2 IPCC CZMS 1992 Development Factors Development Factors C D Development Factors E F 1 Hirai et al.,1999 Fig.1 Original procedure of assessment of the

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1 LAGUNA LAGUNA 7 p Assessment of Impacts of Sea Level Rise on the Songkhla Lake in South Thailand Yukihiro Hirai 1 Abstract : In this paper the author first presents an original procedure to assess the impact of sea level rise. Following this procedure the natural and socioeconomic characteristics of the Songkhla Lake are described. Then the lacustrine lowland of Thale Sap Songkhla is divided into three distinctive geographical zones, and major factors that control the development of each littoral zone are identified. Based on those development factors, some serious impacts of sea level rise on the lake were assessed as follows ; 1 In the beach ridge plain, coastal erosion will become more severely, especially where large scale shrimp farming developed will affected critically by the retreat of the shoreline along the present coast. 2 The area of Songkhla City should be protected by higher or stronger seawall if the coastal erosion would become more severe. 3 The channel linked the lake and the Gulf of Thailand will become twice or three times as wide as present one, because of the erosion of the north end of the spit. Then the groundwater in the littoral lowlands will be affected by the increase in salinity of the lake water. 4 In the deltaic lowland of Thale Sap Songkhla, wide littoral area will be inundated with lake water about 1 to 3 km in width from the present lake shoreline. Lacustrine lowlands newly covered with urban facilities, should be protected from severe floods or long term inundation. Key words : assessment of impacts, beach ridge plain, deltaic lowland, sea level rise, Songkhla Lake IPCC cm 50 cm IPCC Department of Geography, Faculty of Education, Ehime University Present address ; Department of Geography, Faculty of Literature, Senshu University, Kawasaki , Japan e mail ; hirai@isc.senshu-u.ac.jp 1

2 2 IPCC CZMS 1992 Development Factors Development Factors C D Development Factors E F 1 Hirai et al.,1999 Fig.1 Original procedure of assessment of the impacts of sea level rise on coastal lagoons Hirai et al., a ; 1998 ; 1999 ; Hirai, Sato and Charlchai, Hirai, Sato and Charlchai 1999 IPCC CZMS km 25 km 1182 km 2 Thale Noi Thale Luang Thale Sap Songkhla 3 2 A Beach Ridge Plain B Thale Noi and Phru Khuan Khreng C Lacustrine lowland of Thale Luang D Deltaic

3 Fig.2 Geomorphological classification map of the Songkhla Lake area Hirai,1999

4 4 Lowland of Thale Sap Songkhla km m 2 3 m 1 2 m 4 5 m 26 km km 2 Phru Khuan Khreng m 2100 mm NESDB, mm mm mm mm 1995 a 1.1 m 1.8 m 1.5 m m 1 2 m m 2.5 km Ranot m Thale Noi Waterfowl Park 1 2 3

5 5 3 Fig.3 Geomorphological classification map of Thale Sap Songkhla A B C km 5km m 2km m km km km 3 7 2m 5

6 6 4 Fig.4 Geomorphological cross section of the southern part of the Beach Ridge Plain 2m 3.5 m 1m 1.5 m 0.5 m Ko Nu cm m m 0.6 m 0.5 m m 1m 0.5 m 0.5 m m 1 m 0.5 m 1m m 2.2 m cm 1m m 3.5 m

7 7 5 Fig.5 Geomorphological cross section of the Sand Spit of Songkhla City 1.8 km 5km 2 3 m 3m 20 m m m Wat Rong Was 100 mm m b 1998 City Pillar Traiburi Rd Ramwithi Rd Saket Rd m 4.5 km Samila Beach Ban Kao Seng a m 500 m 2km Laem Son On m 10 m 2.2 m 0.9 m Khlong U Tapao Khlong Bang Klam Khlong Phu Mi

8 m a b c d e 5 Khlong Rang 6km 2 I II m 3 50 m m m 0.5 m 200 m 2.1 m I I 2/3 0.4 m I I 500 m 0.6 m m II I 10 m 2m m 1m 7km I II m Ban Hua Hat 1.2 m 700 m Wat Khlongkha Wadi 1.5 m Pakbung Piper betele 6 Fig.6 Geomorphological cross section of the north western part of Deltaic Lowland of Thale Sap Songkhla

9 9 Chompoo 1km cm cm m 50 m 1m 2 9 Ko MakKo Nang Kham 4km 20 Laem Pho 5km 3km Songkhla Laguna 1km km Melaleuca leucadendra II Development Factors 3 Development Factors cm 1m IPCC m 1m km 2m

10 10 1 Development Factors Table 1 Development Factors of three geomorphological zones of Thale Sap Songkhla 0.5 m 0.5 m 500 m 500 m 2 Development Factors 4 5 Development Factors m Development Factors m 2 3 m 20 NICA National Institute of Coastal Aquaculture m Son, Casualina equisecifolia Prinya, 1993 Development Factors m 1m

11 11 5 Development Factors Development Factors 250 m I m 1.5 m I km II 0.5 m 1m m 1m 0.5 m 1.5 m 7 A1 m 500 m 1 km 1 km 3 km

12 12 7 Fig.7 An assessment map of impacts of sea level rise on Thale Sap Songkhla B 1 m m 2 3 C km

13 13 D 2 IPCC CZMS ; Hirai, Sato and Charlchai, D E Developmet Factors F D 3 5 E Developmet Factors 0.5 m,1 m F A B C D Prince of Songkhla University ; PSU Laboratory of Land Reclamation, Department of Earth Science, Faculty of Natural Resorces Dr. Charlcahai Cha Am Thai Japanese Geological Meeting The Comprehensive Assessments on Impacts of Sea Level Rise 1995 a b 186 p , Hirai, Y., Satoh, T. and Tanavud, C 1999 Assessment of impacts of sea level rise on coastal lagoons case studies in Japan and Thailand. Regional Views, 12, IPCC 1996 IPCC

14 p. IPCC CZMS 1992 Global Climate Change and the Rising Challenge of the Sea, 35 p Data Book of SEA LEVEL RISE,88 p. NESDB National Economic and Social Development Board, and National Environment Board 1985 Songkhla Lake basin planning study, Final Report, vol. 2, Annex A, Physical Natural and Human Resources of the Basin Prinya Nutalaya 1993 Coastal erosion in the Gulf of Thailand. International Congress on Geomorphological Hazards in Asian Pacific Region, Sep Waseda Univ., Tokyo, p.

A: B: C: D: E: a: b: 1: 2: 3: 4: 5: 6: 7: Figure 1. Land-use around the Songkhla Lakes A: Rice field B: Urban area C: Fish/Shrimp ponds D: I

I (Kates et al., 1990) Rigg (1995) (1997) (Srivardhana, 1993) Hirai et al.(1999) 1,182 km 2 Somboon and Paphavasit (1993), (1997), (1995, 1999, 2000) 4 10 km 3 81 14 2001 1 A: B: C: D: E: a: b: 1: 2: 3: