Case study:Experimental flood in the Pisuerga river
To discuss or comment on this case study, please use the discussion page.
- 1 Project overview
- 2 Image gallery
- 3 Catchment and subcatchment
- 4 Site
- 5 Project background
- 6 Reasons for river restoration
- 7 Measures
- 8 Monitoring
- 9 Additional documents and videos
- 10 Additional links and references
- 11 Supplementary Information
|Project web site|
|Themes||Environmental flows and water resources, Habitat and biodiversity, Hydromorphology|
|Main contact forename||Fernando|
|Main contact surname||Magdaleno|
|Main contact user ID|
|Contact organisation web site|
|Parent multi-site project|
| This is a parent project
encompassing the following
The release of the experimental flood was performed in May 2014 in order to improve river processes downstream of the dam (the Requejada Dam), and to increase geomorphic and ecologic dynamics—nowadays impoverished by dam operation. The release was conducted under a number of constraints: (i.) ensuring the security of people and property (the flooding protocol had to be activated in the river); (ii.) accommodating an existing fishing preserve (Quintanaluengos), whose managers requested a specific day of the week for the discharge; (iii.) the hydraulic characteristics of the open-channel spillways in the dam (bottomwithdrawal was not used during the discharge).
The flood was approximately calculated to fill the ordinary channel, with a peak discharge of 96 m3 /s (associated with a recurrence interval of 2.4 years), duration of 10.5 h, and total volume of 0.82 hm3 . The ramping rates were adjusted via logistic functions, and modified in the hydrograph every 10 min (Fig. 2). In some river sections, the flow slightly overtopped the bank and created minor flooding in adjacent fields.
Monitoring surveys and results
Analyses of the ecomorphological effects of the controlled flood were based on monitored changes in river morphology, suspended load transport, and bedload transport. River morphology was analysed in terms of variation in the geometry of two channel sections (one in a riffle, one in a pool) along the study sub-reach, variation in the granulometric composition in those two sections, and assessments of the refuge index for fishes (García de Jalón et al., 1993) and the river habitat index (IHF – Pardo et al., 2002). Suspended load was measured in 10 different water samples. Bedload transport was analysed in four different locations by measuring the size of pre-coloured coarse sediments over 1 × 1 m2 , and their relative motion along the channel (Leopold, 2006).
Monitoring showed that changes in the river micro- and mesohabitats were highly limited (Cebrián et al., 2015) (Table 1). The variables analysed were only slightly modified and the values of habitat indices were consistent with pre-flooding conditions. The value of the suspended load transport was low and in direct response to flow changes, which could indicate that the origin of the suspended sediments was in the channel downstream of the dam. For bedload transport, most removed particles were smaller than 64 mm and were concentrated in the pool area, likely due to the high increment of water velocity. Larger particles were occasionally removed or flipped.
Thus, the experimental flood release showed limited geomorphic benefit, despite reaching (or even overtopping) the channel banks. Most changes were related to the transport of fine sediments, but they did not enhance habitat variation, or create new fluvial forms. Cebrián et al. (2015) suggested that the results may have been associated with extensive modification of the channel after six decades of dam management. Bed incision or unbalanced river morphology could be hampering the geomorphic influence of ordinary flows, requiring higher flows than theorised to enhance sound morphological and ecological changes.
Catchment and subcatchment
Cost for project phases
Reasons for river restoration
Hydromorphological quality elements
Biological quality elements
Physico-chemical quality elements
Additional documents and videos
Cebrián, M., Minaya, R., Prieto, L., Rodríguez, J., Rodríguez, I., 2015. Primer ensayo de evaluación de caudal generador en la cuenca del Duero aguas abajo de la presa de Requejada (río Pisuerga, Palencia). In: Actas del II Congreso Ibérico de Restauración de Ríos (Restauraríos). Pamplona. pp. 54–64.
García de Jalón, D., Casado, C., Mayo, M., Gallego, B., García, J., Brotons, P., Hervella, F., Mingo, A., 1993. Fijación de caudales mínimos ecológicos para los ríos Esla, Pisuerga, Duero y Duratón. C.G.S. S.A.
Leopold, L.B., 2006. A View of the River. Harvard University Press, Cambridge Massachusetts (298 p.).
Pardo, I., Álvarez, M., Casas, J., Moreno, J.L., Vivas, S., Bonada, N., Alba-Tercedor, J., Jáimez-Cuéllar, P., Moyà, G., Prat, N., Robles, S., Suárez, M.L., Toro, M., VidalAbarca, M.R., 2002. El hábitat de los ríos mediterráneos: Diseño de un índice de diversidad de hábitat. Limnetica 21 (3-4), 115–133.
For more references, please check the link to the article above.