Abstract:
The old city of Sukhothai is one of the most important former capital city of Thailand dating back to more than seven centuries ago. The area is richly densed with archaeological sites which are preserved in good condition. The government of Thailand is planning to further restore it to a national historical park. However, flood which might occur at the old Sukhothai city is a natural harzard that may cause the damage to the archaeological remnants. Therefore a good flood protection system is required. Past hydrological study of storm runoff resulting from rainfall showed that the floodwater came from the mountainous area of the west of the city of Sukhothai and from the inner parts of the old Sukhothai city. Since, the direct runoff at the old city has not been measured before, the surface runoff is predicted from the probable maximum precipitation using the method of instantaneous unit hydrograph and converting it to the probable maximum flood hydrograph.Flood protection system capable of protecting city against the 100 years flood selected in this study employed the method of providing flood storage and draining the excess storm runoff to the nearby watercourses. The improvement of the old drainage canals and storage basins such as ancient ponds within the city limit to increase the efficiency of storing floodwater is required. Since, within the old city, the area is richly densed with the archaeological site and if the canals and storage basins are to be reconstructed outside the city limit, the floodwater within the area may damage the ruins. The excess storm water is the drained through the channelling spillways provided to the water channel outside the city. Perimeter bund is called for to keep away the floodwater from outside the city.