in terms of peak runoff or discharge in cubic meters per second (m3/s) and hydrographs as discharge per time.
If a flood has a 20 percent chance of being equaled or exceeded each year, over a long period of time, the flood will be equaled or exceeded on an average of once every five years. This is called the return period or recurrence interval (RI).

8. Up to 5m people in U.K. are at risk from river and coastal flooding
Annual average damage estimated at £0.7 bn
Recent floods have been more frequent
Damage extent exacerbated by:
Extensive building on flood plains
Alterations to riverine channels
Changes in recorded rainfall patterns
Changes in land management use
Climate change expected to increase flooding

9. Flood damage extent often exacerbated by:
River flooding essentially a natural process that helps shape landscape
Flooding generally caused by high rainfall and inability of land to drain water effectively - aggravated further when ground saturated
Flooding frequently leads to serious water pollution and epidemiological problems
Flood damage extent often exacerbated by:
Inadequate flood warning systems
Use of crude hydroinformatics tools
Inadequately trained model users

10. INADEQUATE CAPACITY (WITHIN BANKS) BANK EROSION AND SILTING
CAUSES OF FLOODS
PRECIPITATION
INADEQUATE CAPACITY (WITHIN BANKS)
BANK EROSION AND SILTING
LAND SLIDES
TIDAL AND BACK WATER EFFECTS
POOR DRAINAGE
SNOW MELT AND GLACIAL OUT BURSTS

12. Commercial properties often badly affected by flooding

13. Embankment breaches often cause severe damage

14. Many old bridges throttle flow during floods

15. Single span modern bridges cause less throttling

16. FLOOD PLAIN ZONING WATER SUPPLY III III II I II I FACTORY HOSPITAL
GOVT. OFFICE
POWER HOUSE
PARK
RESIDENTIAL AREA
UNIVERSITY
FREQUENT FLOOD
FLOOD ONCE IN 25 YEARS
NORMAL CHANNEL
FLOOD ONCE IN 100 YEARS

17. FLOOD CONTROL MEASURES
There are various river engineering works that are used, either singly or in combination, to provide flood protection and reduce flood damages along river reaches. These are summarized below.

18. Structural and Nonstructural Measures
Structural measures keep the floods away from resources in the floodplain
Nonstructural measures keep the resources away from floods in the floodplain

19. Structural FRM Measures
Dams
Reservoirs
Floodwalls
Levees
Channels
Straightening
Clearing and snagging
Bridge modifications
Conveyance modifications
Pumping
Channel diversions
Beach Nourishment

20. Structural - Reservoirs
Mt. Morris Dam
McCook, Ill.
FLOOD DAMAGE REDUCTION - Reservoirs
This is the McCook Quarry. Part of the Greater Chicago Tunnel and Reservoir Plan, creating a reservoir here and at Thornton helps ease basement flooding for an estimated 170,000 structures. Construction has not yet started.
Additional Information --
The McCook project was authorized by Congress in 1988 and involves construction of 10.5 billion gallon reservoir in the McCook Quarry. We’re looking at reservoir alternatives. Local sponsor has submitted alternative reservoir plans which Chicago District is evaluating.
Mt. Morris Dam -- In the Great Lakes region, the Mount Morris Dam on the Genesee River, protects the city of Rochester, New York, from flooding. The largest gravity dam east of the Mississippi River, it has prevented nearly $1 billion in flood and erosion damages over the last 46 years.
Also shown are the Center Hill Lake, one of our multi-purpose projects in middle Tennessee, located on the Caney Fork River and Yatesville Lake in Kentucky, our newest flood control reservoir.
Center Hill Lake, Tenn.
Yatesville Lake, Ky.

