Lecture Nr. 2_August-2024- August KYU.pdf

Hydrology and Water Resources Engineering Lecture Notes

1. TCBE 3106 HYDROLOGY AND
WATER RESOURCES
ENGINEERING

August to December 2024
Year Three, Semester One
Credit Units : 3
Contact Hours: 45

Facilitator
Eng. Dr. Ambrose Mubialiwo

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2. D

Assorted Course Content

Hydrology
Introduction

Hydrological cycle Processes

o Atmosphere and Climate

o Precipitation/ rainfall

o Evapo-transpiration

o Infiltration, soil moisture,

o Subsurface processes

Surface Runoff

o Rainfall-runoff relationships

o Stream flow analysis: Flow direction curves and frequency analysis

o Hydrographs: Instantaneous Unit hydrograph, Unit hydrograph and
hydrograph

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S-

3. un

Course Content
Hydrology

Formulation of Models
o Concept of Liners Reservoir
o Nass and Dooge”s and Kulendaiswamy’s Model
o Mass curve analysis
Flood Considerations: Flood Mitigation and Routing
o Importance of flood studies
o Cause of floods
Flood control measures

Groundwater Hydrology and Hydraulics

o Characteristics of Groundwater

> Occurrence of groundwater

> Groundwater Hydraulics: Darcy’s law

o Steady flow: Simulation of common groundwater problems
o Pumping tests and analysis

o Geophysical methods
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4. A.

Tr

E Course Content
ydrology

Extra Work
o Hydrologic modelling
> Drainage and drainage works

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5. Course Content

Water Resources

Introduction
Water Resources Engineering
Aspects of Water Resources Engineering
o Water Resources Systems
Design of Water Resources Systems
o Approaches of design
Sources of Water
Rainwater harvesting
o Sources water sources; Rivers, Lakes, Streams
o Groundwater sources: Springs and wells
o Water Source Protection
Water Resources Planning and Management
Why plan and why manage?
o Systems Planning Scales
Planning and Management Approaches

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6. un

6.

Water Resourel ourse Content
Irrigation Engineering
Irrigation Methods
Soil water plant relationships
o Crop water requirements
o Design of irrigation schemes
o Sources of water for irrigation: Concrete and embankment dams
GIS & Remote Sensing in Water Resources Engineering
Brief history of Remote Sensing (RS) and GIS
o Sensors systems in Remote Sensing
Remote sensing satellites: Landsat, Gravity Recovery and Climate Experience
(GRCAE) and Indian Remote Sensing Satellite (IRS)
RS & GIS applications in WRE
o GIS components
o Raster data models (Gridded data)
o Vector data models (shaped files-polygons & lines)
o Map projections and systems
o Case study
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7. Course Content
Water Resources

Oil and Gas engineering: Aspects of Water Resources
Basic considerations of oil & gas in water resources
Pollution issues

River Engineering Improvements
Diversion works
Drainage structures
Culverts
Bridges
Dips
o Hydropower Development
Other Structures
o Spillways
Gates and valves

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8. A. HYDROLOGY

Surface Runoff

Formulation of Models

Flood Considerations: Flood Mitigation and Routing
Groundwater Hydrology and Hydraulics

Extra Work

Aaa a

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9. Flood Consideration: Mitigation and Routing

Definition of a flood

=An overflow of a large amount of water beyond its normal limits,

especially over that is normally dry land.

=Flooding may occur as an overflow of water from water bodies in
which the water overtops or breaks levees, such as a dam, river, lake, or

ocean, accumulation of rainwater.

How to mitigate this...

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10. Flood Consideration: Mitigation and Routing

Types of floods
=River Flood
=Flash Flood
=Rain-fed Flood
=Tidal Flood
=Urban Flood
aCatastrophic Flood

=Downstream Flood

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11. Types of floods

Occurs when a river or stream overflows its
banks.

Inundates surrounding area

Seasonal floods are the norm in many rivers, for
example when spring rains or snowmelt increase
the flow.

When river path is changed..

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12. Flood Consideration: Mitigation and Routing

«Flash flood
Is a rapid flooding of low-lying
areas normally occurring when
runoff flows from sleep slopes.

