Soil Thematic Geo Data base for Dubai Emirate using Remote Sensing & GIS Hussein Harahsheh Global Scan Technollogies, Dubai P.O.Box: 1286, UAE Tel: +971-4-2699895, Fax: +971-4-2699307 husseinh@belhasa.ae Mohamed Elias Global Scan Technollogies, Dubai P.O.Box: 1286, UAE Tel: +971-4-2699895, Fax: +971-4-2699307 AbdulAzim Elniweiri Dubai Municipality P.O.Box 67, Dubai,UAE Mohamed Mashroum Dubai Municipality P.O.Box 67, Dubai,UAE Yousef Marzouqi Dubai Municipality P.O.Box 67, Dubai,UAE Eman Al Khatib Dubai Municipality P.O.Box 67, Dubai,UAE B.R.M. Rao National Remote Sensing Agency (Dept. of Space, Govt. of India) Balanagar, Hyderabad - 500 037, India ABSTRACT The soils of Dubai were mapped using remote sensing satellite data (IRS- P6 LISS IV ) at 1: 25,000 scale . The soils of the study area were classified up to series level and their associations as per the Keys to Soil Taxonomy (Soil survey staff, 2003). In Dubai area 26 soil series have been identified and 13 soil series were identified in Hatta area. The soils of Dubai area are generally coarse textured, sandy, highly calcareous and undeveloped. Soils in the coastal area, low-lying areas and depressions are highly saline. The soils of the inland areas are either saline or sodic. The Hatta area is characterized by mountains with steep side slopes, which are devoid of vegetation. Almost all the hills are barren ( 80-90%) and rocky without any soil cover. The soil in the hills are shallow to very shallow, skeletal in nature, and highly calcareous The soil have been evaluated for land capability classes and it was found that 17 % of the total study area was under land capability class IV, with the major limitations of climate and soil. These soils are suitable for marginal agriculture only with the support of assured irrigation. The dominant land capability class identified in Dubai is class VI which occurs in 65% of study area. The dominant land capability class in Hatta is Class VIII and accounts for 85.3 % of the study area. Thus, the soil have major limitations of climate and soil which can be improved by adopting various soil conservation measures like sand dune stabilization, shelter belts, afforestation etc. INTRODUCTION The socio-economic development of any country is based on land resources and water resources. Due to increase in population, these resources are over stretched often leading to resource depletion There is evidence to show that a majority of world over land resources is under pressure and is undergoing degradation at an unacceptable rate (Kharin et al 1999, Harahsheh 2001) A recent research study on Middle East desertification shows the gravity of land degradation problems in all levels. It concluded that all Middle East is subject to degradation, mainly by vegetation degradation process, where 40% of study area is severely and very severely affected by vegetation degradation, followed by soil degradation process (27% severe and very severe wind erosion). Without doubt these results show the gravity of land degradation problem in the study area (Harahsheh, 2001). There is therefore need to prudently manage these delicate resources. The situation in Dubai Emirates is no different. Moreover, Dubai being located in an arid desert belt, it is highly sensitive to a number of critical environmental issues. Soil is one such important issue, as it is a non-renewable natural resource. Soil is in-fact at the heart of terrestrial ecology and is vital to our existence. Information on soils with regard to their nature, extent and spatial distribution along with their potential and limitations is required for a variety of uses, namely agricultural development, engineering, sanitary, recreation, aesthetic, etc. In addition, such information is also required for modeling and environmental impact analysis. Therefore, it is imperative that we manage and conserve soils judiciously to meet the growing need for food, fodder, fiber and fuel. For this purpose, we must have an in-depth knowledge about different soils, their morphology, characterization, behavior, kind and degree of problem and their extent and distribution on the landscape. Soil surveys can be carried out using the modern technology of space borne remote sensing. In-fact this technique has proved to be a powerful tool, because it enables to study resources in spatial domain in time and cost effective manner. Survey of literature reveals that satellite data of LANDSAT MSS / TM, SPOT, IRS LISS I, II, III, IV and PAN and IKONOS etc. were used to map soils at different scales from 1: 250000 to 1: 12500 scales. Dubai municipality has taken the initiative to use the remote sensing technology for thematic mapping of Dubai Emirates area using Satellite Imagery including soil mapping. Integration of thematic maps, soil and others are used for better and optimal utilization of various land and water resources and can be used for many applications like demarcation of potential ground water zone and for site selection processes etc. Global Scan Technologies (GST) in association with National Remote Sensing Agency (NRSA), Dept. of Space, Govt. of India, has executed has replied to Dubai Municipality initiative and produce a set of thematic mapping information including soil map of Dubai Emirate as it is described hereafter. REMOTE SENSING APPLICATION IN SOIL RESOURCES STUDY Remote sensing technique helps in speeding up soil mapping; produce better quality soil maps and improve our understanding of the interaction of soil, weather and crop growth. However, remote sensing is a tool to be