Natural Water Retention Measures

Hobølelva River: erosion, landslide & eutrophication

admin — Sat, 20 Mar 2021 06:37:53 +0000

Hobølelva River: erosion, landslide & eutrophication admin Sat, 03/20/2021 - 07:37

National Id

Policy description

Local involvement has been extensive since around 1990 as catchment has been used as a study site in many projects, e.g., EU FP7 Refresh, EuroHarp, H2020 Recare). NIBIO has arranged many workshops with stakeholders of this catchment:
- Farmers and land owners;
- Water boards: local (for the catchment) and regional (for the river basin of Glomma);
- Municipalities;
- Boaters, canoes (mainly in the lake), local communities;
- Drinking water supply company (MOVAR);
- Environmentalists (f.ex., SABIMA);
- Hunting and fishing associations;
- Tourist association (Turistforeningen);etc.

Photo gallery

Eutrophication – severe algae blooms around 2004-2007. Agriculture being main source of phosphorus in fresh water

Riverbank erosion – additional P source; river flows through marine clay deposits, naturally rich in apatite – a phosphorus-rich mineral.

Floods of varying magnitude occur frequently, typically during snow melt and autumn rainstorms.

Monitoring impacts effects

Site name

Hobølelva River

Summary

The Kråkstadelva catchment, as case study area, is located within the Hobølelva watershed, located ca. 30km S-SE of Oslo, Norway. The area of the Kråkstadelva catchment is approximately 51 km2. Agricultural land covers ca. 43% of the catchment (22km2) and it is dominated by cereal production. Forest covers ca. 45% of the catchment. Heavy clay soils dominate in the area (up to 80% of clay content). Mean annual temperature is 5.3°C and average annual precipitation is c.a. 864 mm. Floods of varied magnitude occur frequently in the catchment, typically during spring snow melt and autumn rainstorms. The main challenge in the area is water quality (incl. high phosphorus pollution) and soil erosion (incl. riverbank erosion and quick-clay landslides). There is already high focus on environmental mitigation measures, for example reduced tillage (no tillage in autumn), buffer zones, grass-covered water ways, constructed wetlands and the use of catch-crops.

OPTAIN project will support the case study team in identifying new land management strategies, including the best combination and allocation of measures in the catchment as well as implementing new (combinations of) measures, in order to improve water retention in the soil and the landscape and as a result reduce the risk of flooding, and improve water quality downstream.

The in-depth description of the case study

10_Hobol_NIBIO.pdf

Climate zone

cool temperate moist

Mean annual rainfall

600 - 900 mm

Part of wider plan

RBD code

NO011

Financing mechanism

Mean rainfall

Annual precip. (1993-2004): 651-1305 mm.yr-1(avg. 864 mm.yr -1)

Policy target

Target purpose
Erosion Control	View
Peak-flow reduction	View
Pollutants Removal	View

Mean rainfall unit

mm/hour

Policy pressure

Pressure directive	Relevant pressure
		View

Average temperature

Mean temp.: 5.3°C (annual), -4.8°C (Jan/Feb), 16.1°C (July).

Policy area

Policy area type	Policy area focus	Name	Comments
				View

Transboundary

Data provider

Nibio

Policy impact

Impact directive	Relevant impact
		View

Policy wider plan

Wider plan type	Wider plan focus	Name	Comments
				View

Mean runoff

4.7 m3.s

NWRM(s) implemented in the case study

Sediment capture ponds

Stream bed re-naturalization

Low till agriculture

Buffer strips and hedges

Policy requirement directive

Requirement directive	Specification
		View

Optain's measures

Small retention ponds in the forest

Grass or stubble in areas prone to flooding and erosion

Grass buffer zones alongside waterways in cropland

Grassed waterways

Success factor(s)

Success factor type	Success factor role	Comments
			View

Financing

Financing type	Comments
		View

Barrier

Barrier type	Barrier role	Comments
			View

Driver

Driver type	Driver role	Comments
			View

Remarks runoff imperviousness

Avg. water discharge: ca. 4.7 m3.s (max: 102 m 3.s).

