Friday, February 6, 2026

The Hydrological Modelling 2026 Class

 Welcome to the 2026 Hydrological Modeling Class!

To better understand the materials provided:

  • Storyboards – Summaries of the lectures, usually in Italian.
  • Whiteboards – Explanations of specific topics, presented on a whiteboard using Notability on an iPad.
  • Slides – Commented in English (available since 2021).
  • Videos – Recorded during lectures to complement the slides, with no editing (as post-production would be too time-consuming). The 2026 Vimeo showcase is available at this link. 
  • Additional information & references – Marked in italics, for the curious and the brave who want to explore further.

📅 23 February 2026 

Syllabus & Introduction to Hydrological Modeling

In this session, I introduced the course and its learning-by-doing philosophy. We cover all theoretical concepts first, followed by the practical applications (with Professor Giuseppe Formetta).

The real start 

To begin, it is also worth to have a little (philosophical) analysis of what a model is. This is what is done in the following part of the lecture.

📅 26th February 2026 – Geomorphometry

This session begins with a discussion of previous lesson topics and the rationale behind introducing geomorphometric concepts. Since catchments are spatially extended, understanding their geometry is essential for studying catchment hydrology.

In the first part, we focus on the geometrical and differential characteristics of topography, including:

  • Elevation
  • Slope
  • Curvature

These parameters are fundamental for extracting the river network and identifying different parts of a catchment.

We then define drainage directions and explore how they are computed using Digital Elevation Models (DEMs)—where topography is discretized on a regular grid. From these drainage directions, we determine the total contributing area at each point of a DEM.

These two key characteristics allow us to:

  1. Identify channel heads and extract the river network.
  2. Define hillslopes and establish an initial framework for Hydrologic Response Units (HRUs).
    📅 2nd March 2026 – Geomorphometry
    Hydrological Models. This is a class about hydrological models, so what are they ?

    The title is self-explanatory. A theoretical approach to modelling is necessary because we have to frame properly our action when we jump from the laws of physics to the laws of  hydrology. Making hydrology we do not have to forget physics but for getting usable models we have to do appropriate simplifications and distorsions. The type of model we will use in the course are those in the tradition are called lumped models. Here we also introduce a graphical tool to represent these models.

    📅 9 March 2026 

    Hydrological Models 

    For old material give a look to Hydrological Modelling 2023

    📅 12 March 2026 

     Linear Models for HRUs

    Once we have grasped the main general (and generic) ideas, we try to draw the simplest systems. They turn out to be analytically solvable, and we derive their solutions carefully. From the group of linear systems springs out the Nash model, whose derivation is performed.  Obviously, it remains the problem to understand how much the models can describe "reality". However, this an issue we leave for future investigations.
    A little more on the IUH and looking at the variety of HDSys models

    We introduced previously without very much digging into it the concept of Instantaneous Unit Hydrograph. Here we explain more deeply its properties, Then we observe that there are issues related to the partition of fluxes and we discuss some simple models for obtaining them. Not rocket science here. The concept that we need those tools is more important than the tools themselves. We also observe that linearity is not satisfactory and we give a reference to many non linear models. Finally we discuss an implementation of some of the discussed concepts in the System GEOframe. 

    📅 16 March 2026

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