It may be caused by heavy and
abrupt rain associated with, a severe :,.1 ESS
thunderstorm, hurricane,

tropical storm, or melt water from
ice or snow flowing over ice sheets

or snowfields.

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13. Flood Consideration: Mitigation and Routin 1

wRain-fed flood
Caused by rainwater that can’t be !
absorbed quickly enough by
ground
Water accumulates and floods
surrounding areas after a
prolonged rainfall
Note directly related to overflow
or rivers
Common in urban areas with
more impermeable surfaces

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14. Types of floods
Tidal flood
Occur at the coast

Occur when unusually high
tides, combined with strong
winds or storm surges, cause
seawater to overflow coastal
barriers and inundate low-
lying areas.

Can lead to flooding of coastal
roads, homes, &
infrastructure, especially

during extreme high tides

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15. Flood Consideration: Mitigation and Routing
Types of floods

«Urban Flood
« Catastrophic Flood

Downstream Flood

****Course participant to read make notes on the above****

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16. Flood Consideration: Mitigation and Routing
a Causes of Floods

+ The Physical Causes of the Floods:
Presence of a huge flood plain. - flat area of land next to a river or stream
Geographical feature -Heavy rains, especially over the highlands.

o Snowmelt.

Availability of Lakes and Rivers.

o Above average & long period of heavy rain which causes rivers to have

their peak flow at the same time.

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17. Flood Consideration: Mitigation and Routing
a Causes of Floods

+ The Human Causes of the Floods:

o Deforestation increases run off and adds to deposition and flooding downstream.

o Urbanization of the flood plain increases its magnitude & frequency

o Global warming is blamed for sea level rise, increased snow melt &
increased rainfall.

o The building of dams can increase the problem of sedimentation.

o Poorly maintained embankments (levees) leak & collapse in times of high
discharge.

o Increasing population pressure result in sinking of many new wells leading to the
lowering of the water table and the subsequent subsidence of land making it even

more prone to flooding. *****

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18. Flood Consideration: Mitigation and Routing
a Impact of Floods

+ Primary Impact:
o Injury and loss of life.
o Damage of infrastructure.
Debris and sediment to farms, homes, building, railroads, bridges,
road and communication system.
o Loss of considerable soil and vegetation due to erosion and

deposition of sediment in the rural and urban landscape

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19. Flood Consideration: Mitigation and Routing

a Impact of Floods
Secondary Impact:
o Short-term pollution of water in river.
o Hunger and disease
o Fires by short circuit

» Displacement of person who lose homes

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20. Flood Consideration: Mitigation and Routing
a Impact of Floods

+ Tertiary And Long-Term Impact:
o Economic: decline in tourism, rebuilding cost, increasing of food
price due to shortage.
o Urban flooding can lead to chronically wet house, which are linked
to an increase respiratory problems and other illnesses.

o Psychological

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21. Flood Consideration: Mitigation and Routing
a Benefits of Floods

+ Floods (in particular more frequent or smaller floods) can also
bring many benefits, such as:

> Recharging ground water, Making soil more fertile and increasing
nutrients in some soils.

o Flood waters provide much needed water resources in arid and
semi-arid regions where precipitation can be very unevenly
distributed throughout the year and kills pests in the farming land.

o Freshwater floods particularly play an important role in
maintaining ecosystems in river corridors and are a key

factor in maintaining floodplain biodiversity
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22. Flood Consideration: Mitigation and Routing
a Benefits of Floods

> Flooding can spread nutrients to lakes and rivers, which can lead to
increased biomass and improved fisheries for a few years.

> For some fish species, an inundated floodplain may form a highly
suitable location for spawning (fish release eggs and sperm) with
few predators and enhanced levels of nutrients or food.

o Fish, such as the weather fish, make use of floods in order
to reach new habitats.

o Bird populations may also profit from the boost in food production

caused by flooding (WMO/GWP, 2007).