Financing share

Financing share type	Share	Comments
			View

Type

Case Study Info

Light or indepth?

In-depth

Average slope range

Elevation range: 25 - 346 m a.s.l.

Vegetation class

In the North: mainly forested with Pre-Cambrian bedrock. The land use is 79% forest, 16% agriculture and 5% water areas.

Public consultation

Contractural arrangements

Design contractual arrangement

Arrangement type	Responsibility	Role	Comments	Name
					View

Design consultation activity

Activity stage	Key issues	Name	Comments
				View

Design land use change

Land use change type
	View

Design authority

Authority type	Role	Responsibility	Name	Comments
					View

New French case studies

admin — Wed, 29 Apr 2020 13:59:46 +0000

New French case studies admin Wed, 04/29/2020 - 15:59

Erosion control by agricultural and forestry techniques and soft hydraulics in the Bas-Rhin

admin — Wed, 19 Feb 2020 16:29:03 +0000

Erosion control by agricultural and forestry techniques and soft hydraulics in the Bas-Rhin admin Wed, 02/19/2020 - 17:29

National Id

France_12

Policy description

The Bas Rhin department is regularly subject to muddy water flows. These occur during Spring and summer storms on silty hills with Spring crops (beets, corn, etc.).
Silt mobilized by rainfall on bare plots is carried downstream, where there are sensitive issues such as villages in the valleys (Figure 1). Mudflows impact both the receiving area (villages and local residents) and the emitting area (loss of soil for farmers).
Several factors have led to an increase in the risk of this phenomenon occurring since the 1950s:
Climate changes favouring heavier rains earlier in the season.
The decrease in grassland (-44% cattle between 1979 and 2000) and the increase in agricultural areas with little coverage during Spring and early summer.
Theimplementation of land consolidation actions leading to an extension of the field size and the removal of landscape elements (hedges, rural roads, embankments, etc.).
Urbanisation is also accompanied by the artificialisation of soils (+1047 ha/year between 1984 and 2000) and the progressive removal of buffer zones such as orchards and meadows.
As a result, the frequency of muddy water flows has increased, and they occur earlier and earlier in the season.

Project scale

Large

Photo gallery

Fascine recently implemented in the frame of the project, SDEA

Project scale specification

The policy was conducetd over a long period in the region.

Summary

The Bas Rhin department is sensitive to muddy water flows occuring during Spring and early summer storms, which impact farmers and villages located downstream of agricultural plots. In order to reduce this risk, the Agriculture Chamber and the local authorities are working together to develop ways of combating these phenomena, which are harmful to downstream areas. Within this partnership framework, a diagnosis of the erosion and mudslides risks is carried out by the Alsace Agriculture Chamber at the commune level, and gives rise to proposals for concerted crop rotation (preventive measures) and soft hydraulic developments (curative measures). On the basis of these recommendations, the installation of hedges, weirs and grass strips is carried out by different project leaders depending on the territory (municipalities or intercommunal). Concerted crop rotation is coordinated by the Agriculture Chamber, and also allows for the gradual transition of some crops to no-till techniques, while the communities manage the implementation of soft hydraulic works.

Application scale

Region

Reviewed by

Fribourg-blanc

The in-depth description of the case study

mnre_rex06_plaine_dalsace.pdf

Installation date

2008

Remarks

The project covers a wide area, with several hundred towns and villages.

Location description

The Bas-Rhin department is located in the North-East of France. The Rhine plain land-use is mostly dedicated to Spring crops with no landcover during winter. Crops are located on the top of the hills and on the slope, while villages lie in the lower land.

Age

NUTS Code

Alsace

Key lessons

The combination of preventive measures (crop rotation, no-tillage cultivation) and curative measures have reduced the risk of mudflow.

