When the rate of rainfall or snow melt water influx exceeds the absorptive capacity of the soil, the excess water flows over the surface as overland flow. In general, the intensity of rain increase, the rate of infiltration increases. Some of the water percolate or seep down to an impervious layer of clay or rock to be stored as ground water. In ground water zone, percolation happened which is caused by gravity and capillary forces, the water find its way into streams or springs, and eventually rivers and
The design must also consider the stormwater reaching in the lower critical level areas through natural stream flow on manmade ditches. In Surat city some critical location flooding occurs during monsoon season. It is that interval of time in which river Tapi flows under high flood condition also. According to location there are some types of flood occurs in city
Swelling potential increases with the increasing amount of clay minerals. Soil Water Chemistry Swelling is repressed by increased cation concentration and increased cation valance. For example, Mg+2 cations in the soil water would result in less swelling than Na+ cations. Soil Structure and Fabric Flocculated clays tend to be more expansive than dispersed clays. Cemented particles reduce swell.
STORMWATER MANAGEMENT Defining the Problem Stormwater runoff can be defined as “…the water that flows over the land from rainfall during or after a storm event or as a result of snowmelt” (Pyzorha 1994). Generally, part of this runoff will be absorbed through infiltration, while the rest will make its way to streams and lakes. As watersheds experience an increase in urbanization, however, impervious coverage increases, thereby reducing infiltration. Reduced infiltration increases the possibility and intensity of flooding (Booth and Jackson 1997), as well as the likelihood that runoff will become contaminated with pollutants, thereby threatening aquatic ecosystems. The relationship between watershed urbanization and aquatic ecosystem conditions
: from rain fed cultivated area to irrigated one. Land use and land cover changes have environmental consequences, one of which is, these changes mostly dictates the volume and speed of runoff from precipitation and govern soil erosion rate. Wijitkosum (2012) states the factor that significantly affects the soil displacement by rain is the state of land cover or vegetation
Based on the analysed documents, reports and media articles flood in Windhoek is not common even though it has occurred and has caused major damage especially to the roads in the city. The City of Windhoek’s division for Disaster management is responsible for the management of disasters such as floods, however the division doesn’t have documents that indicate how the division intend on addressing a major flood should it occur therefore, a thorough inspection of its Disaster management plan was done and is discussed. According to the auditor general report on emergency preparedness of the prime minister, there are six components of disaster preparedness in Namibia these includes, Institutional Framework of the city, Early Warning Systems identified, Information and Communication Systems, Resource Bases, Response Mechanisms and Public Education and Training offered. These are the basis to which the preparedness of the city of Windhoek is assessed including the policies and other institutions that may contribute to the management of floods in the City. 2.
1.2 Statement of the Problem As cited in Exnner and Spadling, 1993, Groundwater pollution with nitrate is a global problem in many parts of the world; groundwater is the source of drinking, agricultural, industrial and domestic uses. In Ethiopia the degree of pollution is generally not large except the surface waters of Addis Ababa and groundwater of Dire Dawa city. Nitrate is one of the major contaminants in urban area in different parts of the world including agricultural areas where fertilizers are being extensively used. The possible sources for the enrichment of nitrate in both cities could likely be waste disposal in the urbanized areas and agricultural activities in rural areas and also the combined effects in some others. The nitrate
Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other. When liquefaction occurs, the strength of the soil decreases and, the ability of a soil deposit to support foundations for buildings and bridges are reduced. Liquefied soil also exerts higher pressure on retaining walls, which can cause them to tilt or slide. This movement can cause settlement of the retained soil and destruction of structures on the ground surface.
Pinatubo, especially in river valleys. It caused the devastation of low-lying areas and destruction of structures along its path. To protect the residential areas and farmlands during heavy rainfall, River embankments also known as mega-dikes were constructed.
The substances it carried are deposited in another part or completely removed from the material through percolation when there is evaporation of soil moisture at the surface influencing an upward movement of water (Nyman et al., 1993).Precipitation therefore brings about redistribution of substances in soil body which can either be in soluble form or in suspension (Troeh and Thompson (2005). Temperature This is another agent of climate which influences the process of soil formation by influencing the rate of biological and chemical reactions occurring in the soil. According to Bronick and Lal (2005), High temperature increases the rate of chemical weathering, thereby resulting to high rate of soil formation and it also favours the activities of microorganisms in the soil. Soil formation through chemical weathering in areas of low temperature is minimal because, low temperature slows down the process of decomposition (Six et al., 2000). Biological