Qgis riberbanks tools

A simple tools for analysis of banks of a river in Qgis; algorytms and scripts are written with Qgis 3 graphical modeler and Python.

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Table of content

1. How to use on qgis
2. Confined Valley Index
3. Riverbanks Distance
4. Riverbanks Distance Comparison
5. Disclaimer and Credits

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How to use on Qgis

Download the specific model3 files in this repository: all model3 files are running on Qgis 3.28.11 or higher

• Confined Valley Index
• Riverbanks Distance
• River Banks Distance Comparison

NOTE: If you download file directly from GitHub webpage may assure that the extension of file must be .mopdel3 for properly use in Qgis

1. Open Qgis (developed and testet with Qgis 3.28.11)
2. Go to Processing sidebar and go to Model icon menu
3. Click on "Open existing model" and select the file in your filesystem

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Confined Valley Index

v. 1.1 (December 2023)

DOWNLOAD PDF schema

Description

The algorithm is used to calculate the relationship $C_{Vi}$ between the width of the ValleyBottom $VB_W$ and the banks of a river $RB_W$.

$$ C_{Vi} = {{VB_W} \over {RB_W}} $$

Input data

Parameter name	Data Type	Description
LEFT River Bank	Vector Line	Line of the Left bank
RIGHT River Bank	Vector Line	Line of the Right bank
River Line	Vector Line	Path of the river
Transects STEP	Integer	distance in meters along the path used for creating transects
Transects WIDTH	Integer	Lenght in meters of transects across river path
Valley Bottom	Polygon	Polygon features that define the Valley Bottom of the river

Transects are generated, at constant distance from each other along the path, along the river axis; they intersect the right bank, the left bank and the ValleyBottom polygon. The distances between the river axis and the intersections are calculated, the minimum value is taken.

Output

In Output a Vector Points along the river axis containing the calculated data is generated with this attribute table:

Filed name	Type	Desription
SEZ-ID	Int	Transect identifier (key field)
VB_RB-index	Float	$C_{Vi} = {{VB_W} \over {RB_W}}$
RB-W	Float	Bank width
VB-W	Float	ValleyBottom Width
min-RB-R	Float	Minimum distance to the Right bank
min-RB-L	Float	Minimum distance to the Left bank
min-VB-L	Float	Minimum distance to the Left ValleyBottom
min-VB-R	Float	Mimimum distance to the Right ValleyBottom
transect_d	Float	Progressive distance along river path

An example of the results is shown in this map. A scaled-type symbology was used using the VB_RB-index field that represent the CVI. Higher values indicate that the valley bottom is further from the river banks. Therefore, in these portions the river is not confined by resistant elements.

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RiverBanks Distance RBD

--> Download Qgis model3 file

RBD Description

distance between banks and axis of a river along path; useful for morphological analysis.

Centerline of the river is simplyfied into fixed-lenght segments, for each step along the path this model get the distance between centerline and left/right banks.

Here how it works:

1. Create nodes along river centerline path, using the input "step"
2. Assign a key-value for each nodes called "SEZ-ID"
3. Create a new simplified river centerline using nodes
4. Create transect across simplified river centerline
5. Make a spatial-join with transects and nodes and assign the key-value "SEZ-ID" to transects
6. Create nodes of intersection between Transects and banks (Left/Right)
7. Add coordinates X/Y of intersection into attribute table
8. Spatial join of intersection nodes and Transects, and then assign attribute
9. Calculation of distances (Left and Right) using attribute data
10. Field cleaning and output.

RBD Input data

Parameter name	Type	Description
Left Riverbank - RB-L	Linestring	Left bank vector, must contain 1-line feature
Right Riverbank - RB-R	Linestring	Right bank vector, must contain 1-line feature
River centerline	Linestring	Path of river
Step	Integer	Distance in meters along river path from a node to another (*)
Transects width	Integer	Width in meters used to generate transects (**)

(*) A too short step increase computational resource needs and accuracy of data. A too long step decrease accuracy of the output parameters that describe morphology of the river

(**) This value must be large enough, equal to at least twice the maximum distance at which the bank could be to intersect banks. It is used to generate transects orthogonal to the river simplified centerline

RBD Output

This model generate the Transects vector features along path of the river, and intersection nodes. For each transect in attribute table there are Right and Left distance from centerline, useful to calculate banks width.