RBD code

FRC

Policy target

Target purpose

Policy pressure

Pressure directive	Relevant pressure

Policy area

Policy area type	Policy area focus	Name	Comments

Transboundary

Policy impact

Impact directive	Relevant impact

Policy wider plan

Wider plan type	Wider plan focus	Name	Comments

NWRM(s) implemented in the case study

Buffer strips and hedges

Policy requirement directive

Requirement directive	Specification

Longitude

7.686808

Latitude

48.682818

Success factor(s)

Success factor type	Success factor role	Comments
Attitude of relevant stakeholders	main factor	The recurrence of mudslides in the department and the impacts on the inhabitants and the search for solutions to the problems faced by local residents. The work done by the Agriculture chamber as a result of the departmental regrouping facilitated the choice and the location of development measures. The multiplicity of actors involved in this departmental approach is important: communes, metropolis, unions, agriculture chamber, farmers, researchers, etc. The project managers note a positive development of the acceptance of soft hydraulics measures by the agricultural profession over the last ten years. In the short term, these works are also cheaper alternative measures compared to the implementation of conventional retention basins (but In the long term, the costs of compensation and maintenance are important).	View

Financing

Financing type	Comments

Barrier

Barrier type	Barrier role	Comments

Driver

Driver type	Driver role	Comments

Financing share

Financing share type	Share	Comments

Light or indepth?

In-depth

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

Information on runoff reduction

The effectiveness of soft-hydraulic measures has been demonstrated by modelling of watersheds concerned with muddy casting phenomena. The visual observation of the various carriers of project confirms the retention of sediments by the soft hydraulic developments. The co-benefits of this work are landscape improvement, restoration of habitat for small wildlife, and softening of tensions between farmers and inhabitants of villages that have been impacted by past muddy water flows. The measures are also considered less expensive in the short term than the construction of mud ponds.

Reconstruction of the hedgerow on the Léguer basin

s.le-grumelec — Wed, 04 Dec 2019 13:46:03 +0000

Reconstruction of the hedgerow on the Léguer basin s.le-grumelec Wed, 12/04/2019 - 14:46

National Id

France_15

Performance impact estimation method

Catchment outlet

Policy description

The Léguer River is labelled a Wild River. Its catchment area is one of the most hedgerow territory in Brittany, with an average 150 meters of hedge per hectare. However, this hedgerow has been gradually eroded as a result of agricultural mechanization and land consolidation, as well as the phasing out of hedge and slope maintenance seen as a cost without any benefit. This decline was estimated at a loss of 3 linear meters per hectare per year.
The main objective of the project was to improve water quality and control erosion. Limiting runoff allows water to stay longer before reaching the watercourses, giving time to natural processes to occur to purify the water by soil microorganisms or light.
Secondly, the restoration of hedged land is of interest for biomass supply, biodiversity conservation, carbon sequestration, renewable wood production, for the wind-breaking role of hedges, livestock protection and landscape restoration.

Project scale

Large

Photo gallery

Planting hedgerow in the Léguer basin, BVVL

Performance impact estimation information

A pre-configuration study was conducted to assess the effect of hedgerow restoration and practice changes on water quality.

Project scale specification

The project is covering the entire Léguer river basin and specific research were conducted on sub-catchments.

Summary

The Léguer River catchment is one of the most hedged areas in Brittany. However, this territory has suffered a decline in its hedgerow mesh as a result of agricultural mechanization and land consolidation operations. Faced with the degradation of the Leguer's water quality observed in the 1990s, elected officials in the Leguer's watershed became aware of the need to preserve the hedgerow to stop this degradation, and to consider its restoration to improve water quality. Since 1999, the Leguer's watershed committee undertook awareness-raising of the watershed population, before experimenting with the restoration of hedges and embankments in several pilot basins. This work was then extended to the entire watershed, leading to the restoration of 300 kilometers of hedges and embankments. This action is still ongoing today, and aims in particular to ensure the sustainability of existing linear thanks to urban planning tools and the promotion of hedged farmland.

Application scale

River Basin

The in-depth description of the case study

mnre_rex04_bassin_versant_du_leguer.pdf

Installation date

1999-2019

Location description

The Leguer is a coastal river of the Côtes d'Armor that flows into the Bay of Lannion, and whose basin has a historically dense hedgerow mesh. Hedges and embankments are distributed heterogeneously throughout the watershed and are threatened in several sectors by changes in maintenance practices and the gradual disappearance of certain linear areas.
In Bretagne, 80% of drinking water comes from surface water pumping, which makes this resource fragile and sensitive to diffuse or point pollution. Several water intake points were closed in the mid-1990s due to significant water quality degradation. Due to the positive influence that hedgerow can have on the quality of surface water, policies for the preservation and restoration of hedgerow have emerged in BrIttany.