used to identify and map soils and to monitor their degradation; it is not a substitute for field data collection (Evans R.,1990). Most remote sensing techniques use radiation, which shows only a shallow penetration upon interaction with soil, rock and plants. By using these techniques it is only possible to obtain direct information about the surface of the soil or vegetation covering the soil. Even remote sensing aids that have deeper penetration (microwaves) or provide data (with thermal waves) which are the result of soil physical structure that is not limited to the soil surface alone. Therefore it would be a mistake to regard interpretation of such remote sensing data as decisive for soil distribution without the undertaking of fieldwork (Mulders M.A., 1987). Until the late 1920s, soil surveys had been carried out through conventional approach, which is tedious, time-consuming, cost-prohibitive and impractical in inhospitable terrain. Remote sensing has augmented the efficiency of soil survey programmes, by providing synoptic coverage of the Earth’s surface at regular intervals. During the period from eighties to mid nineties, the second generation of remote sensing satellites viz., Landsat-TM, SPOT and IRS satellites were launched with higher spatial and spectral resolutions which had enabled to map soils at 1:50,000 scale at the level of association of soil series. The information on soil resources was generated by understanding of the spectral response pattern of soils (Westin and Frazee,1976; Dwivedi , 1985) . many studies have been conducted using SPOT (Agbu,1991; NRSA 1993); and Indian Remote Sensing Satellite ( IRS) (Rao et al 1998; Rao et al 2001). Base on that many national soil mapping projects were prepared using these technologies ( ( NRSA 1995, NRSA 1996, NRSA 2000, NRSA 2001, NRSA 2002). OBJECTIVE The objective of this study is to generate thematic geodatabase information on soil resources of Dubai Emirate. The soil map of Dubai and Hatta was prepared at 1: 25,000 scale using the Indian Remote sensing Satellite (IRS-ID) Linear Imaging Self Scanning Sensor (LISS IV) data. The soils of the study area were classified as per USDA (2003) up to soil series and their association level. STUDY AREA The project area covers the Dubai Emirate (UAE) an area of 4000 sq km (Figure1).  Figure-1: Study Area The overall climate of the Emirates is subtropical, warm and arid. Air temperatures range between 350 to 500 C from May to October during the middle of the day and between 200 to 350 at mid-day during the winter months. The average annual rainfall of the Emirate which falls mostly during winter months is about 100 mm. The rainfall, however, is very erratic and varies extremely both from year to year and place to place. Some moisture also condenses in the form of fog and dew, especially in the coastal belts. Strong winds and sand storms area also of common occurrence throughout the Emirate. They are especially more frequent and severe during summer months. Sand dunes are the dominant feature of the landscape over most of the Emirate. INPUT DATA In the present study for generating base line information on soil resources of Dubai and Hatta area the Indian Remote sensing Satellite (IRS-ID) Linear Imaging Self Scanning Sensor (LISS-III & LISS IV) data have been used. Ortho-rectified IKONOS data is provided by Dubai Municipality for Geo-referencing of IRS - P6, LISS IV data Besides the satellite data the base maps prepared by the project team, Published soil maps, topographic maps, climatic data etc. are also collected and used as collateral data. METHODOLOGY Essentially soil survey is a study and mapping of soils in the field. It is the systematic examination, description, classification and mapping of soils of an area and it comprises of a group of interlinked operations involving
 Figure 2: Methodology for mapping soils PRELIMINARY VISUAL INTERPRETATION The steps involved in pre-field interpretation is monoscopic visual interpretation of Indian Remote Sensing Satellite (IRS) ID LISS-III and IRS P6 LISS IV data at 1: 25,000 scale based on the standard remote sensing techniques using image characteristics such as tone, texture, pattern, shape, size, association etc. in conjunction with the collateral information available in the form of published maps and reports. A tentative interpretation key in terms of lithology, physiography, land use/ land cover, erosion /salinity / alkalinity hazards and image elements was developed. Field work A field visit was undertaken in Dubai and Hatta study areas, to study important characteristics of soils and associated land features for mapping soils. The first step in soil survey begins with general fact finding exercise through a reconnaissance of the area, so a preliminary study on the landform, geology, climate and vegetation of the study area was undertaken. For carrying out the fieldwork the scientists traversed the study area with a base map, satellite imagery for the first three days. During the traverse the scientists noted the variations in landforms and associated soils. The ground features were also correlated with the image features. Soil profile studies and sample collection The detailed soil-site study was undertaken in each soil-mapping unit by general traversing and by collecting surface soil, minipit and soil profile observations at intervals depending on soil variability. The soil profiles /pedons (A vertical cut from the surface down to the hard rock from which the soil is formed gives the soil profile and in the profile several successive