APPLICATION OF ADVANCED TECHNOLOGIES IN STRATEGING CONSERVATION OF WETLANDS AGAINST URBAN EXPANSION IN THE

COLOMBO DISTRICT, SRI LANKA

Plnr. Pushpa Gamage, Plnr. L H Indrasiri, and W R Navodani

Director (IS & GIS), Urban Development Authority, Sri Lanka; Tel: +112872390; e-mail: indrasiri@uda.lk

Deputy Director, (IM & GIS), Urban Development Authority, Sri Lanka; Tel: +112876297; e-mail: pushpa@uda.lk

GIS Officer, Urban Development Authority, Sri Lanka; Tel: +112875921; e-mail: novodaniwr@gmail.com

KEY WORDS: Wetlands, Urbanization, Spatial data, Geo-database, Zoning, and Regulations,

1.0 Introduction

Wetlands are critical component of our environment as it provides an important range of services in the context of environmental, social & economic sectors. Many wetlands are areas of great natural beauty and affect so much to the people. We recognized that most of the wetland ecosystems are indiscriminately exploited at present for residential, commercial and agricultural development, as well as providing space for dumping of industrial and urban refuse. In common opinion wetlands are “wastelands”, and thus reclaimable for economic benefits but its tangible and intangible benefits connected with social and environmental components are hidden and need to be stressed in local set-up. With the rapid urbanization and the urban sprawl to the city limits, wetlands are highly convenient to convert or to absorb urban activities.

The Ramsar Convention, to which Sri Lanka is one of the signatories since 1991, defines wetlands as; “areas of marsh, fen, peat land or water whether natural or temporary, with water that is static, flowing, fresh, brackish or salt, including areas of marine water, the depth of which at low tides does not exceed six metres”.

The broad definition makes sense to one realizes who that, to a certain degree, many areas are wetlands; some even say that the whole Sri Lanka with all its marshes, lagoons and paddy fields should be considered as wetlands!!!! However, most wetlands and thus the plants, animal and human communities that depend on these, are vulnerable in many ways;

1. Wetland ecosystems are dependent on water levels and inundation, that are easily modified by water usage, excessive or impede drainage, water regulatory works in upper catchments,

2. Wetlands depend on specific qualities of water that are easily affected by sedimentation, industrial affluent, garbage dumping, inflow of sewerage and other pollutants.

In this context this study is aiming to evaluate the growing concern over the rate of urbanization in highly urbanized part of the country against the potential capacities in conserving them in future.

2.0 Objectives

• Prioritizing conservation and protection of wetlands by extracting values from advanced technologies together with transforming diffusely spread data available in different format and maintained by number of agencies,

• Defining the appropriate uses of wetlands with proper identification by categorization of marginal lands for urban development,

• Developing preservation measures to be adopted by filling site specific data, • Proposing new areas to be added to existing legislations in areas to cover adequate

preservation measures of highly vulnerable wetlands. • Develop geo-spatial database and introduce wetland zoning with area/site specific

regulations.

3.0 Study Area

Colombo District has been selected as the study area as it is the most urbanized district among 25 districts in Sri Lanka having concentration of the main commercial hub and the administrative city within it. Colombo District comprises of 14 Local Authority areas having rapid changing pattern of urban expansion. There are 05 MCs’, 05 UCs’ and 04 PS areas in this district.

Location of the Colombo District Distribution Pattern of Wetlands

4.0 Methodology

Increasing human population and expanding physical development activities require more and more lands which is creating much pressure on wetlands. It is an illusion to expect all wetlands can be preserved. Although, the most important wetlands should be given Protected Area status, others will be claimed for development purposes, introducing proper drainage plans. Therefore it was very difficult task to find out marginal wetlands for this purpose. The methodology adopted for this study could facilitate to understand the location of those areas.

1st Step

Extract wetlands from Satellite images and available topo sheets for the years of 1963, 1993, 2001 and 2009. Data processing, extraction of information and analysis were performed using ERDAS (Earth Resources Digital Analysis System) Imagine (Version 9.0), ArcGIS 9.2 & 9.3, and Arc View (version 3.2a) software packages.

The following base data were taken for this study.

