This document discusses flood mitigation strategies. It recommends allowing flood plains to function naturally by not building in them and letting flood waters spread out over flood plains rather than being confined to river banks. This helps reduce flood damage, pollution, and erosion. The document also recommends various watershed techniques to retain and infiltrate water such as terracing, cover crops, bio-swales, rain gardens, pervious pavement, and green roofs in order to reduce flood intensity and frequency while improving water quality.

1. F lood m itigation
By:
Mudassar Rehan
(B.ARCH/1003/08)
Alain Ekka
(B.ARCH/1011/08)
Md.Azizullah
(B.ARCH/1033/08)

2. Floods are wate r cove ring p re viou s ly d ry are a.
A flood is a ve ry large am ou nt of wate r th at h as ove rflowe d from a s ou rce s u ch
as a rive r, lake , and oce an.
Th e y can als o h ave ove rflowe d a b roke n p ip e onto a p re viou s ly d ry are a.
Th e d am age s afte r a flood is h ars h b e cau s e e ve ryth ing or p arts of th ings will
b e u nd e r wate r and th e e ffe cts of a flood can kill m any p e op le .
Flood mitigation involve s m anaging th e e ffe cts of flood ing, s u ch as re d ire cting
flood ru n-off, rath e r th an trying to p re ve nt it altoge th e r. It is m anage m e nt of
p e op le , th rou gh m e as u re s s u ch as e vacu ation and d ry/ t p roofing p rop e rtie s .
we

3. F lood ing occu rs in a wid e varie ty of s e ttings :
Riverine flooding
Coastal zone flooding with wave action
High, saturated ground water
Dams and levees breaking
Back up flooding from rivers, creeks, drainage basins
Clogged culverts causing water back up
Back flow from sewer lines
Downhill sheet flow after a heavy rain or snow melt
Roof drainage into the house

4. F lood ing cond itions can b e :
Shallow to deep water
Short warning time
High or low flow velocities
Long or short duration
High rates of rise and fall
Wave action
Debris potential
Hazardous materials in the water
Low-p oint wate r e ntry in th e h ou s e

5. Le t th e F lood P lain b e a F lood P lain
Nutrient rich soils settle out in the flood plain not in the
stream
The easiest way to mitigate flood damage is to let the flood
plain act as a flood plain. When there is more water in the
stream than it can hold, the water spreads out in the flood
plain. As the water recedes, the water in the flood plain
works it’s way slowly back to the river. This is the natural
function of flood plains.
If we try to force the river to stay within the banks during a
flood, the stream cuts down and bank erosion gets worse.

6. Le s s M e s s
Le s s D am age
Le s s Wate r P ollu tion
Allow the flood plain to be a flood plain and do not build
houses, businesses or industries in the flood plain we end up
with less mess, less flood damage and less water pollution.

7. F lood M itigation in th e Wate rs h e d
Reduce:
•Flood Frequency
•Intensity
•Increase Retention
•Increase Infiltration
R e d u ce P ollu tion

8. R e tain Wate r in
Wate rs h e d
Pond
Sediment settles out
Storm Water Retention Basin
Sunlight kills pathogens

9. R e tain Wate r in Wate rs h e d
Sediment settles out
Sunlight kills pathogens
Plants capture nutrients

10. Le t Th e Wate r S oak In
Te rrace s
Keeps sediment and phosphorus in the field

11. Keeps sediment and phosphorus in the field
Cover crops
Nitrogen held in plants
Permanent grass

12. Bio swales
Rain Gardens
Water evaporated through plants
Nitrogen held in plants

13. Pervious Pavement
Less pollution washes off pavement Water evaporated through plants
Green Roofs

14. C onclu s ion
As we work to:
Reduce flood frequency & intensity
Reduce damages from flooding

15. Hold more rain water in the watershed

16. Let the flood plain be a flood plain

17. Improve water quality

18. Th ank you !!!