eChapters

Flood-control measures aim to reduce the probability of inundation or limit its harmful consequences. Structural measures physically modify water flow or storage and include dams, reservoirs, levees, floodwalls, diversions, channel improvements, detention basins, and watershed-treatment structures. Non-structural measures reduce exposure and vulnerability through forecasting, warnings, zoning, insurance, preparedness, evacuation, public education, land-use control, and disaster-response planning. This chapter classifies and evaluates both groups of measures, explaining their purposes, benefits, limitations, and selection criteria. It emphasizes that no individual intervention provides complete protection. Effective flood-risk reduction normally requires an integrated combination of structures, sound watershed management, reliable information systems, institutional coordination, and community participation.

Flood diversion redirects part or all of an excessive flow away from a vulnerable river reach, settlement, or agricultural area. Water may be conveyed through diversion channels, floodways, canals, tunnels, spillways, or natural depressions and discharged into another river, reservoir, wetland, or safe storage area. A diversion scheme must have sufficient capacity and a dependable control structure while avoiding unacceptable flooding, erosion, sediment deposition, or environmental damage elsewhere. This chapter explains the purpose, principles, and methods of flood diversion. It covers site selection, diversion routes, hydraulic and structural components, design discharge, operational requirements, advantages, limitations, maintenance needs, and the role of diversions within integrated basin-level flood-control planning.

Flood estimation determines the probable magnitude and frequency of flood events for designing hydraulic structures and managing flood risk. Intense rainfall over a catchment generates excess water after interception, infiltration, evaporation, and depression storage have been satisfied. This runoff reaches the drainage system and may cause flooding when channel capacity is inadequate. Reliable estimates help engineers select suitable dimensions for dams, spillways, bridges, culverts, reservoirs, and other protective works. This chapter describes rainfall-based and streamflow-based estimation techniques, including the Rational and Cook’s methods, unit-hydrograph procedures, frequency distributions, Gumbel, log-normal and Log-Pearson Type III analyses, empirical formulae, flow-mass curves, and partial-duration series.

Hydrology examines the occurrence, circulation, distribution, and properties of water in the atmosphere and on Earth. Solar energy drives the hydrologic cycle through evaporation, condensation, precipitation, infiltration, runoff, and groundwater movement. Rainfall first satisfies interception, depression storage, evaporation, and infiltration before excess water begins flowing across the surface and into channels. When runoff entering a river exceeds its conveyance capacity, flooding may occur. This chapter explains clouds, precipitation measurement, rain-gauge networks, rainfall consistency, infiltration, runoff mechanisms, hydrographs, unit hydrographs, empirical runoff models, and stage-discharge relationships. These concepts provide the scientific foundation required for analysing floods and designing appropriate control measures.

Flood management is a continuing process of assessing flood risk and coordinating prevention, preparedness, response, recovery, and adaptation. Unlike flood control, which often emphasizes physical structures, integrated flood management accepts that floods cannot always be eliminated and seeks to balance their risks and beneficial functions. It protects life and property while considering river-basin development, environmental sustainability, social needs, and economic feasibility. This chapter explains flood-management concepts, objectives, purposes, and techniques. It discusses structural and non-structural actions, forecasting, watershed treatment, afforestation, rainwater harvesting, floodplain zoning, community preparedness, institutional responsibilities, interlinking proposals, and government programmes. Emphasis is placed on coordinated, basin-wide and risk-informed decision-making.

Flood routing predicts how a flood hydrograph changes as it passes through a river reach or reservoir. Storage, channel geometry, friction, inflow distribution, and outlet conditions generally reduce, delay, or otherwise modify the flood peak. Routing results help forecast downstream water levels, determine reservoir releases, design spillways and channels, issue warnings, and evaluate flood-control alternatives. This chapter introduces the continuity and storage principles underlying flood routing and distinguishes reservoir routing from channel routing. It discusses hydrologic and hydraulic approaches, including level-pool, Muskingum, and related techniques. Attention is also given to inflow and outflow hydrographs, routing coefficients, travel time, attenuation, data requirements, assumptions, calculations, and practical engineering applications.

9.1 Introduction

Flood water which is in the form of a hydrograph when passes down a river section undergoes several changes in its form. There may be some addition of water to the river section when the flood wave passes down the river section. There may be some diversion of water from the section. Thus, depending on the addition or abstraction of water to the incoming flood water, shape of the flood hydrograph in the downstream section may change. Sometimes channel storage and resistance to flow of water in the channel section also affects the shape of the flood hydrograph.

A flood occurs when water exceeds the carrying capacity of a river, stream, drain, gully, or another natural or artificial channel and spreads over adjoining land. Its severity depends on water volume, depth, velocity, duration, timing, and the vulnerability of affected communities. Prolonged inundation can severely damage crops, property, infrastructure, water supplies, and human and animal life. Night-time floods may be particularly dangerous because warnings and evacuation become difficult. This chapter introduces flood occurrence and mechanisms, India’s and the world’s flood history, flood-prone regions, flood types and causes, major consequences, and the responsibilities of Indian flood-control and forecasting agencies.

7.1 Introduction

Flood is an unusually high stage in a river resulted due to high rainfall or snow melt which causes large flow of runoff in it. During flood, the river overflows the banks and inundates the adjoining areas. Flood causes heavy damages to buildings and hydraulic structures besides causing catastrophic loss to human life and property. It causes great economic loss due to disruption of many structures and damage to agricultural fields. Many forest and aquatic lives are affected by the flood. Hundreds of crores of rupees are spent every year to control, forecast and manage the flood.

12.1 Meaning and Definition

A flow chart is a graphical or symbolic representation of a process. Each step in the process is represented by a different symbol and contains a short description of the process step. The flow chart symbols are linked together with arrows showing the process flow direction. This diagrammatic representation can give a step-by-step solution to a given problem. Flowcharts are used in analyzing, designing, documenting or managing a process or program in various fields.

