Natural bank stabilization and riparian buffer galleries along the Odelouca River, Portugal

National Id
Site name
Odelouca River Basin (sub-catchment of the Arade River Basin)
The Odelouca River: Natural bank stabilization and riparian buffer galleries as part of mitigation and compensatory measures and through the use of bio-engineering techniques.
This project carried out in the Odelouca River (sub-catchment of the Arade River Basin, Algarve Region, South of Portugal) entailed the implementation of measures focused on the use of bio-engineering or natural techniques for rehabilitation of riparian buffer zones and river banks (such as river banks resectioning and placement of geotextile; live crib walls and vegetated gabions/rock armour construction and placement; planting of rehabilitated banks with native plant species; construction of artificial islands in the river channel, and clearance of invasive riparian plant species).
The in-depth description of the case study
RBD code
Data provider
Gonzalo Delacámara and Estefanía Ibáñez (IMDEA Water) in close cooperation with Samantha J. Hughes (UTAD, Portugal).
NWRM(s) implemented in the case study
Climate zone
warm temperate dry
Mean rainfall
Mean rainfall unit
Average temperature
Case Study Info
Light or indepth?
Average slope range
Monitoring impacts effects
Administrative annual costs
Administrative annual cost information
Performance impact estimation method
Edge of Field/Plot
Performance impact estimation information
For the sampling programme of 2012, the WFD compliant protocols were used: Biological Quality Elements (BQE), and physicochemical and hydromorphological support elements. Additional protocols to assess the quality of riparian habitat (and habitat quality in general) were used along the 7km stretch. The findings were compared with defined control sites located upstream the reservoir, which were considered as spots with a "more natural" riverine condition.
Application scale
Installation date
Performance timescale
11 - 20 years
High variability in rainfall patterns and risk of exposure to long drought periods may jeopardize the development of the riparian forest.
Besides, socio-economic aspects are relevant, as the alteration of the ecosystem is closely related to the economic activities being developed in the basin; in this specific context, irrigated agriculture.
Design contractual arrangement
Arrangement type Responsibility Role Comments Name
Design consultation activity
Activity stage Key issues Name Comments
Design land use change
Land use change type
Design authority
Authority type Role Responsibility Name Comments
Initiation of the measure
Agência Portuguesa do Ambiente
The national authority responsible of environmental issues. It was the programme promoter.
íguas do Algarve
> Type: íguas do Algarve is a private company
> Role: also Monitoring and rehabilitation programme
Determination of design details of the measure
University of Trás-os-Montes e Alto Douro (UTAD) [CITAB and Fluvial Ecology Lab]
> Type: UTAD is a research institution
> It was in charge of the design of the measure and also is responsible for the monitoring activities.
Regional / sub-national water authority
RICOVER Project (partners linked with Portugal case studies: íguas do Algarve, SA; Administração da Região Hidrográfica do Algarve)
> Type: Private company and water authority
> It was in charge of developing studies and also for the monitoring activities.
Determination of design details of the measure
Instituto Superior de Agronomia (ISA, University of Lisbon)
> Type: research institution
Private property owners
Their agreement was needed in order to proceed with the works linked to their lands.
Key lessons
- Artificial water retention measures (i.e. dam) do induce significant hydromorphological pressures on streams, thus hindering, among other things, natural water retention capacity downstream.
- Forested riparian zones deliver a number of ecosystem functions and services such as storing and fixing carbon; serving as wildlife habitats and ecological corridors; stabilizing riverbanks; providing shade, organic matter, and food for streams and their biota; retaining sediments and filtering chemicals (fertilizers and pesticides). Therefore, further to their effect on water yield, they contribute to a wide range of benefits for society.
- Riparian afforestation is by no means just about planting trees but also about introducing other vegetation types such as scrub, mostly through laterally recovering space for the river. Afforestation is compatible (and there are synergies indeed) with riparian clearing (in this case of invasive species).
- Although there is still no evidence available for the Odelouca sub-catchment, it all suggests that nitrogen levels can be reduced in rivers (by plants or microbial denitrification) through forcing water to circulate through afforested riparian buffers.
- The Odelouca case study is a good example about the characterization and assessment of intermittent Mediterranean river systems for restoration and requalification measures, including bioengineering techniques, closely related to green infrastructures.
- Monitoring is critical. River Habitat Survey (RHS) is a good way of assessing habitat quality including riparian complexity, diversity of hydromorphological features and artificialisation of aquatic habitats (features that may affect facets of the local water cycle).
- Riparian vegetation is central to the physical, chemical, and trophic health of streams. However, riparian restoration is still its formative stage and can be a complex process.
- Further efforts on the ex-post assessment of the impacts of vegetation changes on seasonal water yield and flow regime would be required.
Success factor(s)
Success factor type Success factor role Comments
Successful coordination between authorities
main factor

Cooperation between Aguas do Algarve, the promoter company of the Odelouca dam, and the rest of stakeholders enables the implementation of the measures relevant for the restoration of damage sections of the river.

