Geomorphological Analysis of Streams for Support of Early Flood Warning Systems

The department of Caldas in Colombia is located in the mountainous area of the Andes, is characterized by a varied topography with many water resources that flow into the Cauca and Magdalena rivers (the most important in the country). The department of Caldas is prone to landslides in the upper part of basins, as well as sudden and slow floods, thus it is necessary to know the behavior of the streams in detail. Additionally, rainfall events in the department increase river levels, triggering erosion at the headwaters of basins and dragging sediments of different sizes, which not only carry a considerable liquid but also solid flow; in areas of low slopes, the river expands causing floods in the settlement of the valley.

Knowledge of geomorphologic characteristics as changes in channel geometry during floods, variations in levels, flow regimes, erosion and sedimentation processes which in turn change river shape, affecting the nature and frequency of floods is greatly important in the implementation of early flood warning systems.

This study proposes the geomorphological characterization of 3 streams in the department of Caldas where between 4 or 6 flow measurements were made at different stream points in the period 2017-2018. The Fryis and Brierley methodology was used with satellite images in which each river was classified through parameters such as the entrenchment relationship, the width / depth ratio, the sinuosity, the slope and the valley.

As a result of this study, it was found that all rivers could be classified into 9 different sections (steep head waters, streams, occasional floodplain pockets, discontinuous floodplains, braided, meandering active, meandering passive, anastomosis and canalized). The information obtained with this classification will be a support to understand in detail the behavior of rivers, know the frequency of extreme events, the impacts they can generate and find the depth at which an early flood warning system could be activated. In addition, it will provide authorities with resources to make decisions on watershed planning and management.