Hydrological engineering, sometimes called hydrologic engineering or water resources engineering, is an engineering specialty that focuses on water resources. Hydrology is that the study of the movement, distribution, and quality of water on Earth and other planets, as well as the hydrologic cycle, water resources and environmental watershed sustainability. Hydrological engineering is chiefly concerned with the flow and storage of water, principally water and sewage. It is the study of the properties, distribution, and circulation of water on the surface of the land, in the soil and underlying rocks, and in the atmosphere Topics commonly covered include urban drainage, water supply, wastewater treatment, river management and coastal protection. Hydrological engineering also focuses on preventing floods and lessening the effects of floods, droughts and other natural disasters. Means, Hydraulic and Hydrologic engineers work to prevent the supply water for cities, industry and irrigation, to treat wastewater, to protect beaches, and to manage and redirect rivers. Hydraulic engineering is the application of fluid mechanics principles to problems dealing with the collection, storage, control, transport, regulation, measurement, and use of water. Related branches of Hydrologic Engineering include hydrology and rheology while related applications include hydraulic modeling, flood mapping, catchment flood management plans, shoreline management plans, estuarine strategies, coastal protection, and flood alleviation. Common topics of design for hydraulic engineers include hydraulic structures such as dams, levees, water distribution networks, water collection networks, sewage collection networks, storm water management, sediment transport, and various other topics related to transportation engineering and geotechnical engineering. Equations developed from the principles of fluid dynamics and fluid mechanics are widely utilized by other engineering disciplines such as mechanical, aeronautical and even traffic engineers.