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23. Flood Consideration: Mitigation and Routing
o Floods in Uganda

> Uganda is well endowed with freshwater bodies including major
lakes such Victoria, Kyoga, Edward and George in addition to
numerous streams and rivers whose sources are up in the
mountains of Elgon to the East, Rwenzori to the West and
Muhabura to the Southwest of the country.

o The very presence of these water sources exposes people,
infrastructure and livelihoods to high risk of flooding, particularly
in the March-April-May (MAM) and September-October-

November-December (SOND) rain seasons

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24. Flood Consideration: Mitigation and Routing
a Floods in Uganda

Major Flooding/landslide events in Uganda since 1997

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25. Flood Consideration: Mitigation and Routing

o Floods in Uganda

Major Flooding/landslide events in Uganda since 1997

ND AP Year ND AP
1997 120 153,500 2011 27 63,075
1998 15,200 2012 18 18,432
2001 12 4,166 2013 13 25,445
2002 17 860 2016 15 11,000
2003 25 2,200 2017 17 14
2004 30,000 2018 51 13,000
2006 3 5,680 2019 215 209,553
2007 33 721,045 2020 27 131,500
2008 49 30,040 2021 3 75,134
2010 588 12,795

ND denotes number of deaths and AP stands for number of Affected Populations

Data obtained from Centre for Research on the Epidemiology of Disasters - CRED (2021)

https://www.emdat.be/

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26. Flood Consideration: Mitigation and Routing

2007 - Global Flood Archive - Dartmouth Flood Observatory

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27. Flood Consideration: Mitigation and Routing
a Flood Exposure Worldwide

1789 1800 125 now sew Sew sew or 2SE SE TE IE IE 150 150€

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28. Flood Consideration: Mitigation and Routing
a Methods of Controlling Floods

Structural Method: Protection of the vulnerable area up-to certain

level of flooding. Preferred by engineers and local people.

Non-structural Method: Reduction of loss or damage. Preferred by
social scientists and conservationist.
Integration Method: Integration of structural and non-structural

measures is essential for effective disaster management

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29. Flood Consideration: Mitigation and Routing
a Structural Method

It is a measure to control the physical process of flooding. It also
prevents inundation which protects vulnerable areas up-to certain level
of flooding.

The Structural Options:

Y

Y

Dams and Reservoirs for impounding excess runoff.

Detention basin, Retention Pond to lower the level of flooding

downstream. (Not feasible due to topographical limitation).

Embankment, Dyke, Polder, Levee, or Flood wall to block

the movement of water from rivers to floodplain. (Most preferred option).
Improvement of Conveyance Capacity (Always planned but not done due to
cost element)

Flood by-pass, flood diversion (Not feasible)

Watershed Management and afforestation (rarely or not practiced - MWE
on it)

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30. Flood Consideration: Mitigation and Routing
a Structural Mitigation Measures
227 are of following types:

+ Storage Reservoirs: It is the most effective measure of flood
disaster mitigation measures. The modern reservoirs are mostly
multipurpose. The aim of reservoir is to store excess water during
flood period and release it when flood subsides.

+ Generally, the reservoirs are formed on the upstream of the area to
be protected or on the head reach of the river.

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31. Flood Consideration: Mitigation and Routing
o Non-Structural Method

Measure to reduce loss or damage by administrative measures. It does
not control or affect the process of inundation. It does not foster any
economic growth. It must be linked up with structural measures and
vice-versa.

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32. Flood Consideration: Mitigation and Routing
o Non-Structural Options:

o

o

o

Flood forecasting (done) and warning (poor practice)

Flood fighting (a success around cities)

Flood proofing — water tight windows, doors—building designs..
(traditional practice)

Evacuation and shelter management (a success story....)

o Flood insurance

Floodplain zoning

> Changes in cropping pattern

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33. Flood Consideration: Mitigation and Routing
a Conclusion:

> An area that goes under and remains under water for some times,
is inundation.

o When inundation causes damage to property and crops, disrupts
communication and brings harmful effects to human beings as well
as to flora and fauna, we call it flood.

> Inundation supports fish, navigation, soil fertility, ecosystems,
ground water recharge etc.

> Flood Management measures are aimed at reduction of damage and
harmful effects, and creation of an environment for enhanced
economic activity.

o Urban flood vs. flood in rural areas need to be treated differently.

o Total Flood Control is neither possible nor desirable.

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