Before a bridge is constructed, a suitable site is selected based on certain factors which have bearing on the economy and stability of the bridge.
Consideration selection bridge construction site
1. At bridge site, the reach of the stream should be straight.
2. The site should be geologically sound i.e. it should be away from fault zone and should have unyielding, non-erodible foundation for abutments and piers.
3. At the site, the stream should be narrow with well defined and firm banks.
4. At site, the river flow should be without whirls and crosscurrents.
5. At the site, there should be suitable high banks above high flood level on each side.
6. The approaches should be economical. They should not be very high or long or liable to flank attacks of the river during floods. They should be free from obstacles such as hills, frequent drainage crossings, built up areas, sacred areas as graveyards, or troublesome land acquisition etc.
7. The site should be at the reasonable proximity to a direct alignment of the road to be connected.
8. There should be no sharp curves in the approaches.
9. The absence of costly river training works, where they are unavoidable they should be executed in dry as far as possible.
10. Avoidance of excessive underwater construction work.
11. If it is unavoidable, the necessity for the approaches of the bridge to cross the spill zone of a river, they should (while processing through the spill zone towards the river), face downstream and not upstream. Facing up stream will cause heading up, pocket formation, and danger to the approaches.