Hidrología y Cambio Climático/

Hydrology and Climate Change


Extreme Floods in Small Mediterranean Catchments: Long-Term Response to Climate Variability and Change

-The influence of climate variability on flooding was evaluated by an analysis of a 500-year palaeoflood and documentary records at Montlleó River, eastern Spain.

- Five paleofloods exceeded 740–950 m3 s−1; vs. 129 m3s-1highest gauged flood s.1971.

- Flood occurred in cluster episodes (30-year duration) either during cooler than usual climate (about 0.3 °C and 0.2 °C), or during high climate variability (floods and droughts).

- Flood quantiles from palaeoflood data showed 30%–40% higher peak discharges than those using only instrumental records.

- These extended flood records can assist on low-regret actions for flood-risk adaptation.

Large ice-age megafloods have significantly altered Patagonian landscapes, acting as triggers of climate change.

We provide the first detailed reconstruction of catastrophic glacial lake outburst flooding (>110,000 m3s-1) from the Southern Hemisphere, focusing on the Río Baker catchment in central Patagonia.

Morphological changes and sediment connectivity evaluation during flooding using high resolution photogrametry

- We evaluate morphological changes, sediment tranfers and functional sediment connectivity caused by flood events.

- Quantification of morphological change and sediment budgets was provided by Photogrammetric flights.

- A sediment connectivity index is proposed.

Frequency of boulders transport during large floods in hyperarid areas using paleoflood analysis – An example from the Negev Desert, Israel

- The 2004 flood (470 m3 s−1) in the hyperarid, ungauged Nahal Hatzera ephemeral stream (45 km2), transported and deposited 0.85–2.1 m concrete boulders.

- A 600 years paleoflood record of 23 floods with peak discharges of 200–760 m3 s−1, indicates an average return period of 120 years for this event. 

-The shear stress and stream power indicate that the moderate-large floods are the most geomorphically effective floods rather than the largest floods in Nahal Hatzera.

Flood hydro-geomorphology and vegetation dynamics along the hyperarid Kuiseb River, Namibia and detecting large floods in remote deserts

- The Kuiseb River flash floods  travel ~280 km downstream, before recharging the aquifers that sustain a 130-km long green belt across the hyperarid Namib desert.

-  This study reveals the importance of flood properties on the oasis life cycle and emphasizes the impact of drought and wet years.

- The downstream aquifers are fed only by the largest flood discharge that allows the infrequent germination of vegetation.

-Variations in NDVI index was revelead as an effective tool in determining occurrences of large floods in these headwater-fed hyperarid regions. 

Impacts of sediment connectivity on Holocene alluvial records across a Mediterranean basin (Guadalentín River, SE-Spain)

- Alluvial chronologies in two contiguous valleys show out-of-phase sedimentation periods under low connectivity conditions (9-3 ka), and in-phase cut-and-fill cycles after valley re-connection (post-3.0 ka).

- Vertically stacked alluvial sequences were dominant during periods of low connectivity.

whereas stair-case fill terraces due to cut-and-fill cycles occurred on connected reaches

- During the late Holocene alluvial activity periods coincide with morpho-stratigraphic data from the lower Guadalentín, indicating that fluvial connectivity throughout the catchment was only completed in the late Holocene.