NUTS Code

Bretagne

Key lessons

The area was primarily the subject of consolidation actions to increase size of fields by agriculture authorities. This led to an important destruction of hedgerows and some farmers were therefore reluctant to replant hedges shortly after. The fact a wood energy sector using wooden chips elaborated using recovered wood from the maintenance of hedges has helped convince local stakeholders to engage at such a large scale. Almost 300km of hedgerows and embankments have been restored in the basin. A reduction of chemical and nutrient pollution has been found. the research conducted showed the habitat role of hedgerows for agriculture auxilaries, made possible in oparticular with a diverse and good stratified hedge. The project has created a common dynamic towards preservation and restoration of hedges and embankment beyond farmers, including citizen and elected officials and created a territorial identity. The project leader underline is important to watch not only the increase of the hedgerows but also their maintenance.

RBD code

FRG-La Loire, les cours d'eau côtiers vendéens et bretons

Monitoring parameters

The project does not implement monitoring of the flow and water level of the Leguer.
Study of a pilot sub-basin
In the 2000s, the Comité du Bassin Versant du Léguer (CBVL) conducted a study of the Kervulu watershed (pilot basin) to assess the effect of hedgerow restoration and changes in practices on water quality.
Physico-chemical and chemical monitoring
A water quality monitoring network on pesticide parameters has been implemented since 2007, in addition to the existing monitoring network (WFD network).
Biodiversity monitoring
The Leguer hedgerow project, led by INRA (UMR BAGAP), aims to evaluate the role of the hedge as a shelter for auxiliary fauna, both through the in situ assessment of hedge biodiversity at the hedge and farm levels, and through the analysis of the ecological connectivity of the landscape and the establishment of ecological networks in planning documents.

Policy target

Target purpose

Policy pressure

Pressure directive	Relevant pressure

Area (ha)

50 000 ha

Policy area

Policy area type	Policy area focus	Name	Comments

Transboundary

Area specifications

300 km of planted or restored hedges and embankement

Policy impact

Impact directive	Relevant impact

Policy wider plan

Wider plan type	Wider plan focus	Name	Comments
Regional	Environment & Biodiversity	"Breizh bocage"	The programme aims at the Brittany region level to enhance protection and restoration of hedgerow landscapes.	View

Source(s)

Rapport de présentation, état initial de l’environnement

Retour d'expérience - Le programme Breizh Bocage au service de la restauration de l’eau

L’eau en Loire Bretagne, les trophées de l’eau en Loire Bretagne 2009

Le suivi de la qualité de l’eau

Bocage

Bocage et cultures : un mariage harmonieux sur le Kervulu

Le projet Léguer Bocage

NWRM(s) implemented in the case study

Buffer strips and hedges

Policy requirement directive

Requirement directive	Specification

Longitude

-3.3920

Latitude

48.5865

Success factor(s)

Success factor type	Success factor role	Comments
Financing possibilities	main factor	The emergence of the wood sector (grove wood, production of wood chips to supply boilers) has been a real opportunity for farmers to find an economic interest. The gradual structuring of an energy wood sector allowing the valorization of wood from the maintenance of hedges in the form of logs or wood chips has helped convince the territory actors commit themselves on such a scale. Finally, the project benefited from the regional dynamics linked to the Breizh Bocage scheme.	View

Financing

Financing type	Comments
Local funds		View

Barrier

Barrier type	Barrier role	Comments
Attitude of relevant stakeholders	secondary barrier	Some farmers were reluctant to plant hedgerow lines soon after participating in land consolidation actions.	View

Driver

Driver type	Driver role	Comments

Financing share

Financing share type	Share	Comments

Light or indepth?

In-depth

Favourable preconditions

The planting of hedges helps to fight against erosion and improve the quality of surface water. The many co-benefits of this measure have contributed to the progressive extension of the restoration program to the entire watershed.