6.1. Determination of Hydraulic Conductivity of Saturated Soil: Laboratory Methods

Hydraulic conductivity of a saturated soil indicates the ease with which water is transmitted through the soil pores. If a constant water head (h) is maintained on a saturated soil column of length (L) and the volume of water (V) percolating per unit time (t) through per unit cross sectional area (A) to the other end, then according to Darcy’s Law the rate of flow of liquid or flux (q) is proportional to the hydraulic gradient (ΔH/L) across the length of soil column.

7.1 Determination of Hydraulic Conductivity of Saturated Soil Laboratory Methods

Hydraulic conductivity of a saturated soil indicates the ease with which water is transmitted through the soil pores. If a constant water head (h) is maintained on a saturated soil column of length (L) and the volume of water (V) percolating per unit time (t) through per unit cross sectional area (A) to the other end, then according to Darcy’s Law, the rate of flow of liquid or flux (q) is proportional to the hydraulic gradient (ÄH/L) across the length of soil column.

Floriculture is the most important aspect of urban agriculture, which fulfils the need for beautification, recreation, entertainment and income earning. In broader sense, it includes growing flowering and ornamental plants in gardens, rooftops and terraces. Floriculture comprises of house plants, flowering plants, pot plants, cut flowers and decorative foliage. It also deals with cultivation of cacti, orchids, succulents, bonsai, ferns and plants grown in landscape gardening.

Role of flowers in our life

• It is a unique gift of nature to relax human mind
• The fragrance and beauty of flowers bring joy and happiness
• Flowers are used as a symbol of grace and sophistication
• Flowers are used in religious rituals for offering during worship

1.1. Floral biology

1.1. 1. Types of inflorescence

Group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches.

Technical Term           Definition

Fluid Mechanics         Fluid Mechanics is a study of physical behavior of fluids and fluid systems, and laws governing their behavior. It incorporates action of forces

                                   on fluids and the resulting flow pattern

Fluorescein diacetate (3’ 6’-diacetyl-fluorescein) is a fluorescein conjugated to two acetate radicals. This colourless compound is hydrolysed by both free (exoenzymes) and membrane bound enzymes, releasing a coloured end product, fluorescein. This end product absorbs strongly in the visible wavelength (490 nm) and can be measured by spectrophotometry. The enzymes responsible for FDA hydrolysis are plentiful in the soil environment. Non-specific esterases, proteases and lipases, have been shown to hydrolyse FDA. The hydrolysis of FDA by soil enzymes can be estimated by methods of Adam and Duncan (2001).

Abstract

The anomalies observed in the reverine systems have been demonstrated to be the potential tool in deciphering the tectonically active zones. Such various drainage anomalies viz: radial drainages, anomalous compressed meanders, eyed drainage and the youthful floodplains observed in Annamali – Palani - Varushanad hill ranges of the Western Ghats of Tamil Nadu show that the N-S and NE-SW trending faults are tectonically active in the recent years.

Introduction
 
Arid western part of Rajasthan which contains the Indian segment of the Thar Desert, accounts for ~62% of the country’s hot arid area and is a region of low rainfall. Under such physico-climatic situation, fluvial processes function much less frequently and more episodically than the aeolian processes, but their impacts on landforms and society are large, as noticed on several occasions in arid regions. There is a distinct east-west gradient of rainfall and temperature in the region. Along the eastern margin bordering Aravallies, the mean annual rainfall is 500 mm while in the westernmost part at Jaisalmer, it is less than 150 mm. The rainfall is largely monsoon driven which brings 80 - 90 per cent of total rainfall received during the year. There is large inter-annual rainfall variability of rainfall which leads to climatic extremes of drought and floods of different magnitudes. For example on an average, the Thar Desert in India experiences flood-causing rainfall in 2-3 years in a decade, but a maximum of 5 flood causing rainfall years in a decade was recorded during the 1950s, 1970s and the 1990s (Rao et al. 2006).

SUMMARY

Fly ash, a waste product generated by coal based thermal power plants. The annual production of fly ash in the country has increased from 40 million tones in 1994 to 110 million tones in 2004 and it is expected that by 2012 the annual production of fly would reach the mark of 170 million tones. Owing to its physico-chemical characteristics, it has a vast potential for use in agriculture, forestry and wasteland reclamation. Application of fly ash into soil has been reported to increase the water holding capacity, hydraulic conductivity, porosity and decrease bulk density, modulus of rupture and surface encrustation. The studies conducted by various organizations on fly ash use in different crops have revealed significant increase in the crop yields such as wheat, maize, paddy, soybean, sunflower and vegetables like brinjal, tomato, potato, cabbage. Application of fly ash has been found to increase the level of heavy metals  viz., Co, Pb, Mo, As and Se as well as the activity of radio-nuclides i.e., ⁴⁰K, ²²⁶Ra, ²²⁸Ac  in the soil- plant system; however, the levels of all these heavy metals and radio-nuclides were found to be well below the permissible limits.

Cowpea is a quick growing leguminous forage crop. It is usually grown mixed with cereal fodders and grasses to improve the nutritive value of the herbage. It contains 20 – 24 % crude protein, 43 - 49 % neutral detergent fibre, 34 – 37 % acid detergent fibre, 23– 25 % cellulose and 5 – 6 % hemicelluloses on dry matter basis. The digestibility of cowpea fodder is above 70%. Cowpea can be grown under partial shaded conditions. It is an excellent cover crop, which suppresses weeds and enriches the soil. Cowpea requires warm climate with good atmospheric humidity. It can be grown in kharif as well as in zaid season.