An Approach to Flooding Risk Management by Integrating Ecosystem Functions and Services. Case of Study: La Presidenta Watershed (Medellin, Colombia)

Climate variability and climate change, joined to fast variations in surface covers, have become substantial topics to explain the increasing amount of floodings in urban and peri-urban watersheds in the Andean Region of Colombia. Therefore, in a local scale, with a still short knowledge of the physical phenomenon related to climate change, decision makers search for technical tools to support future interventions in the context of the local territorial management, by means of planning strategies involved in the Integrated Water Resource Management – IWRM - scope (this last, adopted as a national policy). In the present research, a simplified model for the assessment and mitigation of flood risk based on improvements of flows of a local relevant new ecosystem service related to this risk is exposed. Ecosystem functions as conservation of percolation zones, water retention by vegetation and urban water infrastructures for the control of surface runoff are fitted together in this new frame of ecosystem service, coupling it into a GIS that also includes an appropriate DEM (generated from topographical contours in scales of 1:5000 and 1:12000) and information coming from remote sensoring. For a set of maximum values of precipitations associated to different return periods, translated into the ground by flooding maps, some scenarios of vulnerability for possible future states of the ecosystem service proposed in the case of analysis (La Presidenta Watershed, Medellin, Colombia) are shown. For each of them, flood risk zones are generated by using Fuzzy Logic, which allows to capture the expert knowledge needed in this part of the methodology. These results depict the effects of different cover changes over the ecosystem service final amount, and their correlation with the floodings expected in some areas of the watershed. Final conclusions are also included, comprising the proposal of diverse planning strategies over this territory, in order to manage the flows of the ecosystem functions and the ecosystem service addressed. This initial approach becomes a useful tool for local territorial planners involved in water resource management, who can subsequently fund diverse plans required in some phases of the IWRM.

Keywords: Flooding Risk, Management Ecosystem Functions and Services, percolation zones, water retention by vegetation and hydraulic structures for the control of surface runoff, Territorial Management, IWRM.