MODELING AND MANAGEMENT OF FLOOD FLOWS

Abstract

In most developing countries of the tropics tremendous growth in population has been recorded during the last four to five decades. This has resulted into increased water demand in the domestic, agricultural, commercial and industrial sectors. With limited water available during the four monsoon months, it has become necessary that each unit of water be either judiciously consumed or else be stored. In majority cases, this water demand is met through the ground water supplies. Consequently, lowering of ground water table has become a common phenomenon which is observed throughout. Suitable plans need be drawn for natural recharge of groundwater table by storing the excess flood waters in the surface depressions which may not be economically viable. Also, there is a need to explore where ever possible, the river bed itself be utilized for providing a safe passage to floods as well as to utilize it for sto#age of water for recharging the aquifers. With these objectives in view this dissertation has been worked out. The objectives of the study have been defined along with the introductory remarks (Chapter 1). The literature survey relevant the problem pertaining to the hydrologic design and models to be adopted has been reported in Chapter 2 of the thesis. Since most of the catchments of rivers in developing countries happen to be ungauged, therefore, a hydrologic model utilizing the properties of the Rational Formula and the Manning's equation has been developed. This is resulted into the development of a nomograph involving the runoff coefficient, rainfall excess intensity, discharge per unit catchment area per unit channel width, Manning's roughness, runoff depth in channel, velocity of flow in channel, Froude's number and the time of concentration. The proposed concepts have been discussed in detail in Chapter 3. A case study has been reported in Chapter 4. A Catchment area of 3200 km2 has been considered. Flood produced is allowed to pass through a constricted section of the .river. The levees on the two banks have been strengthen to form the dykes. The flood in excess of safe discharge has been diverted through the broad crested weir sections to fill the depression on the two sides of the river. The proposed management plan saves the two economic sectors located in the downstream. The, diverted water in the depressions will infiltrate, percolate and will ultimately recharge the aquifers.