WW-R-2: Investment in inland watercourse flood protection - case study

The picture shows a water body on the edge of which a construction measure is being carried out. The edge of the bank is open ground where two dredgers are active.Click to enlarge
Flexible technical/non-technical flood protection measures support climate change adaptation
Source: Photograph: © Ewald Fröch / stock.adobe.com

2019 Monitoring Report on the German Strategy for Adaptation to Climate Change

Table of Contents

 

WW-R-2: Investments in floodwater protection for inland waterways – case study

In the course of the past ten years, 259.71 million Euros were granted to Hesse by the Federal Government and invested in flood protection. This figure does not reflect any investments by local authorities themselves. As far as Hesse is concerned, its obligation extends only to the maintenance of old meanders of the river Rhine (Old Rhines). Non-technical flood protection measures regarding 1st order waters in Hesse are therefore carried out to a limited extent only (not represented in the chart).

The stacked column graph shows the development of grants to municipalities for technical and non-technical flood protection on second- and third-order water bodies as well as the expenditure of funds for conceptual preparatory work on first-order water bodies and for technical flood protection measures on first-order water bodies from 2000 to 2017. The expenditures fluctuate from year to year; they were highest in 2005 and lowest in 2016.
WW-R-2: Investments in floodwater protection for inland waterways – case study

The stacked column graph shows the development of grants to municipalities for technical and non-technical flood protection on second- and third-order water bodies as well as the expenditure of funds for conceptual preparatory work on first-order water bodies and for technical flood protection measures on first-order water bodies from 2000 to 2017. The expenditures fluctuate from year to year; they were highest in 2005 and lowest in 2016. The grants to the municipalities show no trend, the expenditures for conceptual preparatory work on first-order water bodies show a quadratically increasing trend, and those for technical flood protection measures on first-order water bodies show a quadratically decreasing trend.

Source: Hessisches Ministerium für Umwelt; Klimaschutz; Landwirtschaft und Verbraucherschutz (budget account)
 

Back to natural structures of water bodies

Floodwater events are a natural phenomenon. Human interventions such as separating alluvial meadows from rivers, straightening rivers, clearfelling of alluvial forests and property development in flood plains entail that the topography of the landscape is less able to retain floodwater thus accelerating run-off into watercourses and standing water bodies. It is to be expected that progressive climate change will increase the flooding risks of flowing waters. This increases the importance of floodwater risk management as embedded in the European Flood Risk Management Directive (FRMD) enacted in 2007 thus giving it legal status.

By late 2015 floodwater risk management plans, agreed and approved at national and international level, had been, for the first time ever, developed for all German river basins. Every six years, these plans have to be subjected to revision and updating by those Länder which are responsible for floodwater precautions; this work has to be done taking into account the anticipated impacts of climate change. To this end it is necessary to create or update maps for areas in danger or at risk, to lay down objectives for dealing with extant risks and to design and enhance action plans to achieve those objectives. Such plans contain measures for technical floodwater protection, restoration of retention areas and the rehabilitation of near-natural structures of water bodies/watercourses.

Additional measures such as demarcation and designation of floodwater areas or preliminary planning work for the implementation of operational measures for floodwater protection are embedded in the Wasserhaushaltsgesetz (WHG/Water Resources Act). In respect of such planning and conceptional measures for the state of Hesse alone the cumulative expenditure amounted to 6.85 million Euros in the course of the past ten years. Nevertheless, a holistic approach plays an important role in other areas too, such as behavioural precautions and precautions in the building sector, as well as development planning, improvements in floodwater forecasting, crisis management and risk-adapted reconstruction.

Technical flood protection defences such as dams, dykes and walls, rain and flood control reservoirs, barrages, pumping stations and flood channels are employed for the retention, passage and redirection of water. Some Länder such as Baden-Württemberg or Bavaria are already basing their design efforts for flood protection defences on a ‘Lastfall Klimaänderung’ (potential climate-change related burden). In order to account for ‘climate change factors’ such as a hundred-year flood event, a safety margin is added to the currently valid design value as a safeguard against any rising floodwater risks in the future. In Hesse investments in technical flood protection have declined in recent years, because the prolonged dyke rehabilitation work in the areas of Rhine and Main are now essentially completed.

In addition to measures for technical flood protection, also non-technical measures are gaining in importance, because natural or near-natural structures of watercourses are able to retain water, stabilise the water regime and mitigate moderate flood events occurring in flowing waters. Restoration of natural or near-natural conditions is therefore promoted wherever possible. Meandering rivers and streams reduce flow rates and attenuate floodwater run-off peaks. Where the bed of a watercourse is permeable, consisting of types of sand and gravel, this enables the natural exchange between surface- and groundwater and is thus able to buffer, at least in part, floodwater peaks or water shortages. Cut-off meanders, alluvial meadows and flood plains in the vicinity of watercourses, are able to absorb part of the floodwater run-off. While many restoration or rehabilitation measures are often informed mainly by nature conservation objectives, they also help to reduce floodwater risks. Accordingly, the federal programme ‘Blaues Band Deutschland’ (Germany’s blue ribbon) adopted by the Federal Cabinet in February 2017, made specific reference to the social benefits of rehabilitating watercourses for the purpose of adaptation to climate change impacts. One of the core challenges regarding non-technical flood protection continues to be the availability of additional retention areas which are safe to be flooded in a floodwater event.

Within the scope of the Joint Task entitled ‘Improvement of Agrarian Structures and Coastal Protection’ (IASCP), the Federal Government reimburses the Länder with 60 % of their expenditure in respect of constructing new and reinforcing extant flood protection defences, for relocating dykes and for measures to develop near-natural watercourses/water bodies. The national flood protection programme was designed jointly at Federal and Länder level after the June 2013 floods in the areas of Elbe and Danube. Its purpose is to advance the implementation of supraregional measures for floodwater protection in river basins. The Federal Government uses the special framework plan (SRP) entitled ‘Präventiver Hochwasserschutz’ (preventative flood protection) to support the Länder in their implementation of measures for the realignment of dykes and the restoration of natural retention areas by means of flood control reservoirs and polders. For the first time ever, the Federal Government is promoting the purchase of retention areas. In order to implement flood protection measures in respect of 1st order waters, the Länder use further funds from their own budgets, in addition to the resources available under IASCP and SRP. Furthermore, individual Länder grant funding to local authorities within the framework of their responsibility for 2nd and 3rd order waters.

 

Interfaces

WW-I-3: Floodwater

BD-I-3: Restoration of natural flood-plains

WW-R-3: Riparian vegetation of small, medium-sized water bodies-case study

 

Objectives

Restoration and redynamisation of alluvial meadows in river basins (DAS, ch. 3.2.3)

Protection from increasing floodwater risks by strengthening passive safeguarding measures (especially keeping land free from property development) and active run-off control, substantial expansion of retention areas (DAS, ch. 3.2.14)

Designation of floodwater areas (WHG, § 76)