Option of geodetic development on flood management

The following paragraph is dealing with considerations of impact factors on the flood prevention of the new artificial Chao Phraya River.

For this research, the planning and design guideline of the new artificial river can be divided into three main data-sets which consider physical conditions, social community participation and environmental impacts:

1) High resolution satellite TanDEM-X Science DEM (German Aerospace Center; DLR)

2) High density and built-up areas

(Public Works and Town & Country Planning, Thailand) 3) Forest covering and land use

(Royal Forest Department, Thailand)

For the final stage, the research anticipates creating a new artificial Chao Phraya River with geodetic approaches and environmentally beneficial landscape.

Additionally, the integration of effective land and water long-term plans will provide increased ability for flood adaptation for communities in Thailand.

 DEM Analysis of the new artificial river (See Appendix 4)

DEM Analysis of the new artificial river has improved elevation intervals information. The low-lying areas are shown in smaller intervals while the higher areas have less precise intervals.

This is necessary to determine the low differences in the terrain of the plain area of central Thailand. For this research, the higher areas are not of particular interest; hence, grading of the higher intervals has no impacts on the preciseness of the map (Map. 6.1).

The results of the flow analysis were used in the creation of the map (Map 6.2). The simulated water streams are shown which are flowing from high areas to low areas. At the confluence of two streams they do combine to form a larger river line. The bright pink lines show low water flows while the pink lines stand for a higher flow and the dark pink lines for the highest possible water flow. The data (grey dots) show human settlement areas.

Map (Map 6.3) illustrates the same results of the flow analysis; however, it considers the forest areas (in green) instead of the human settlement areas (as above). It can be seen that in the area of research, less noteworthy forest areas are omitted. This indicates, that in the planning of the new artificial river channel the consideration of forested areas is deemed irrelevant.

The above results from Map 6.4 were combined and lead to the first design of the new artificial river. For these calculation the DEM data of the DLR was used (Resolution 12 m). The line (red) is demonstrated in the map. The first section of the new river channel starts below Nakhon Sawan and flows until Ayutthaya (153.22 km; section 1).

The second section (Map 6.5) leads from Ayutthaya to the shoreline (122.99 km to the Gulf of Thailand). Along this line, the new river line has to avoid areas of high density human settlements, which are numerous around the mega-city Bangkok.

Map 6.6 illustrates both sections on a satellite image of the Central area of Thailand. The length of both sections combined is 276.21 km.

Hereby, the technical DEM analysis can create the lowest track of the river while the socio-economic factors attempt to avoid housings and human settlements; together with environmental concepts which are carefully protecting forests in the prevention area. After the map, the research will explain the cross section design and construction of the new artificial river.

Map 6.1 Digital Elevation Model (DEM) / Terrain high resolution of DLR in case study area

“Geodetic Support for Flood Risk Management in Thailand with Prevention and Adaption Methods”

Map 6.2 High density area of Central area of Thailand

“Geodetic Support for Flood Risk Management in Thailand with Prevention and Adaption Methods”

Map 6.3 Forest area of Central area of Thailand

“Geodetic Support for Flood Risk Management in Thailand with Prevention and Adaption Methods”

Map 6.4 The first section of the optional channel of the New Artificial Chao Phraya River from Nakon Sawan to Ayutthaya

“Geodetic Support for Flood Risk Management in Thailand with Prevention and Adaption Methods”

Map 6.5 The second section of the optional channel of New Chao Phraya River from Ayutthaya to Gulf of Thailand

“Geodetic Support for Flood Risk Management in Thailand with Prevention and Adaption Methods”

Map 6.6 Overview of the New Chao Phraya River

Section 1

Section 2

“Geodetic Support for Flood Risk Management in Thailand with Prevention and Adaption Methods”

Low density (Nakhon Sawan)

~ 111.83 people/km²

Medium density (Ayutthaya)

~ 316.32 people/km²

High density (Bangkok) Suburb: ~ 1347.11 people/km² City: ~ 3616.64 people/km²

The population along the new artificial river, has been considered in the design of the river construction. The population data was retrieved from the National Statistic Organization Thailand (2012). The population density can be divided into three levels: low, medium and high. The new artificial river line attempts to avoid high density areas as good as possible.

Map 6.7 Levels of population density along the new artificial river

Figure 6.7 New artificial river convergence with the Pasak River

In the design of the new River the area where the new artificial river channel is crossing the Pasak River has to be considered. Therefore, the only possible economical decision may be to integrate the Pasak River into the new artificial river as a tributary.

The old section (present Pasak River) where the Pasak River flows into the Chao Phraya River can be used as a water retention area that also serves communities by collecting surface- and groundwater (See the figure on the next page). Also, a significant amount of biosphere can be preserved ecologically with flora and fauna.

The design of the new artificial river line is crossing the existing Pasak River

Before After

Figure 6.8 Suggestion for the Pasak water retention area

Due to the additional water discharge of the Pasak River, the capacity of the new artificial river has to be designed for that discharge.