1. Topographic Maps at the scale of 1:63,360, vector data 2. Topographic Maps at the scale of 1:50,000, vector data 3. High Resolution IKONOS Satellite images, 2001, raster data 4. High Resolution IKONOS Satellite images, 2009, raster data

2nd Step

A comprehensive data base was developed at small scale (1:50,000) for the entire district and large scale (1:2,000) database was created to identify specific areas especially where urban expansion was occurred.

3rd Step

Identification of Marginal Wetlands by using value scale,

Identify importance of wetlands under three major categories by considering following factors:

1. Uses of the wetlands, (Direct Use Value) a. Plant Production (various agricultural & horticulture activities) b. Animal Production (some fisheries, some cattle) c. Water Storage or Supply Energy d. Tourism & Recreation (high potential for eco-tourism) e. Research/Education f. Waste Water Disposal (large dumping of waste and solid waste, home and

industrial waste) g. Land Development (increasing land fill operations)

2. Functions of Wetlands (Indirect Use Values)

a. Water Quantity Regulations (flood control) b. Habitat for Fish (significance for river species) c. Habitat for Wildlife (important no. birds use the wetlands)

3. Attributes of the Wetlands (Non-use values, preservation values)

a. Biological Diversity (high faunal richness for the Colombo region) b. Scenic/ Landscape Beauty (oasis of rest in the city) c. Historical or Cultural Value d. Uniqueness (rare birds and species)

Then express the benefits of particular wetlands in a value scales. Such scales have been developed by International Conservation organizations which was adjusted and simplified by the Wetlands Conservation Project in Sri Lanka to some extent adding national flavours. That scale was used to value importance of wetlands in terms of urban expansion in the Colombo district. For all benefits, values are expressed in terms of regional, national and international significance. The following scales are applied to find out marginal wetlands;

Level 5: Very High Importance, the wetland is highly significant for the specific benefit, at a national or international level;

Level 4: High Importance: the wetland is highly significant for the benefit at a regional level, and has some significance at the national level;

Level 3: Medium Importance or Importance Not known: the wetland is highly significant for the benefit at the local level and has some significance at the regional level, or available data on the characteristics of this wetland do not allow definite valuation;

Level 2: Low Importance: the wetland has moderate or low local significance for this benefit;

Level 1: Insignificance: the benefit is very insignificant or absent;

5.0 Analysis

A format was prepared accordingly to the 3rd step and Value Matrix was used to see what kind of actions are required for categorization of wetlands or identifying marginal lands for development.

Below indicated a Value Matrix used to decide above decisions;

Attributes/

Functions Uses

General Value Level

1

2

3

4

5

General Value Level

1

A

NO MEASURES REQUIRED

B

CONSERVATION OF THE WETLAND REQUIRED

2

3

C

MANAGEMENT OF THE USED RESOURCES REQUIRED

D

CONSERVATION URGENTLY REQUIRED; MANAGEMENT HAS TO BE

ADAPTED

4

5

The process followed to extract wetlands from high resolution images is described below:

Extracted data layer finally compared with the vector data extracted from the 1:10,000 scale topo sheets and corrected and verified by taking GPS points.

6.0 Outcome of the Study

The results of the study demonstrate that the areas with high values and the quadrants they belong. The areas belongs to the value scale of Level 5, 4 and 3 and falling within quadrant B and D categorized as preservation urgently required zone. The areas has value scale of 1 & 2 falling quadrant C and A could be categorized as potential areas for Urban Development activities. Accordingly, wetlands zonation plan was prepared. The new legislations were introduced for each zone and included each and every Development Plans prepared for the urban areas within the Colombo District. There were five zones,

1. Wetland Protection Zone 2. Wetland Nature Conservation Zone 3. Wetland Agricultural Zone 4. Special Paddy Cultivation Zone and 5. Low – Lying Potential Development Zone.

7.0 Conclusion

The usage of advanced technologies such as ERDAS, ArcGIS to extract features from high resolution images provide benefits to the urban planners to reach some decision on rapid urban expansion and thus effects to the environment. This should be encouraged further more among people and general public.

References

1. Urban Development Authority; “Colombo Metropolitan Development Plan, May 1998, (CMR) 2. Urban Development Authority; “Colombo Megapolis Regional Structure Plan, July 2004(CMRSP) 3. Central Environmental Authority, :Wetlands Master Plan”, October 1994 4. Manishika Jain; May 2009; GIS and Remote Sensing for Urban Sprawl and Planning 5. L H Indrasiri; 2005; Urbanization & Urban Redefinition.