FLUVIAL HYDRAULICS AND HYDRAULIC RISK MITIGATION
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- Versione italiana
- Academic year
- 2022/2023
- Teacher
- LEONARDO SCHIPPA
- Credits
- 9
- Curriculum
- AMBIENTALE
- Didactic period
- Primo Semestre
- SSD
- ICAR/01
Training objectives
- The course treats the main concepts concerning flow in natural stream, flood routing, and sediment laden flow and river morphodynamics. The course also treats river training oriented to hydraulic risk assessment and management, and river restoration.
The main purpose of the course consists of living to students the bases to face the study of flood routing, also referring to mathematical and numerical modeling, and hydraulic structures designing in natural river also accounting for sediment transport.
Moreover the course leads to living to students the bases to acquire the proper skill managing energy, momentum and mass balances governing the open channel flow in practical hydraulic engineering.
The main knowledge that should be acquired is the following:
• Hydrodynamics properties of open channel flow in natural stream, especially referring to complex river geometry and flow resistance elements;
• Mathematical modeling of flood routing;
• Effects of infrastructures (e.g. bridge) on backwater and effects of the flow on the hydraulic structures (e.g. scouring);
• Sediment mass balance and sediment transport formulae;
• Mathematical modeling of river morphodynamics;
• River training techniques;
• Hyperconcentrated flows (i.e. debris and mud flows).
The main skills to be acquired are:
• Flood routing and backwater calculation in natural stream;
• Hydraulic risk mapping;
• Sediment transport evaluation;
• Analyzing and predicting river evolution process;
• Designing hydraulic structures for river restoration. Prerequisites
- It is necessary to have understood and assimilated the main contents of Hydraulic course, particularly referring to uniform and steady open channel flow. The following expertise are requested:
• Differential and integral calculus;
• Mechanical balances of forces and moments, of momentum and angular momentum, potential, kinetic and total mechanical energy; Course programme
- 90 hours of frontal lectures are planned, consisting of theoretical lectures, practical and numerical examples. A practice exercise consisting of hydraulic risk analysis and mapping is provided together with river restoration design. The practical aspects related to mathematical modeling and hydraulic designing are deepened and explained.
Course topics are:
INTRODUCTION AND OPEN CHANNEL FLOW GENERALITY (2,5 hours)
Fundamentals of open channel flow. Energy aspects of open channel flow: specific energy. Subcritical and supercritical flow. Momentum balance and dynamical force.
RIVER GEOMETRY AND ITS EFFECTS (2,5 h)
Fluvial control cross-section. Variable bed slope. Flow obstructions.
RESISTANCE LAW (10 h)
Stress and velocity distribution in open channel flow. Resistance laws. The effects of compound channel and vegetation on the resistance law.
BALANCE EQUATIONS (5 h)
Mass and momentum balance equations in natural stream in presence of lateral inflow, non prismatic channel and compound channel. De St. Venant equations. Conservative form of momentum balance equation.
KYNEMATICS OF OPEN CHANNEL FLOW (2,5 h)
Kinematics characteristics of subcritical and supercritical flow regime. Celerity of propagation of small perturbation.
STEADY FLOW (5 h)
Steady flow equation and numerical methods.
UNSTEADY FLOW IN OPEN CHANNEL AND FLOOD ROUTING (10 h)
Method of characteristics. De St. Venant equation. Finite difference method.
Kinematic model. Diffusive model. Celerity and attenuation of flood. Loop rating curve.
FLUVIAL MORPHODYNAMIC (2,5 h)
Morphodynamics at different scale and river morphological equilibrium.
INCIPIENT MOTION CRITERIA AND SEDIMENT TRANSPORT (10 h)
Incipient motion criteria; non dimensional analysis and Shield diagram. Bed-load, suspendend load and wash-load. Sediment transport formulae. Convective-diffusive equation for suspended sediment.
BED FORMS AND THEIR EFFECTS (5 h)
Bars, dune, ripples and antidune: geometrical-hydraulical characteristicsre and dynamics. Resistance law in presence of bed form.
MORPHODYNAMIC RIVER MODELLING AND RIVER BEND (5 h)
Celerity of propagation of flow and bed perturbation. The fully dynamic model. Semplified models: simple wave model and parabolic model. Kinematics of river bend flow and stress distribution.
COMMUNITY AND NATIONAL LEGISLATION IN SUBJECT OF RIVER AND HYDRAULIC HAZARD (2,5 h)
Community and national rules.
RIVER TRAINING TECHNIQUES AND FLOOD CONTROL (7,5 h)
Check-dam techniques and designing. Dissipation of jets beneath the dam: river bed revetments and energy dissipation basin. Dikes, and slope revetments: techniques and designing criteria.
Levee. Seepage control. Designing criteria for levees and embankement. Effects of channel lining on river bed equilibrium.
DAM BREACH (2,5 hours)
Breach initiation in embankement and dam. Mathematical and numerical breach modeling.
HYPERCONCENTRATED FLOWS AND DEBRIS_FLOWS (2,5 hours)
Hydraulic risk related to debris-flow events. Dynamics of debris flow. Quantification of debris-flow volume and deposition. Kinematic 1-phase model of debris-flow.
PRACTICE EXERCISE (15 hours)
The exercise leads to hydraulic risk mapping of a river crossing an urbanised area.
The following materials are supported:
• Map survey of the area;
• Design discharge value;
• HEC-RAS software (hydrodynamic modelling).
The students are requested to:
• Implementation of river geometry;
• Hydraulic simulation of the scenario related to the design discharge;
• Designing hydralic risk mapping;
• Individuation and designing river restoration works;
The exercise is carried out in classroom and it is supported by the teacher. Didactic methods
- The lectures are organized as follows.
• Frontal lectures concerning the described topics;
• Practical examples, that are devoted to explain engineering applications of theoretical concepts;
• Support to carry out practice exercise (including model implementation, and designing activities). Learning assessment procedures
- The main purpose of the final examination consists of verifying the proper achievement of the previously defined training objectives.
The exam consists of an oral examination.
The oral examination is based on the topics of course. Typically the exam refers to 3 main topics:
1. Open channel flow in absence of sediment transport.
2. Sediment transport and sediment mass balance in natural stream;
3. Comments on the practice exercise carried out during the course and river restoration techniques.
The final mark is expressed as a fraction of 30 and it corresponds to a global evaluation of the test. If the candidate retreats during the examination must repeat the entire test. Reference texts
- Reference books:
-Open-channel hydraulics, R. French, McGraw-Hill International Ed.
-Principles of river hydraulics, A. Armanini, Ed. Springer Company; Malabar, Florida
In-depth books:
- Open channel flow (2nd edition), M. Hanif Chaudry. Springer Ed.
-Fluvial Processes (2nd edition), Ferreira da Silva A.M., Yalin M.S., IAHR Monograph, IAHR Monograph, Ed. CRC Press Balkema book
-Fluvial Processes: Solutions Manual. M.Selim Yalin and A.M.Ferreira da Silva;IAHR Monograph, IAHR, Delft, The Netherland
-Fluvial Processes: Solutions Manual
by M.Selim Yalin and A.M.Ferreira da Silva;IAHR Monograph, IAHR, Delft, The Netherland
Supplementary documentation
- slides provided by the lecturer
