CENV6164 River Engineering

Module Overview

Rivers and estuaries provide people with food, water, energy, communication paths and ports. However, they can also cause major damage through flooding. Understanding and engineering rivers is thus immensely important. River beds are composed of granular material that can be displaced by the water flow and transported from one location to another. Quantitative prediction of sediment erosion and accumulation rates is crucial for many applications in Civil and Environmental Engineering, including dam silting and bridge scouring, to name just a few. Furthermore, fluvial sediment transport can result in the formation of large bed-forms (e.g. ripples, dunes), which, along with the aquatic vegetation present in many natural streams, need to be accounted for in order to quantify flow resistance, which is of great relevance when designing river embankments to contain flood events. This module covers aspects of fluid and sediment mechanics that will allow you to critically assess the stability of a river bed and effectively design a variety of river engineering works.

Aims and Objectives

Module Aims

The general aim of this module is to introduce the students to the theory of fluvial dynamics (which includes fluid and sediment mechanics) and its application to solve relevant problems in river engineering. The emphasis of the module is on providing students with the knowledge and skills that will allow them to address successfully any problem they may encounter as river engineers.

Learning Outcomes

Knowledge and Understanding

Having successfully completed this module, you will be able to demonstrate knowledge and understanding of:

Qualitative behaviour of river and estuarine dynamics (e.g. river meanders)
Relevant hydrodynamic equations of open channel flows
Sediment transport mechanics and modelling approaches
Design notions of the most common river engineering works
Numerical models used in river engineering

Subject Specific Intellectual and Research Skills

Having successfully completed this module you will be able to:

Critically analyse the fundamental equations of fluid dynamics and appreciate how they relate to approximate equations commonly employed in the study of open channels
Appreciate the importance of bed shear stress in open channels, particularly in connection to sediment transport
Identify the coupling between turbulence and sediment dynamics in fluvial environments
Utilise the principle of sediment-mass balance to predict the evolution of the river bed (morphodynamics)
Identify the most appropriate theoretical and practical tools for solving a given problem of engineering interest in rivers

Transferable and Generic Skills

Having successfully completed this module you will be able to:

Problem analysis and problem solving
Team work
Report writing
General theory of fluid dynamics
Knowledge on numerical modelling

Subject Specific Practical Skills

Having successfully completed this module you will be able to:

Determine river bed/banks stability and propose diverse alternatives for river training
Quantify bed-form and grain roughness effects on flow resistance
Identify different modes of sediment transport and quantify their rates as functions of hydraulic variables
Estimate the rate of siltation in a given dam
Critically assess local and general scour around bridge foundations
Use numerical models to predict the morphological evolution of a river
Use numerical models to assess the impact of flood events and dam breaks
Exercise technical judgement and make decisions
Carry out and present engineering calculations

Syllabus

INTRODUCTION Historic importance of rivers and estuaries; General overview of rivers in the world; Qualitative behaviour of the river-estuary system; Classification of rivers. OPEN CHANNEL HYDRODYNAMICS Revision of basic concept of fluid dynamics (e.g. conservation laws, viscosity, drag, etc.); Basic equations of fluid dynamics (Navier Stokes) and their useful simplifications for open channels (e.g. the Shallow Water equations); The velocity profile; Introduction to turbulence; Bed shear stress; Steady and unsteady flow. SEDIMENT TRANSPORT Modes of sediment transport (bedload and suspension); Key sediment parameters (diameter, grain size distribution, etc.); Fundamental mechanics of sediment motion; Initiation of motion (Shields criterion); Empirical estimates for sediment transport rates; Bedforms; Sediment transport modelling; Suspended sediment concentration (the Rouse profile); Bed evolution modelling (Exner equation). RIVER ENGINEERING WORKS River training; Design of stable channels; Water level control; Introduction to ecohydraulics and ‘green engineering’; Dam siltation; Bridge pier and abutment scour; Flood control; Introduction to river navigation and hydropower; Dam break. NUMERICAL MODELLING Overview of numerical modelling in river engineering; Introduction to numerical modelling (finite differences); Discussion of different mathematical models and their pros & cons (steady vs unsteady, 1D vs 2D vs 3D, fixed vs mobile bed, etc.); Overview of available free and commercial software for river engineering; Computer labs.

Special Features

None

Learning and Teaching

Teaching and learning methods

The module consists of conventional lectures, computer labs (tutorials on numerical modelling), one hydraulic laboratory session and occasional lectures by guest speakers.

Type	Hours
Follow-up work	15
Wider reading or practice	25
Completion of assessment task	20
Tutorial	4
Independent Study	50
Lecture	36
Total study time	150

Resources & Reading list

Tritton D.J. (2007). Physical Fluid Dynamics.

MaysL.W (2001). Water Resources Engineering Wiley.

Graf W. H. (1971). Hydraulics of Sediment Transport.

Assessment

Formative

Laboratory Assignment

Summative

Method	Percentage contribution
Coursework	20%
Exam	70%
Quizzes (10 minutes)	10%

Referral

Method	Percentage contribution
Exam	100%

Repeat Information

Repeat type: Internal & External

Linked modules

Pre-requisite: CENV2008 Hydraulics