Assessment of the geomorphic effectiveness of controlled floods in a braided river using a reduced-complexity numerical model

Abstract

Abstract. Most Alpine rivers have undergone significant alterations in flow and sediment regimes. These alterations have notable effects on river morphology and ecology. One option to mitigate such effects is flow regime management, specifically through the reintroduction of channel-forming discharges. The aim of this work is to assess the morphological changes induced in the Piave River (Italy) by two distinct controlled-flood strategies, the first characterized by a single artificial flood per year and the second by higher-magnitude but less frequent floods. This work involved applying a two-dimensional reduced-complexity morphodynamic model (CAESAR-LISFLOOD) to a 7 km long reach, characterized by a braided pattern and highly regulated discharges. Numerical modelling allowed the assessment of morphological changes for four long-term scenarios (2009–2034). The scenarios were defined considering the current flow regime and the natural regime, which was estimated by a stochastic physically based hydrologic model. Changes in channel morphology were assessed by measuring active-channel width and braiding intensity. A comparison of controlled-flood scenarios to a baseline scenario (i.e. no controlled floods) showed that artificial floods had little effect on channel morphology. More channel widening (13.5 %) resulted from the high-magnitude flood strategy than from the application of the other strategy (8.6 %). Negligible change was observed in terms of braiding intensity. The results indicate that controlled floods do not represent an effective solution for morphological recovery in braided rivers with strongly impacted flow and sediment regimes.

Flood Susceptibility Mapping Using Logistic Regression Analysis In Lam Khan Chu Watershed, Chaiyaphum Province, Thailand

“…The Piave River in Italy also found that the landscape of the basin was a braided river. It is similar to the floods in the Piave River in northern Italy, which appear braided rivers with strongly impacted flow and sediment regimes (Ziliani et al 2020). Like the results of a study by (Rajbanshi et al 2022) in the braided Brahmaputra River in Assam, India, it was found that the 2019 major floods in the Brahmaputra River affected sediment changes in the river, whether it is the movement or accumulation of sediments in the river.…”

LISFLOOD-FP 8.1: new GPU-accelerated solvers for faster fluvial/pluvial flood simulations

“…LISFLOOD-FP is a raster-based open-source hydrodynamic modelling framework that has been applied in many fields of earth sciences, including morphodynamic modelling (Coulthard et al, 2013;Ziliani et al, 2020), urban drainage modelling (Wu et al, 2018;Yang et al, 2022), population mapping (Zhu et al, 2020), coastal flooding (Hirai and Yasuda, 2018;Seenath, 2018), uncertainty quantification (Liu and Merwade, 2018;Beevers et al, 2020;Jafarzadegan et al, 2021;Karamouz and Mahani, 2021;Yin et al, 2022;Zeng et al, 2022) and coupled hydrological-hydraulic modelling (Siqueira et al, 2018;Towner et al, 2019;Rajib et al, 2020;Makungu and Hughes, 2021;Nandi and Reddy, 2022). It has undergone extensive developments and testing since its conception (e.g.…”

The impact of sediment flux and calibre on flood risk in the Kathmandu Valley, Nepal

“…For example, the CAESAR-Lisflood (C-L) model , the CAESAR LEM model (Coulthard et al, 2002) integrated with the Lisflood-FP 2D hydrodynamic model (Bates & De Roo, 2000;Bates et al, 2010), offers a choice of three approaches for calculating sediment transport: the Meyer-Peter and Müller (1948) empirical formula for moderate transport rates of gravel, the Einstein (1950) statistical method for sandy rivers and the Wilcock and Crowe (2003) empirical approach derived from mixed gravel and sand tests that gives accurate predictions of transient bed armouring aggradation and degradation. The CAESAR LEM or integrated CAESAR-Lisflood models both use a digital elevation model to define topography and have been applied to simulate land evolution scenarios for many parts of the world (Coulthard et al, 2002(Coulthard et al, , 2005Coulthard & Macklin, 2003Coulthard & Van De Wiel, 2013Feeney et al, 2020;Hancock, 2009;Liu & Coulthard, 2017;Ramirez et al, 2020Ramirez et al, , 2022Skinner & Coulthard, 2023;Skinner et al, 2018;Van De Wiel et al, 2007;Wong et al, 2021;Ziliani et al, 2020). Recently, Skinner et al (2018) carried out a sensitivity analysis of the C-L (v1.8f) model using 50 m and 10 m DEMs for the Swale catchment, UK (a temperate, perennial medium-sized catchment with an area of 181 km 2 ), and the Tin Camp Creek catchment, Australia (a tropical, ephemeral small catchment with an area of 0.5 km 2 ) considering bedload only (without using suspended sediment processes in the model).…”