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
Other	Initiation of the measure	Responsible	Lannion Trégor Communauté (LTC)	this is a mutli municipality administration, common organisation in France to gather resources to manage technical topics such as water, waste and other topics.	View
Local water authority	Initiation of the measure	Responsible	Comité bassin versant du Léguer (CBVL)		View

Hydrological effects

The hydrological response to rain event seems longer than river basins with no action on hedgerows. Farmers also report complete stop of mud flows in lower areas of the fileds which were previously common problem.

Information on Water quality overall improvements

The study carried out in the Kervulu basin showed that the sub-basins that had been the subject of restoration of the hedgerow coupled with the adoption of rationale weed control practices contributed less to pollution (in particular phosphorus and pesticides) of surface water than the other basins.
Since the 2000s, an improvement has been observed on the nitrate parameter, while it was increasing in the 1990s.

Information on Reducing flood risks, quantity

During floods, it was observed that the hydrological behaviour of the Leguer appeared less reactive than that of other nearby rivers that had not been the subject of such a restoration program.
In addition, farmers report that they have noticed the disappearance of mud flows on the lower part of their fields following the creation of hedges that break the slope.

Le projet Léguer Bocage

s.le-grumelec — Wed, 04 Dec 2019 13:45:50 +0000

Le projet Léguer Bocage

Year

consulted 02/12/2019

s.le-grumelec Wed, 12/04/2019 - 14:45

Authors

INRA

Case study(ies)

Reconstruction of the hedgerow on the Léguer basin

NWRM(s)

Buffer strips and hedges

Source type

Website

Bocage et cultures : un mariage harmonieux sur le Kervulu

s.le-grumelec — Wed, 04 Dec 2019 13:44:35 +0000

Bocage et cultures : un mariage harmonieux sur le Kervulu

Year

2001

s.le-grumelec Wed, 12/04/2019 - 14:44

Authors

Le Télégramme

Case study(ies)

Reconstruction of the hedgerow on the Léguer basin

NWRM(s)

Buffer strips and hedges

Source type

Other

Bocage

s.le-grumelec — Wed, 04 Dec 2019 13:43:15 +0000

Bocage

Year

consulted 02/12/2019

s.le-grumelec Wed, 12/04/2019 - 14:43

Authors

Bassin versant Vallée du Léguer

Case study(ies)

Reconstruction of the hedgerow on the Léguer basin

NWRM(s)

Buffer strips and hedges

Source type

Website

Le suivi de la qualité de l’eau

s.le-grumelec — Wed, 04 Dec 2019 13:42:18 +0000

Le suivi de la qualité de l’eau

Year

consulted 02/12/2019

s.le-grumelec Wed, 12/04/2019 - 14:42

Authors

Bassin versant Vallée du Léguer

Case study(ies)

Reconstruction of the hedgerow on the Léguer basin

NWRM(s)

Buffer strips and hedges

Source type

Website

L’eau en Loire Bretagne, les trophées de l’eau en Loire Bretagne 2009

s.le-grumelec — Wed, 04 Dec 2019 13:38:58 +0000

L’eau en Loire Bretagne, les trophées de l’eau en Loire Bretagne 2009

Year

2009

s.le-grumelec Wed, 12/04/2019 - 14:38

Authors

Agence de l’eau Loire Bretagne

Case study(ies)

Reconstruction of the hedgerow on the Léguer basin

NWRM(s)

Buffer strips and hedges

Source type

Other

Retour d'expérience - Le programme Breizh Bocage au service de la restauration de l’eau

s.le-grumelec — Wed, 04 Dec 2019 13:37:59 +0000

Retour d'expérience - Le programme Breizh Bocage au service de la restauration de l’eau

Year

Consulted 15/11/2019

s.le-grumelec Wed, 12/04/2019 - 14:37

Authors

Renault Pascal

Publisher

Revue Sciences Eaux et Territoires

Case study(ies)

Reconstruction of the hedgerow on the Léguer basin

NWRM(s)

Buffer strips and hedges

Source type

Website