Towards an increase of flash flood geomorphic effects due to gravel mining and ground subsidence in Nogalte stream (Murcia, SE Spain)

Abstract

Abstract. Transition from endorheic alluvial fan environments to well-channelized fluvial systems in natural conditions may occur in response to base-level fluctuations. However, human-induced changes in semi-arid regions can also be responsible for similar unforeseen modifications. Our results confirm that in-channel gravel mining and aquifer overexploitation over the last 50 years in the case study area have changed the natural stability of the Nogalte stream and, as a result, its geomorphic parameters including channel depth and longitudinal profile have begun to adapt to the new situation. Using interferometric synthetic aperture radar (InSAR) data we obtain maximum values for ground subsidence in the Upper Guadalentín Basin of ∼ 10 cm yr −1 for the period 2003-2010. In this context of a lowered base level, the river is changing its natural flood model to a more powerful one. A comparison of the 1973 flood event, the most dramatic flood event ever recorded in the area, with the 2012 event, where there was a similar discharge but a sediment load deficit, reveals greater changes and a new flooding pattern and extension. In-channel gravel mining may be responsible for significant local changes in channel incision and profile. This, together with the collateral effects of aquifer overexploitation, can favour increased river velocity and stream power, which intensify the consequences of the flooding. The results obtained here clearly demonstrate an existing transition from the former alluvial pattern to a confined fluvial trend, which may become more pronounced in the future due to the time lag between the drop in aquifer level and ground subsidence, and introduce a new scenario to be taken into consideration in future natural hazard planning in this area.

Impacts of riverine sand mining on freshwater ecosystems: A review of the scientific evidence and guidance for future research

“…The degree of channel incision ranged considerably, from 0.5 to 3.5 m (Dang, Umeda, & Yuhi, ), up to 10 m (Calle, Alho, & Benito, ; Skalski et al, ; Moretto et al, ; Gumiero, Rinaldi, Belletti, Lenzi, & Puppi, ) to over 30 m in the Bachang River in Taiwan (Huang, Liao, Pan, & Cheng, ). Substantial channel incision was generally associated with channel narrowing linked to bank erosion due to over steepening and destabilization of banks (Ortega‐Becerril, Garzón, Béjar‐Pizarro, & Martínez‐Díaz, ; Campana et al, ). The extreme case of 30 m incision was accompanied by the channel narrowing to 1/6 of its original width.…”

“…Reduction in the water table level may also impact off‐channel wetlands and tributaries and alter the seasonal flow regimes of rivers (Neal, ). Groundwater abstraction and associated ground subsidence combined with sand mining was identified as a driver of channel incision in the Nogalte stream, southeast Spain (Ortega‐Becerril et al, ). Increased salt water intrusion was also a response to channel incision, with increased intrusion reported in the Kaluganga estuary in Sri Lanka (Ratnayake, Silva, & Kumara, ), the Tweed River in Australia (Rinaldi, Wyżga, & Surian, ), and in the Mekong (Brunier et al, ).…”

Development of a Proof-of-Concept A-DInSAR-Based Monitoring Service for Land Subsidence

“…In the view of an operational monitoring service for land subsidence especially in flood prone areas considering concomitant phenomena could be crucial for multi-hazard risk assessment to provide valuable insight for emergency management, civil protection activities, and land use management. Additionally, in the literature, it seems that hydraulic risk can be altered or even intensified by the land subsidence [77] changing the spatial The linear regression model built between EGMS and CSK data estimated an R-squared value of 0.82 (p-value < 2.2 × 10 −16 ). The results show that there are less than ten points with differences between EGMS-CSK LOS velocity higher than 5 mm/year (Figure 10b).…”

“…In the view of an operational monitoring service for land subsidence especially in flood prone areas considering concomitant phenomena could be crucial for multi-hazard risk assessment to provide valuable insight for emergency management, civil protection activities, and land use management. Additionally, in the literature, it seems that hydraulic risk can be altered or even intensified by the land subsidence [77] changing the spatial patterns of the hydraulic risk by modifying the inundation intensity (i.e., extent and spatial distribution of flooded areas) and consequently the spatial distribution of hydrodynamic variables (i.e., water depth and velocity) [78], and the correlation between the two phenomena is strictly associated with the study area setting [79]. A qualitative analysis related to the obtained results has been performed to evaluate the role of land subsidence in altering directly (i.e., changing the current topography) the hydraulic risk.…”

Overview of surface water hazards in China coalmines

“…They have also discussed the coupling relationship between ground fissures and mining fissures, leading to a sound evaluation of flooding risks in fully-mechanized caving mining of thick coal seams under surface water. In recent years, GPS and GIS techniques have been widely used to evaluate the characteristics of landforms, vegetation, surface erosion and surface water distribution in mining districts, and to study the ground subsidence and ground fissures caused by coal mining (Muntean et al 2016;Ortega-Becerril et al 2016;Zhang et al 2016). Additionally, previous researches on features of water sources and evolution of inrush conduits (Chen et al 2014;Polak et al 2016;Mostafa & Dieter 2017), both triggers to surface water hazards, have provided valuable reference for treating such hazards in coalmines.…”