Using a Scenario‐Neutral Framework to Avoid Potential Maladaptation to Future Flood Risk

Abstract

This study develops a coherent framework to detect those catchment types associated with a high risk of maladaptation to future flood risk. Using the “scenario‐neutral” approach to impact assessment the sensitivity of Irish catchments to fluvial flooding is examined in the context of national climate change allowances. A predefined sensitivity domain is used to quantify flood responses to +2 °C mean annual temperature with incremental changes in the seasonality and mean of the annual precipitation cycle. The magnitude of the 20‐year flood is simulated at each increment using two rainfall‐runoff models (GR4J, NAM), then concatenated as response surfaces for 35 sample catchments. A typology of catchment sensitivity is developed using clustering and discriminant analysis of physical attributes. The same attributes are used to classify 215 ungauged/data‐sparse catchments. To address possible redundancies, the exposure of different catchment types to projected climate is established using an objectively selected subset of the Coupled Model Intercomparison Project Phase 5 ensemble. Hydrological model uncertainty is shown to significantly influence sensitivity and have a greater effect than ensemble bias. A national flood risk allowance of 20%, considering all 215 catchments is shown to afford protection against ~48% to 98% of the uncertainty in the Coupled Model Intercomparison Project Phase 5 subset (Representative Concentration Pathway 8.5; 2070–2099), irrespective of hydrological model and catchment type. However, results indicate that assuming a standard national or regional allowance could lead to local over/under adaptation. Herein, catchments with relatively less storage are sensitive to seasonal amplification in the annual cycle of precipitation and warrant special attention.

Nonstationary weather and water extremes: a review of methods for their detection, attribution, and management

“…Such frameworks promote early engagement with the decision-maker in the design process, to identify key system vulnerabilities, performance criteria and trade-offs between management goals (Poff et al, 2016). Furthermore, so-called 'scenario-neutral' methods can establish when and where national safety margins for nonstationary hydroclimatic conditions might be inadequate (Prudhomme et al, 2010;Broderick et al, 2019). When combined with storylines that describe more elaborate scenarios of change -such as forest die-back and dust on snowpack under hotter-drier conditions shifting the volume and timing of runoff -more holistic capture of nonstationarity in adaptation planning is then feasible (e.g.…”

Risks and opportunities for a Swiss hydropower company in a changing climate

“…Groupe E pointed out that, given their situation, this type of visual is limited as it is too simple to display the numerous considerations influencing the concession renewal. Instead, Figure 5 in Broderick et al, (2019) basis for Figure 8 to succinctly visualize changes in a series of key indices in relation to thresholds prescribed by the Groupe E. A summary table of the main opportunities and adaptation options was also provided to Groupe E (Table 4).…”

“…Given the costs associated with addressing and preparing for climate change impacts, it is essential to minimize the risk of maladaptation (i.e. inappropriate reaction to a threat) resulting from a misunderstanding of end users' vulnerabilities to climate change or from ill-designed projections (Broderick et al, 2019). Robust adaptation measures that provide benefits under a range of climate change scenarios are especially valuable, given the reduced chance for maladaptation.…”

Mapping the Sensitivity of Population Exposure to Changes in Flood Magnitude: Prospective Application From Local to Global Scale

“…To overcome the uncertainties and problems associated with model cascades, alternative approaches are currently being developed (Guo et al, 2017;Knighton et al, 2017;Kim et al, 2018;Broderick et al, 2019;Keller et al, 2019a;Keller et al, 2019b). In studies investigating the impacts of climate change on hydrology, a scenario-neutral approach has been used to analyze the sensitivity of river flows to changes in temperature and precipitation, where the observed rainfall and temperature data are modified by stepwise increases or decreases in the value of associated parameters.…”