Attitude of relevant stakeholders
main factor

Despite the already mentioned initial resistence, the initiative managed to get most of the needed permissions from landowners in order to start the works. 25 landowners accepted. Out of 32 identified private plots, 22 agreed to participate

Legal obligations
main factor
Communication activities
secondary factor
Existing staff and consultant knowledge
Financing type Comments
National funds
Main initial funding source was the Instituto Nacional de Agua (INAG), currently Âgencia Portuguesa do Ambiente (APA). (5,430,664 €)
EU-funds: Cohesion and regional development funds
Additional funding: SUDOE Interreg IV4b (Programme of Territorial Cooperation, via EU ERDF) (267,636 €).
Private funds
Aguas do Algarve, SA. (15,902 €)
Barrier type Barrier role Comments
main barrier
Physical constraints: Native species planted in the winter of 2011 were exposed to a considerable water stress due to a exceptionally dry spring and summer, which presented a real threat to their survival during the 1st year.
Attitude of relevant stakeholders
secondary barrier
- Local farmers and landowners (and residents) initially met the implementation of the characterisation programme and subsequent rehabilitation programme along the riverbanks with much suspicion and some resistance.
- Local farmers´ general perception was that land subject to intervention was being taken away from them, that risk of flooding would be increased, that the native plants planted along the intervention zones were of no commercial value and should be replaced (i.e by fruit trees), that project personnel were "trespassing" [although, according to Decreto-Lei 54/2005 (República, 2005), the river banks and the channel are part of the public domain].
- However, access has never been refused
Driver type Driver role Comments
Legal obligations
main driver
Financing share
Financing share type Share Comments
Policy description
In Mediterranean rivers, main human impacts over the last century have been mainly related to changes in land use and alterations in water and channel management (Hooke, 2006; Aguiar and Ferreira, 2005). The construction of the Odelouca Dam (2010), to increase water supply for the Algarve Region (southern Portugal), implied a major morphological alteration in the middle course of the river Odelouca. Prior to the construction of the dam, upstream and downstream sections of the river had been already modified by human activities (due to agriculture of extensive citrus groves replacing riparian forest), causing disturbance in riverbanks and riparian vegetation. The lower course is the most degraded stretch subject to re-sectioning and canalization in some areas. In many places invasive reed and giant reed beds have also replaced the riparian woody vegetation. The dam construction, and the flooded area, affected the section of the river with better ecologically preserved, which triggered the need of restoring the river functionality, water retention capacity of the system and the ecosystem function.

- WFD identified pressures: 4.2.3 and 4.2.4 Dams, barriers and locks for drinking water and for irrigation; 4.1.2. Physical alteration of channel/bed/riparian area/ shore of water bodie for agriculture
- The Habitat Directive specific pressures: A09: irrigation; A10: Restructuring agricultural land holding (removal of hedges and copses or scrub (A10.01), stone walls and embankments (A10.02); including (temporary) transition from dry to mesic or wet conditions due to irrigation); Diffuse pollution to surface waters due to agricultural and forestry activities (H01.05) and to household sewage and waste waters (H01.08); I01: invasive non-native species; J02.05.04: Modification of hydrographic functioning, general (reservoirs); J02.06.01: Surface water abstractions for agriculture; J03.01: Reduction or loss of specific habitat features; J03.02: Anthropogenic reduction of habitat connectivity
Policy target
Target purpose
Improved Biodiversity
Erosion Control
Policy pressure
Pressure directive Relevant pressure
Policy area
Policy area type Policy area focus Name Comments
Policy impact
Impact directive Relevant impact
Policy wider plan
Wider plan type Wider plan focus Name Comments
Policy requirement directive
Requirement directive Specification
Direct benefits information
- Improvement of water retention capacity in the system
- Reduction of flood vulnerability due to a better developed riparian forest
- Improvement of water quality