Filed name	Type	Description
SEZ-ID	Int	Transect identifier (key field)
min-RB-R	Float	Minimum distance to the Right Bank
max-RB-R	Float	Maximum distance to the Right Bank
min-RB-L	Float	Minimum distance to the Left Bank
max-RB-L	Float	Maxinum distance to the Left Bank

null value distance is for no intersection between transects and RB

This image is an example of map output. linestring in red are the RB in input, the blue line is the river Centerline

Riverbanks Distance Comparison RBDC

--> Download model3 file

The bank distance comparison model (RBDC) is an implementation of RBD with two banks, which is useful in historical comparison analysis or quantitative analysis of the width of river banks in two epochs.

RBDC Input data

Parameter name	Type	Description
River centerline	Linestring	Path of river
Step	Integer	Distance in meters along river path from a node to another (*)
Time 1 Left Riverbank - T1-RB-L	Linestring	Time 1 Left bank vector, must contain 1-line feature
Time 1 Right Riverbank - T1-RB-R	Linestring	Time 1 Right bank vector, must contain 1-line feature
Time 2 Left Riverbank - T2-RB-L	Linestring	Time 2 Left bank vector, must contain 1-line feature
Time 2 Right Riverbank - T2-RB-R	Linestring	Time 2 Right bank vector, must contain 1-line feature
Transects width	Integer	Width in meters used to generate transects (**)
Revert-path-direction	Boolean	if checked assignment order of "SEZ-ID" is reverted along path

(*) A too short step increase computational resource needs and accuracy of data. A too long step decrease accuracy of the output parameters that describe morphology of the river

(**) This value must be large enough, equal to at least twice the maximum distance at which the bank could be to intersect banks. It is used to generate transects orthogonal to the river simplified centerline

RBDC Output

This model generate 2 layers:

1. a line layer called: "T1-T2 Transects RB distance comparison"
2. a point layer called: "Interseciton nodes"

Transects layer contain data about bank distance and their comparison, point layer contain only point of intersection between banks and transects.

The attribute table of Transects layer contain this data:

Filed name	Type	Description
SEZ-ID	Int	Transect identifier (key field)
T1-min-RB-R	Float	Time 1 Minimum distance to the Right Bank: ${r}_{T1}$
T1-max-RB-R	Float	Time 1 Maximum distance to the Right Bank: ${R}_{T1}$
T1-min-RB-L	Float	Time 1 Minimum distance to the Left Bank: ${l}_{T1}$
T1-max-RB-L	Float	Time 1 Maxinum distance to the Left Bank: ${L}_{T1}$
T2-min-RB-R	Float	Time 2 Minimum distance to the Right Bank: ${r}_{T2}$
T2-max-RB-R	Float	Time 2 Maximum distance to the Right Bank: ${R}_{T2}$
T2-min-RB-L	Float	Time 2 Minimum distance to the Left Bank: ${l}_{T2}$
T2-max-RB-L	Float	Time 2 Maximum distance to the Left Bank: ${L}_{T1}$
T2-T1-min-delta-L	Float	$\Delta_l$ = ${l_{T2}}$ - ${l_{T1}}$
T2-T1-min-delta-R	Float	$\Delta_r$ = ${r_{T2}}$ - ${r_{T1}}$

null value distance is for no intersection between transects and RB

This is an example of results in attribute table

This is an example of results in maps

Disclaimer and credits

This repository contains algorithms that for calculating and analyzing some hydrographic features that are useful for analyses on historical course trends and river geometry.

The work was developed within my research at the University of Catania as Phd student, specific through a Scientific collaboration agreement between the Basin Authority of the Hydrographic District of Sicily (AdB Sicilia) and the Department of Civil Engineering and Architecture (DICaR) of the University of Catania, for hydrological and hydraulic studies for the identification of river belts, for the identification of NWRM (Natural Water Retention Measures), and for the definition of lamination plans of the rivers.

List of contributors

• Gianfranco Di Pietro, PhD student at Università di Catania
• Rosaria Ester Musumeci, Associate professor of Hydraulics - Università di Catania
• Valeria Pennisi, Researcher at Università di Catania
• Martina Stagnitti, Researcer at Università di Catania