In this Geoshortqa we are going to know about types of Sand Dunes. Types of Sand Dunes, Geoshortqa Sand Dunes Sand dunes are heaps of sand found in deserts . Generally , their heights vary from a few metres to 20m , but in some cases dunes are several hundred metres high and 5 to 8 km long . The formation of sand dunes requires • Wind of high velocity • Abundant sand • Obstacles such as trees , bushes , forests , rock outcrops , walls against , which dunes may settle • Ideal places i.e. dune complex , dune colony or dune chain . Dunes formed due to obstacles like hushes , walls etc. are called nebkhas , where dune formed besides desert depressions are called lunettes. Dunes are classified on the basis of morphology , structure , orientation , location , internal structure , ground pattern and number of slip faces . These are the various types of sand dunes a) Transverse Dunes are dunes deposited transverse to the prevailing winds direct...
| In this Geoshortqa we know about Models of Urban Land Use Models of Urban Land Use A number of theories have been devised to describe and explain the patterns involved in the geographical arrangement of various categories of urban land use in different cities. The three popular models, based on empirical studies in different cultural and economic settings, which explain the internal structure of cities are as follows (i) The Concentric Zone Model by E W Burgess. (ii) The Wedge or Sectoral Model by Homer Hoyt and M R Davis. (iii) The Multiple Nuclei Model by C D Harris and EL Ullman.  |
| Models of Urban Land Use, Geoshortqa |
Concentric Zone Model
The Concentric Zone Model of urban land use or 'ecological theory of city structure' was proposed by E W Burgess in 1924 and then revised in 1927.
A system of five concentric zones was identified by Burgess, each characterised by a particular type of land use.
(i) Zone I (Central Business District-CBD) : The central place in a city is occupied by CBD. It is the most readily accessible part of the city. It is the focus of city's commercial, social and civic life. The land value and rent of space are very high in the CBD.
(ii) Zone II (Zone in Transition) : This zone surrounds CBD. It is the zone of residential deterioration due to invasion of business enterprises. Some slums also develop in this area. This area is occupied by lower income groups who live close to the place of work as they cannot afford high cost of transport.
(i) Central Business District (CBD)
(ii) Zone in Transition
(iii) Zone of Independent Workmen's Home
(iv) Zone of Better Residence
(v) Commuter's Zone
(iii) Zone III (Zone of Independent Workmen's Home) : This zone mainly consists of homes of factory workers and labourers. Usually, these are the people who have moved out of zone II. The density and occupancy of this zone is always high.
(iv) Zone IV (Zone of Better Residence) : This zone is mainly occupied by middle and upper middle class people. It includes small businessman, professional people, better paid government employees and salesman. This area is dominated by single families.
(v) Zone V (Commuter's Zone) : This zone is occupied by people who commute to city for their work. It is characterised by dormitory towns and large spacious houses having their own lawns. The cost of land is comparatively low.
Wedge or Sectoral Model
The Wedge or sectoral model of urban land use was propounded by Homer Hoyt and MR Davis in 1939.
This theory asserts that the patterns of urban land use are setup by the arrangement of routes radiating out from city centre which create a sectoral pattern of land and values of rent which in turn influences urban land use pattern.
1. CBD
2. Wholesale and light manufacturing
3. Low class residential
4. Medium class residential
5. High class residential
This model takes into account both the distance and direction of expansion and acknowledges the importance of transport routes on the growth of the city.
Thus, a high-rent residential district in one sector of the city will migrate outwards by the addition of houses along its outer arc. On the other hand, low rent housing expands outwards in a different direction.
Multiple Nuclei Model
The Multiple Nuclei Model of Urban Structure was propounded by Harris and Ullman in 1945.
The proponents of this model advocated that land use patterns in most large cities develop around a number of discrete centres of nuclei rather than a single centre. This clustering of related land uses around these nuclei in the city creates a cellular structure. The term 'nucleus' has been defined as an attracting element around which urban growth may take place.
According to this model CBD loses its uniqueness with the growth of city. Centres serving high income areas are characterised by high grade activities, which results in proliferation of dominant nuclei and development of other centres on a regional or specialised basis, thus strengthening multiple nuclei generalisation.
1. CBD
2. Wholesale and light manufacturing
3. Low class residential
4. Medium class residential
5. High class residential
6. Heavy manufacturing
7. Outlying business district
8. Residential suburb
9. Industrial suburb
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