characteristic layers can be identified. A profile pit with exposed vertical face of approximately 1 meter across to an appropriate depth (nearly 1 m) was satisfactory for most soils. Each layers (horizons) was studied for various morphological features such as colour, texture, structure, consistency etc. The frequent profile sampling enabled to determine the depth of various horizons and also the horizons of gains (alluvial) and losses (eluvial). Sometimes, by merely looking at the surface soil and at other times, by rubbing the surface soil between thumb and fingers (to determine soil texture) reflects soil properties. A detailed description of each profile was noted down on the pro-forma. The proforma includes many parameters, which were collected. This includes, Location of the soil profile in terms of latitude and longitude, Physiographic unit, Parent material / Geology, Slope (%),Soil characteristics, Soil depth, Soil texture, Consistency and much more. Also Effervescence test was Performed by squirting 10% HCl on the soil to determine the free carbonates. In Dubai and Hatta area 129 soil profiles were excavated and large number of observations were also taken. In total 333 soil samples were collected. LABORATORY ANALYSIS Physical & Chemical Properties: Particle Size Analysis – was carried out by the international pipette method (Piper, 1966) using Sodium Hexametaphosphate as a dispersing agent. The textural class was determined using the USDA textural triangle. Chemical analysis including, Soil Reaction (pH), Electrical conductivity (EC), Organic Carbon (OC), Calcium Carbonate (CaCO3) and Cation Exchange Capacity (CEC). POST FIELD INTERPRETATION Preliminary interpreted soil boundaries from IRS-P6 were modified using field information and final thematic details were transferred on to the base map. Finally the soils were classified in the light of soil morphology features, soil physical and chemical properties as described in soil survey procedure (USDA, 2003). Thus, the landscape map was converted into soil escape map in terms of soil series and / associations thereof. Based on the variations in the soil and site characteristics 26 soil series have been identified in Dubai area and 13 series in Hatta area. DESCRIPTION OF SOILS OF DUBAI The soils are generally coarse, sandy, highly calcareous and undeveloped. They are deficient in organic matter. Soils in the coastal belt and low-lying areas and depressions are highly saline and where as the soils in the interior of the desert are either saline or sodic. The major Landscapes identified in the study area are coastal plain, lower aeolian plain and upper aeolian plain. These major landscape units were further subdivided into different physiographic units such as Beach, tidal flats/ mudflats, salt flats ( young and old) and dunes over the coastal plain The lower aelion plain has low sand dunes, longitudinal dunes, interdunal flat areas ( sandy , saline & sodic ) ,dunal complex areas and residual hills and linear ridge. The upper aelion plain has dunal complex, interdunal flats (Sandy and sodic) low sand dunes. The soil map of Dubai is shown in Figure 3. and table 2 describe the soil series in Dubai. In Hatta area the major Physiography units identified are structural valley region, piedmont area, residual hills, denudational hills ( Periodite/ dunite/ gabbro),denudational hills ( limestone /dolomite/marble) and structural hills (periodite/ dunite / gabbrointerbedded), The soil temperature regime of Dubai and Hatta is Hyperthermic, which can be inferred from the climatic data of Dubai (Table 1). The soil moisture regime is aridic / Torric. In general all the soils of Dubai are calcareous. As the study area falls under arid region the soils occurring in these areas will normolly have an aridic (torric) moisture regime. On analysis of all the soil samples collected during the ground truth, it can be inferred that all the soils of Dubai and Hatta area are calcareous. The other features of the soils occurring in the study area are discussed separately.     LAND CAPABILITY Soil resources maps, as mentioned earlier, provide information on location, spatial extent and physico- chemical characteristics of soils. Land capability classification is an interpretive grouping of soils mainly based on 1) the inherent soil characteristics ii) external land features and iii) environmental factors that limit the uses of land. Scientific soil surveys provide information on the first two aspects. Effective soil depth, soil texture, permeability of sub soil and sub-stratum, available moisture capacity, reaction, inherent fertility, organic matter content, salinity and/ sodicity are some of the important inherent soil characteristics. Amongst important land features are natural surface drainage, slope, erosion, wetness, and gravelliness. Besides, the aforesaid factors, climate does play a very significant role in deciding the potential of a given piece of land for sustainable development. In the land capability classification there are eight classes. Classes I, II and III include the land suited for regular cultivation. Class IV land is fairly good for cultivation but it’s safe use for cropping is very limited by natural features such as slope, erosion, unfavourable soil characteristics and adverse climate. Classes V, VI, VII are not suited for any cultivation but may be used for grazing or forestry, according to adaptability. Class VIII land is suited only for wildlife or recreation. Tabel2. REFERENCES
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