21. Structural - Walls & Levees
Lock Haven, PA
Frankfort, KY
FLOOD DAMAGE REDUCTION - Walls and levees
We have extensive experience in the design and construction of structural features such as T-walls, I-walls, levees, and closure structures of all kinds. The district presentations will show more detailed examples. The West Columbus project in Columbus Ohio is currently under construction.
Frankfort, KY
West Columbus

22. Channel Modification Projects
Minnesota River, MN, diversion
Martins Fork, KY, diversion
River Rouge, MI, channelization
Harlan, KY, tunnels
LOCAL PROTECTION PROJECTS - SECTION 202
Chronic flooding along the Big Sandy River and Upper Cumberland area, such as this, caused Congress to authorize flood control projects under Section 202 of the Energy and Water Development Act of Whether the construction of floodwalls, gate closures, pump stations, diversion channels or tunnels, Section 202 is helping us relieve many flooding problems. These projects are exempt from normal B/C cost ratio determinations. Planning and Huntington District will speak further on the 202 program.
Additional Information --
Chronic flooding of the Levisa and Tug Forks of the Big Sandy River and Upper Cumberland River, is dramatically illustrated here at Fairview, West Virginia, during the extreme flooding of April The narrow valleys and steep mountains confine all development to the flood plain.

23. Beach Nourishment, (Before) Miami/Dade County, FL
Beach Nourishment, (After) Miami/Dade County, FL

24. Nonstructural FRM Measures
Elevation
Relocation
Floodwalls, Levees and Berms
Buyout/Acquisition
Dry Flood Proofing
Wet Flood Proofing
Flooding Warning/Preparedness

25. Elevating on Extended Foundation Walls

26. Elevating on Fill

27. Elevation on Piers, Posts, Piles, or Columns

28. Relocation Process Moving the Structure Evacuate temporary roadway
Attach structure to trailer
Transport structure to new site

29. Relocation Process Restoration of Old Site
Plan must include a new use for the evacuated floodplain
Demolish and remove foundation and pavement
Disconnect and remove all utilities
Grading and site stabilization

30. Evacuated floodplain area

31. Ring wall/levee

32. Ring wall/levee - closure

33. Ring wall/levee

34. Dry Flood Proofing: Methods
Waterproof Sealant

35. Dry Flood Proofing Method:
Waterproof Sealant

37. Flood Control Measures

38. 1 River Improvement
River improvement is a measure to increase the flow capacity of the existing
river channel and includes widening, dredging/excavation, and dike construction
as illustrated below.
River Improvement

40. A dutch dike
Coastal flooding
Low-lying areas

41. To attain a large flow capacity, widening of the channel is one of the appropriate measures. However, in urbanized area, implementation may be difficult due to land acquisition problem. Measures to reduce peak discharge at the upper reaches of the urbanized area are therefore considered to be necessary
2 Dam
The flood peak discharge is reduced and stored in the reservoir and later released so as to reduce the peak discharge in the downstream. The dam should be situated in a place where large quantity of water will be possibly stored. However, such area is constrained by the topographical and geological conditions of the area

43. 3) Retarding Basin
A retarding basin has the same function as a dam. In general, a
retarding basin is generally constructed in the middle reach to reduce flood
discharge at the downstream reaches.

44. The Watarase Retarding Basin.

45. 4 Floodway
Floodway is aimed at diverting floodwater to the sea, lake or another main river
from the existing river by excavating a new manmade waterway, in order to
avoid the drastic widening of the existing river or to shorten the extension of
improvement

46. Allocation Procedure in Flood Control Planning
In the formulation of a flood control plan, all possible flood control measures/facilities
should be explored and evaluated from the engineering, socio-economic and
environmental viewpoints so as to select the optimum plan.

47. Runoff Model for Alternatives
runoff basin models for SCS unit hydrograph in HEC-HMS window to
obtain the design discharge,
Model for Allocation of Design Discharge
Model for Design Discharge

48. Storm surge barriers
Design & construction
Risk management

49. New York: Verrazano Barrier
Closed
Open

50. Verrazano Narrows Barrier