Abstract
Digital elevation models (DEMs) are created to study the topography of the area by using point krigging method of gridding. The results show a significant level difference between the start and end points of the valley sloping naturally. A longitudinal profile shows an average slope of 2.6% in a stretch of 15 km inside the area under study. Later, the detailed watershed and runoff analysis have been performed by preparing various maps using IDF curves available for the area. The area is found to experience sufficient rainfall for a 50 to 100-year storm return period. The expected location and amount of runoff water accumulation have also been determined which may help for the construction of water storage or rainwater harvesting facilities. The chapter shows the role of GIS-based techniques for the hydrological analysis of difficult terrains which can be applied for planning and management of water storage facilities in underdeveloped areas.
TopBackground
Very less literature has been found on the topic of gravity hills alone yet to talk about its hydrologic study. Most of the literature which is available discuss about the topographical aspects of such places and no hydrological study has been found specifically for a gravity hill. Regarding the topographical study of a gravity hill, Proffitt et al. (2001) did a lot of experiments on the perception of slants of hills. Their experiments concluded that the slant perceptions are always grossly overestimated. Bressan et al. (2003) have directly worked on the gravity hill phenomena by recreating the models of various gravity hill spots. They concluded that the gradient of the roads is misperceived due to the absence of a reference line or horizon and also that this phenomena is easy to be recreated artificially without putting any external force of magnetism or antigravity. Stefanucci et al. (2005) has discussed about the appearance of distance on sloping areas and more precisely on the hills. He concluded that the distances appear more on hills but his research is based on pedestrians walking uphill or downhill. Tsuinashi (2008) did an experimental work related with optical illusions by using pitched rooms and pitched floors. His experiments concluded that the vertical gradient of the roads or any surface in view could be misperceived and can work as an illusion. Kitaoka (2015) has discussed illusion on a gravity hill by using diagrams and included a case study of such spot in Radan, Serbia. Jaf (2009) has studied one such spot in Koya region, Kurdistan-Iraq. He performed visual inspections and took photographs to prove the phenomena of gravity hill existing within a small 200m section of road. Hengl et al. (2008) used around 2,000 data points to create the DEM of an area to study its hydrological and land cover properties by using maps. Mitra (2018) performed site suitability analysis to study the possible locations for rain water harvesting systems. She studied an area of West Bengal, India for the purpose. Jamil (2018) has done a detailed research on the topographical characteristics of Wadi Al Baida. He used various data resources to create digital elevation models to study the terrain of the area. Also, he provided logical reasoning to understand the phenomena of a gravity hill. However, no hydrological perspective was provided.
Key Terms in this Chapter
Runoff: Draining away of water from the surface of an area of land, a building or a structure, etc.
IDF Curve: Intensity-Duration-Frequency Curve, a graphical representation of the probability that a given average rainfall intensity will occur. It is given by a mathematical function that relates the rainfall intensity with its duration and frequency of occurrence. These curves are commonly used in hydrology for flood forecasting and civil engineering for urban drainage design.
Wadi: Arabic word for valley, a low area of land between hills or mountains, typically with a river or stream flowing through it.
Watershed vs. Catchment Basin: A watershed is simply the area of land that catches rain and snow and drains or seeps into a marsh, stream river, lake, or groundwater. Catchment basin is the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet.
Catchment Basin: An area of land where precipitation collects and drains off into a common outlet, such as into a river, bay, or other body of water.
Watershed: An area of land that feeds all the water running under it and draining off of it into a body of water.
Geospatial Data: The data or information that identifies the geographic location of features and boundaries on Earth, such as natural or constructed features, oceans, mountains, plains and more. Geospatial data is usually stored as coordinates and topology which can be mapped.