* The economic activity of the region is based on traditional activities, which occupied the riversides of the Odelouca with fruit trees (citrus) annual irrigation crops, vegetables gardens and livestock. Traditionally, landowners use as protection for flood risk ripraps and earth embankment, proving memory on past flood events (causing relevant damages). Despite the initial mistrust in the measures to be implemented, most landowners gave their permission to develop works within their property, which will have direct benefits on flood protection, improved soil composition, water availability, and landscape improvement.
Ancillary benefits information
- Water retention in riverbanks and improvements in infiltration capacity will provide better water security (reliability of supply and resilience to drought). Water provision to deliver water services to the economy, in particular to irrigated agriculture
- Flood security and protection (delay on flood peaks)
- Amenities (associated to habitat protection): fish and plants, tourism, recreation, and others
- Sediment retention
- Carbon fixation
- Wildlife habitats and ecological corridors
- Streambanks stabilization
- Providing shade, organic matter, food for streams and their biota
- Filtration of chemicals and other pollutants
Costs capital information
3,4 - 9,2 €/m2 (median: 4,5 €/m2): Cost range for geotextile application in similar projects carried out in Spain (Mediterranean basins)
20,7 €/m2: Cost of the application of geotextile (coco fibre) plus willow stakes in Spain.
Vegetated rock armour
72,3 €/m2: Live cribwalls (Krainer wall): 5 wood logs [h=2m; x=20cm] plus 30 willow (alive) stakes.
Vegetated gabions
3078 €/ha: Vegetation clearance (this is the average cost of 21 implemented projects in Spain). The range was 428 -7019 €/ha
25203 €/ha: Re-vegetation (this is the average cost of 21 implemented projects in Spain). The range was 1614 - 80249 €/ha
Costs maintenance information
The average annual maintenance cost for bioengineering measures (using alive material) is 5% of the investment cost. It is foreseen that maintenance should be 3 year long, thus the total maintenance cost could be estimated as the 15% of the investment cost
Costs total
Costs total information
This includes the total cost of the initial sub programme of measure (avifauna, fish fauna, riparian galleries and monitoring studies) (5,430,664 €) and the budget of the Project RICOVER for rehabilitation of riparian galleries (267,636 €).
Compensations scheme information
It is not specified in the literature of the case that the agreement with landowners required a compensation payment. Landowners had to give their consent to the implementation of the measures affecting their property/land.
Ecosystem improved biodiversity
Information on Ecosystem improved biodiversity
The Odelouca River is part of the Natura 2000 Network, as it is the habitat of two endemic fish species and the Iberian Lynx. By recovering the river functions, and retaining water, a proper functioning of ecosystems to support the habitat of these species is possible.
Ecosystem provisioning services
Ecosystem impact climate regulation
No information available
Information on runoff reduction
The restored cover of trees and bushes in the riparian gallery will intercept precipitation when it reaches a more mature structure, as currently, not enough time lapse has occurred to perceive these effects. Intercepted precipitation reduces direct runoff and delays the onset of peak flows, and it will become more efficient with a larger and more complex structure of the riparian gallery (i.e. width, different heights/layers of vegetation within the gallery). Some of the measures included the creation of artificial islands in the river channel, which may control the flow regime. Besides, the restoration of riverbanks and the elimination of invasive reed will reduce and diversify stream flow velocity.
Information on Peak flow rate reduction
See runoff attenuation above. However, the Odelouca is a regulated river now where the flow regime downstream is a managed environmental flow that is released from the Odelouca dam.
Information on Increased infiltration
A developed riparian forest increases the density of roots in the soil and creates coarse substrates. During periods of high-energy flow, plant debris and sediments are conveyed and deposited downstream as the flow decreases, increase habitat heterogeneity. A more heterogeneous structure of soils and riparian areas improve retention via infiltration of water from the river itself during peaks in flow and from precipitation.
Information on Soil moisture
A well-developed riparian gallery provides organic matter to the soil through falling leaves and decomposition of senescent plants, which contributes to the creation of natural mulch. The result is an increase of organic content of the soil, which enhances its moisture content and fertility. Other side benefits of a developed riparian forest are the increase of shade areas, lowering local surface and air temperatures, thereby reducing rates of evapotranspiration.
Information on Ecosystem flood control volume
Bank storage of water has been enhanced with the implemented measures and thus its important role in reducing flood intensity and sustaining stream flow decreases. Measures have effect on the slope, rugosity, complexity and state of the riverbank, which are important factors in water storage capacity and retention.
Information on Restoring hydraulic connections
The restoration of riverbanks improves lateral connectivity of the river (interaction of the river with the valley) and vertical interaction with groundwater.
Information on Water quality overall improvements
There is not measured evidence yet, but a well-developed riparian forest will also help retain pollutants (i.e excess nutrients from agriculture) by "defiltering" water as it moves to the groundwater helping to prevent contamination of aquifers.
Information on Soil quality overall soil improvements
Increase in organic matter in soil and the development of roots enhances its structure and improves its functionality.


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