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P. Sreeja and S. Singh
Keywords River hydraulics · Local scour depth · Clear-water scour · Saraighat
bridge · Bridge piers
1 Introduction
Scour at a bridge pier is the formation of a hole around the pier due to erosion of soil
by flowing water [1]. The scour depth around the bridge piers may vary depending
upon the flow depth, angle of attack, pier size, pier shape and characteristics of
the sediments. Numerous researchers have studied the scour mechanism but mostly,
the model studies were made with lot of simplifications and empirical formulas
associated with it [2]. But field investigations in this area are needed to understand
the actual scouring mechanism. Such a study would be helpful in the efficient design
of bridge foundations and strengthening of bed material if required.
1.1 Critical Appraisal of the Reviewed Literature
In laboratory model studies, internal flow characteristics do not truly represent prototype bridge pier scouring in rivers in view of large-scale distortion of the models [3,
4]. Hence, there is a need to evaluate the applicability of empirical scour equations
to different site conditions and check its generality. There is also a need to evaluate
whether the predicted maximum scour depth results in highly uneconomical and over
conservative results.
1.2 Objective of the Study
The present research is concerned with the study of local scour around a bridge pier.
The main aim of the study is to understand the scouring pattern for a river-bridge
system in India (Saraighat Bridge, Guwahati). To address this objective, the present
research has the following scope:
1. To model the river reach under unsteady flow conditions using computer software
package HEC-RAS.
2. To critically evaluate the empirical equations for scour depth determination for
its generality.
2 Methodology
The primary concern is pier scour which is calculated using one dimensional model
(Hec-Ras) for high flood discharge. Aggradation and degradation are long-term
P. Sreeja and S. Singh
Keywords River hydraulics · Local scour depth · Clear-water scour · Saraighat
bridge · Bridge piers
1 Introduction
Scour at a bridge pier is the formation of a hole around the pier due to erosion of soil
by flowing water [1]. The scour depth around the bridge piers may vary depending
upon the flow depth, angle of attack, pier size, pier shape and characteristics of
the sediments. Numerous researchers have studied the scour mechanism but mostly,
the model studies were made with lot of simplifications and empirical formulas
associated with it [2]. But field investigations in this area are needed to understand
the actual scouring mechanism. Such a study would be helpful in the efficient design
of bridge foundations and strengthening of bed material if required.
1.1 Critical Appraisal of the Reviewed Literature
In laboratory model studies, internal flow characteristics do not truly represent prototype bridge pier scouring in rivers in view of large-scale distortion of the models [3,
4]. Hence, there is a need to evaluate the applicability of empirical scour equations
to different site conditions and check its generality. There is also a need to evaluate
whether the predicted maximum scour depth results in highly uneconomical and over
conservative results.
1.2 Objective of the Study
The present research is concerned with the study of local scour around a bridge pier.
The main aim of the study is to understand the scouring pattern for a river-bridge
system in India (Saraighat Bridge, Guwahati). To address this objective, the present
research has the following scope:
1. To model the river reach under unsteady flow conditions using computer software
package HEC-RAS.
2. To critically evaluate the empirical equations for scour depth determination for
its generality.
2 Methodology
The primary concern is pier scour which is calculated using one dimensional model
(Hec-Ras) for high flood discharge. Aggradation and degradation are long-term