Learning outcomes of the course unit
Knowledge and understanding:
At the end of the course the student will complete the fundamental knowledge concerning flood hydrology, preparatory to the more practical courses the student will deal with in the second cycle degree in “Civil Engineering” or in “Environmental and Land Management Engineering”.
Applying knowledge and understanding:
At the end of the Course the student will be able to statistically estimate heavy rainfalls and flood discharges, to apply rainfall-runoff models and to determine steady-state flow profiles in rivers. Ultimately, the student will be able to develop a hydrological report, preparatory to river planning projects.
The student should be able to understand, with critical mind, hydrological data and to critically evaluate hydrological reports.
After the examination the student will have acquired a correct use of technical language and should be able to explain in a clear and convincing manner the results of hydrological data processing with the support of technical graphs, tables and texts.
It is useful to have familiarity with EXCEL.
Course contents summary
The main part of the course deals with the methodologies of flood estimation for the design of hydraulic structures and protection plans. The course topics are essential prerequisites for the following courses of Hydraulic structures, River basin management and Hydraulic plants. The last part of the course concerns steady flows in natural rivers.
Module 1 – Hydrologic statistics
Probabilistic treatment of hydrologic data; statistical parameters; probability distributions (log-normal, Gumbel, GEV) and their application in hydrology. Parameters estimation: method of moments and least mean squares. Plotting of experimental data on probability charts. Return period.
Module 2 – Rainfall measurements and elaborations
Non-recording and recording rain gauges; rainfall information collected in the Italian hydrologic annals (part I); time scales of hydrologic processes; Italian rainfall regimes; areal rainfall estimation: Thiessen polygons, isoiethal curves, grid based methods; statistical elaborations of short duration rainfalls: point and spatial depth-duration-frequency curves; areal-reduction factors, design storms
Estimation of depth-duration-frequency curves for all the rainfall stations belonging to a selected watershed.
Module 3 – Hydrological processes.
River basin main characteristics: hypsographic curve, hillside slope, shape factors, Horton-Strahler laws. Excess rainfall estimation (Horton, SCS-CN and index). Measurements of water stages and velocities in rivers: level-gauges, current meters; discharge derivation; stage-discharge relationships; stage and discharge information collected in the Italian hydrologic annals (part II); discharge-duration curves; Characteristics of Italian rainfall regimes; hydrologic cycle: control volume, processes, equations. Time-scales of main hydrological phenomena and return periods for design purposes;
Module 4 –Floods.
Origins and causes of floods in natural rivers; flood hydrograph analysis, base flow separation; rainfall-runoff mathematical description. Linear models: hypotheses and limits, convolution integral, IUH theory; IUH of more than one linear model in series and/or in parallel. Conceptual models: hypotheses and equations; IUH for the linear reservoir model, Nash model, time-area method; parameter calibration of linear models: method of moments and least mean squares.
Baseflow separation techniques and excess rainfall estimation. Calibration of a two-parameters linear rainfall-runoff model by moments and least squares methods. Discharge estimation via discrete convolution equation.
Module 5 – Peak discharge estimation.
Direct methods and regional analysis; indirect methods based on rainfall-runoff models, critical rainfall duration; empirical formulas and order of magnitude for the main Italian rivers.
Annual peak and annual maxima daily discharges analysis and estimation.
Module 6 – Uniform and steady flows.
Mild and steep slope channels; sub- and supercritical flows. Hydraulic jump and its location. Classification and analysis of flow profiles in prismatic channels and natural rivers; abrupt channel transitions: flows through contractions and bottom humps.
Longitudinal profile evaluation on a prismatic channel via direct-step method with subcritical and supercritical flows, hydraulic jump localization.
Slides presented during lessons, class notes, text and data to develop the exercises (Available at lea.unipr.it)
Maione U., “Le piene fluviali”, La Goliardica Pavese, 1995 (Available in Library).
Moisello U., “Idrologia Tecnica”, La Goliardica Pavese, 1998 (Available in Library).
The course is made of Lectures, with Power Point presentations, and exercises in informatics lab mainly with the use of the EXCEL package.
Assessment methods and criteria
The evaluation consists of an oral examination. Two-three questions are put to the student on the arguments developed in the lectures and in the laboratory activities. The student must demonstrate to have acquired the main theoretical concepts and technical terms, to be able to solve problems analogous to those performed during the lectures, to have clear in mind the orders of magnitude and to have acquired enough communication skills. The Student must also demonstrate the ability to make proper connections with other branches of knowledge (mathematics, physics, hydraulics)
The evaluation criteria of the examination are: 40% theoretical questions, 30% practical exercises, 15% communication skills, 15% original applications (independent judgment)