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

Abstract

This study has evaluated the runoff and erosion rates in torrents of Southern Italy, two forested headwaters with very similar climatic, hydrological and geomorphological characteristics; in one headwater, 15 check dams were installed in the mid-1950s, while the other is not regulated with engineering works. To this aim, the hydrological variables have been modeled over 15 years after check dam installation using the HEC-HMS (Hydrologic Engineering Center-Hydrologic Modeling System) model coupled to the MUSLE (Modified Universal Soil Loss Equation) equation. The model simulations have shown that check dams have not played a significant role in reducing the surface runoff compared to the unregulated torrent; in both catchments, the well-developed forest cover determined very low runoff coefficients (lower than 0.3%) with a scarce runoff generation capacity. Additionally, the reduction in peak flow due to the check dams was not significant, on average −7.4% compared to the unregulated headwater. Check dams have retained sediments for about 8–10 years after their installation, reducing erosion by about 35%, although soil loss was much lower than the tolerance limit in both catchments. After the sediment retention capacity of the dam sediment wedge was depleted, the sediment yield in the regulated torrent was even higher (by about 20%) compared to the unregulated catchment. Overall, the study has shown that the use of check dams as a catchment management strategy of forested headwaters under semi-arid Mediterranean conditions should be considered with caution, since the structures could be ineffective to reduce water and sediment flows during floods or, in some cases, check dams may increase erosion rates.

Short-term changes in soil properties after prescribed fire and mulching with fern in Mediterranean forests

“…One of the most detrimental effects of prescribed fire is the possible increase in runoff and erosion in the short term (Lucas-Borja et al 2019), due to vegetation removal and sudden changes in the properties of soils (Cawson et al 2012;Alcañiz et al 2018). This is an important concern when risk of wildfire endangers forests on steep slopes with highly erodible soils, such as in many environments of Southern Europe (e.g., Fortugno et al (2017); Bombino et al (2021b) in Southern Italy). To the authors' best knowledge, so far no studies have evaluated the soil changes after prescribed fire in these environments, where the wildfire and erosion risks are high, due to climatic and geomorphological characteristics.…”

Hydrometeorological analysis of a flash flood event in an ungauged Mediterranean watershed under an operational forecasting and monitoring context

“…This approach was originally developed by the United States Department of Agriculture, Soil Conservation Service (today known as Natural Resources Conservation Service [NRCS]), to predict direct runoff volumes for given rainfall events and primarily for the evaluation of storm runoff. SCS‐CN has been widely applied in ungauged Mediterranean watersheds (Bombino et al, 2021; Lucas‐Borja et al, 2020; Papaioannou et al, 2018; Petrović et al, 2021; Psomiadis et al, 2020; Zema et al, 2017). The HEC‐HMS software (HEC‐HMS, 2016) was used to implement the SCS‐CN model and estimate the flood hydrographs using different rainfall datasets.…”

Simulation of Accelerated Subcritical Flow Profiles in an Open Channel with Emergent Rigid Vegetation

“…Vegetation has an important hydrological role at the basin scale because it reduces erosion and floods and increases infiltration [1][2][3][4][5]. On the other hand, vegetation along watercourses plays an important role in the river ecosystem, enhancing the landscape.…”