Effectiveness of Nature-Based Solutions in Mitigating Flood Hazard in a Mediterranean Peri-Urban Catchment

Abstract

Urbanization alters natural hydrological processes and enhances runoff, which affects flood hazard. Interest in nature-based solutions (NBS) for sustainable mitigation and adaptation to urban floods is growing, but the magnitudes of NBS effects are still poorly investigated. This study explores the potential of NBS for flood hazard mitigation in a small peri-urban catchment in central Portugal, prone to flash floods driven by urbanization and short but intense rainfall events typical of the Mediterranean region. Flood extent and flood depth are assessed by manually coupling the hydrologic HEC-HMS and hydraulic HEC-RAS models. The coupled model was run for single rainfall events with recurrence periods of 10−, 20−, 50−, and 100−years, considering four simulation scenarios: current conditions (without NBS), and with an upslope NBS, a downslope NBS, and a combination of both. The model-simulation approach provides good estimates of flood magnitude (NSE = 0.91, RMSE = 0.08, MAE = 0.07, R2 = 0.93), and shows that diverting streamflow into abandoned fields has positive impacts in mitigating downslope flood hazard. The implementation of an upslope NBS can decrease the water depth at the catchment outlet by 0.02 m, whereas a downslope NBS can reduce it from 0.10 m to 0.23 m for increasing return periods. Combined upslope and downslope NBS have a marginal additional impact in reducing water depth, ranging from 0.11 m to 0.24 m for 10− and 100−year floods. Decreases in water depth provided by NBS are useful in flood mitigation and adaptation within the peri-urban catchment. A network of NBS, rather than small isolated strategies, needs to be created for efficient flood-risk management at a larger scale.

Land-use changes and precipitation cycles to understand hydrodynamic responses in semiarid Mediterranean karstic watersheds

“…The HEC-HMS model is a physics-based one applied to a wide range of cases, such as climate change impacts on water resources (Abbaspour et al, 2017;Azmat et al, 2018;Liu et al, 2020), land management practices on water, sediment transport, and agricultural chemical yields in calibrated and uncalibrated watersheds (Khoi, 2016;Hu et al, 2021). Recent improvements in this computational time model resolution allow us to conduct the simulation with periods in minutes, placing HEC-HMS as a suitable tool even for flash flood studies (Jeong et al, 2010;Rafiei-Emam et al, 2016;Ferreira et al, 2020). The version used in this research was 4.7 and the simulations were run at a daily scale, which was considered an appropriate computational time step according to the 28-year length period simulated in this study.…”

“…Sensitivity and uncertainly analysis (calibration and validation) were performed at a daily scale using the observed flow data from the 8015 stream gauge station to optimize initial values of hydrologic parameters from the HEC-HMS model. This station is located at the outlet of the Guadalest watershed and contains valuable data from 1967 to 2018 (CEDEX, 2021), which complete hydrogram can be found in CHJ ( 2013 The automatic calibration (in this case deterministic optimization) was focused on the most key parameters of the HEC-HMS model (Fleming and Brauer, 2018) according to the objectives of the present study jointly with findings provided by scientific studies performed in other catchments with similar features (Candela et al, 2012;Azmat et al, 2018;Ferreira et al, 2020;Đukic and Erić, 2021;Chen et al, 2021). Thus, the selected parameter set was composed by: i) the curve number (CN); ii) initial abstraction; iii) lag time recession constant; iv) ratio to peak; v) canopy maximum storage; vi) crop coefficient; vii) soil storage; viii) soil percolation; and, ix) groundwater 1 and 2 percolation rates.…”

“…Among different approaches, GIS-based hydrological modeling systems are becoming increasingly relevant tools because of their ability to handle spatial variations at the basin scale with a huge number of physiographic inputs (Nguyen et al, 2020;Senent-Aparicio et al, 2020;Jodar-Abellan et al, 2018). Several models have been developed such as SWAT (Arnold et al, 1998;Arnold et al, 2012), MODFLOW (Mcdonald and Harbaugh, 1984) or HEC-RAS (Brunner and Bonner, 1994;Ferreira et al, 2020). Most of them are integrated into a GIS framework and have demonstrated efficiently the ability to import spatiotemporal attributes.…”

Comparing the Hydrological Response of Forested Headwaters (Unregulated and Regulated with Check Dams) under Mediterranean Semi-Arid Conditions

“…However, the conditions of these catchments are significantly different from the three headwaters of our study, and this justifies the differences. Many other studies about HEC HMS applications report a range of 60-70 for CNs in catchments with different conditions [75][76][77].…”

Flood Mitigation in Mediterranean Coastal Regions: Problems, Solutions, and Stakeholder Involvement

“…Different types of floods have affected many regions worldwide, but within Europe, flash floods, river and lake flooding, cold-season floods and coastal floods are among the most common ones [2]. Due to the magnitude of societal impacts, several studies have been investigating different types and aspects of floods, such as the associated hydrological and hydraulic aspects [3], the environmental and societal consequences [4], and technical solutions to mitigate the problem [5]. Coastal floods, however, have been relatively less investigated comparing with other types of floods [6].…”