Periodic Reporting for period 1 - FireAndRiskPrevention (When the smoke clears: predicting and preventing catastrophic erosion and flooding after wildfires in volcanic terrains)
Reporting period: 2015-08-01 to 2017-07-31
Major advances have been made in the last decade to support land managers: (i) models to anticipate runoff and erosion events in the post-fire period, such as the Water Erosion Prediction Project model (WEPP, US Forest Service); and (ii) innovative hillslope stabilization treatments aimed at reducing runoff occurrence and erosion events.
Although widespread in the USA, the application of these advances is still in its infancy Europe due to the lack of region- and soil-specific calibration and effectiveness testing, leading in some cases to a risk to lives and resources in particularly vulnerable areas. Population and infrastructure in volcanic regions are usually extremely vulnerable to hydrological and erosional events due to their location in, or downstream of, fire-prone steep slopes, high population density, and the general instability of volcanic terrain. For example, in 2009 a severe erosion event occurred in a fire-affected area in volcanic terrain in La Palma (Canary Islands, Spain) that led to damages to infrastructure (€5 M.) and affected public safety during the first rainstorm after the fire. The lack of adapted models to predict runoff, erosion, and ash transport and knowledge on the effectiveness of post-fire mitigation treatments hinders the ability of managers to predict catastrophic events and protect human lives, infrastructure, and ecosystem services.
This project aimed to fill these knowledge and management gaps by using an innovative field, laboratory, and modelling approach and a carefully chosen implementation programme, involving global leaders in academia, industry and management. This successful collaboration resulted in (i) the validation and calibration of the WEPP model for the volcanic soils of the Canary Islands (Spain), (ii) the evaluation of the effectiveness of three alternative and innovative hillslope stabilization treatments for this terrain type, and (iii) the development of a model prototype to predict ash transport and contamination risk to water bodies.
The effectiveness of four hillslope stabilization treatments was compared for the first time for this terrain type: (i) log erosion barriers, the most common treatment currently used in the Canary Islands and in Spain; (ii) wood shred mulch, a novel method extensively used in USA but not tested for volcanic soils to date; (iii) pine needle mulch, a cheaper alternative to the wood-based mulches due to its lower density and transport costs; and (iv) polyacrylamide (PAM) a synthetic polymer extensively used in agriculture to stabilize degraded soils but not tested in fire-affected volcanic soils. The comparison provided critical knowledge from a management perspective since log erosion barriers and PAM provide limited effect in reducing runoff and erosion processes, whereas pine needle and wood shred mulches showed similarly high efficiency in reducing runoff and erosion. These results have been already transferred to Cabildo de Tenerife and we expect that this impact can be exported to other areas in volcanic terrain.
To address the critical knowledge and management gap regarding the impact of ash on water quality, we have developed the first conceptual model able to predict ash delivery risk and calculate the probability of occurrence of ash contamination events in fire-affected environments. The prototype model, designed in collaboration with Drs. Elliot and Robichaud (US Forest Service), has already been successfully tested using laboratory data. The prototype is now ready to be calibrated and validated for “real life” conditions using field data from key vulnerable ecosystems before being transferred to end-users. This ambitious objective is my next step in research through a recently funded 3-years project and will help me to definitively consolidate my position in science gained through this Marie Skłodowska-Curie fellowship.
The ash transport model prototype we have developed through this project is the first of its type able to predict the probability of ash delivery and contamination risk in the post-fire period. This tool will have a direct impact on society by supporting managers in protecting water reservoirs located in fire-prone or fire-managed areas that, for example, supply 60% of the fresh-water to the 100 biggest cities in the world. Previous contamination events by ash led to expensive treatment expenses exceeding €22 Mill. in Denver (USA; 1996&2002), €25 Mill. in Canberra (Australia; 2003), and €4 Mill. in Belfast (UK; 2011). The model will support water-supply managers in designing, for example: (i) prescribed burn plans and silvicultural activities to reduce potential ash production in vulnerable locations; (ii) post-fire mitigation plans aimed at identifying critical sources of ash and implement actions to stabilize ash in critical areas; and (iii) emergency water treatment procedures to decontaminate water.