Flash floods

EXAMPLE: Constructed wetlands to compensate for urbanization in souther Finland (FIN)

nst — Thu, 16 Feb 2017 09:00:50 +0000

EXAMPLE: Constructed wetlands to compensate for urbanization in souther Finland (FIN) nst Thu, 02/16/2017 - 10:00

In Finland urban wetlands are being implemented to help improve water quality, absorb storm water volume and flow control, and improve the land-water habitats for urban communities. The wetlands are designed to respond to the needs and negative impacts of urbanization and therefore, public acceptance and multifunctional benefits are central to the design and implementation of the wetlands. The acceptance and understanding of the importance of urban dwellers is important and thus the project sought to demonstrate several benefits of functional wetlands.

Based on Wahlroos et al. (2015): Urban wetland parks in Finland: improving water quality and creating endangered habitats. In: Urban wetland parks in Finland: improving water quality and creating endangered habitats. In: International Journal of Biodiversity Science, Ecosystem Services & Management Volume 11, Issue 1: Pages 46-60

General description

Urbanization is affecting water quality and there is increasing severity of flooding and drought periods in Southern Finland. This is expected to become worse because of climate change. During flooding events, run off from rain and melting snow are quickly carried over urban surfaces and overwhelm receiving streams. Habitat degradation is occurring as harmful water from urban areas is transferred into connected habitats. These urban streams in turn cause flooding and channel erosion. The creation of wetlands is an alternative ecosystem approach to conventional responses that have been to seal natural waterways into culverts or clearing, and stabilization for augmented conveyance and erosion control.

Two urban wetlands, the Nummela Gateway and the Nummela Niittu were designed and implemented. The wetlands are 6ha and 7ha respectively and are within 550 ha of the urbanized Kilsoi stream watershed in the catchment of Lake Enäjärvi, in the Nummela community, Municipality of Vihti, Southern Finland. The lake has poor water quality from algal blooms and fish kills that result from runoff from its catchments and phosphorus load from human activities. The Stream Kilsoi is an inland clay-soil stream that drains into the Baltic Sea. The habitat type and clay-stream is red listed in the Red list Assessment of Finnish habitat types as critically endangered.

Ecosystem-based aspects

The creation of wetlands is an ecosystem approach and replaced hard infrastructure and conventional responses that have previously been implemented in the area to control storm water volume. In the past, the convention has been to seal natural waterways into culverts or clearing, and stabilization for augmented conveyance and erosion control.

The two wetlands, Nummela Gateway and the Nummela Niittu, were established over five years and closely monitored. The ecosystem service that was deemed most important for the wetlands to provide was water quality management. Water treatment by wetlands depends on the plants and their associated microbes. Storm water and flooding events are the main carriers of potential pollutants from urban areas, and thus a high density and diversity of plans and microbes is necessary. In this case, the native origin of the plants was also found to be important to protect urban streams from the erosive effects of storms and snowmelts. Plant self-establishment occurred quickly and construction only required the monitoring of water levels, especially during winter. The existing shoreline and old drainage ditches acted as a seedbank and no maintenance of native plants was necessary.

In addition to improving biodiversity, water quality improvements were also achieved. There was an increase in phosphorus reduction after the third year. Despite that the Gateway wetland is just 0.1% of its 550 ha watershed area, it does achieve an annual 10% for total phosphorus reduction.

Key lessons learnt

The establishment of two wetlands near to an urbanized area was able to mitigate against various challenges stemming from urbanization. The Gateway and Niittu wetlands were successful in creating high biodiversity at the clay-stream habitats and relied on little human maintenance due to the naturally occurring habitat which was conducive to wetland creation and existence.

Some compromises were made in order to ensure the acceptance of the wetlands and their appreciation and support by the community. Both wetlands were designed to accommodate open water areas for recreational purposes and thus do not fulfill the most efficient capacity for pollution removal.

Despite the establishment of the wetlands, they do not address source control directly which remains an issue. If action is taken to reduce pollution at the source, then the wetlands will be more productive in response.

Continued monitoring during and after the establishment of the wetlands allowed for there to be definitive conclusions on the impact of the created wetlands on water pollution mitigation, self establishment of vegetation, and biodiversity development. Water quality improvements were demonstrated with continuous monitoring which would not have been deciphered via discrete water sampling.

Relevant case studies and examples

Wetland restoration

Literature sources

Main source: Outi Wahlroos, Pasi Valkama, Emmi Mäkinen, Anne Ojala, Harri Vasander, Veli-Matti Väänänen, Anna Halonen, Leena Lindén, Petri Nummi, Hannele Ahponen, Kirsti Lahti, Teuvo Vessman, Kari Rantakokko & Eero Nikinmaa (2015): Urban wetland parks in Finland: improving water quality and creating endangered habitats. In: International Journal of Biodiversity Science, Ecosystem Services & Management Volume 11, Issue 1: Pages 46-60

Measure category

Mitigation

EXAMPLE: MOSE system of mobile flood barriers, Venice (IT)

nst — Tue, 07 Feb 2017 08:35:19 +0000

EXAMPLE: MOSE system of mobile flood barriers, Venice (IT) nst Tue, 02/07/2017 - 09:35

Flash floods

Coastal floods or storm surges

Reduction

Water flow regulation

Hold the line

Grey infrastructure

Venice, Italy, is a city famous around the world for not only its stunning canals and historic buildings, but also for its high vulnerability to flooding. The MOSE system of mobile flood barriers is a bold initiative intended reduce risk, preserve the cherished cityscape, and protect the entire Venice Lagoon from flooding.

Based on information from the project website

General description

The MOSE (short for “Modulo Sperimentale Elettromeccanico” in Italian) system consists of four mobile barriers closing off three inlets in the Venice Lagoon. The barriers themselves are made up of 78 flap gates that are installed at the bottom of the inlets to separate the lagoon from the sea when raised. The system takes approximately 30 minutes to open and can be closed in 15 minutes, but takes on average five hours to close. Once raised, the barriers are able to withstand three meters of high tide. The barrier at the Malamocco inlet even has a lock system installed to allow merchant and industrial ships to cross while the MOSE system is in operation to reduce interference on port activities.

Seasonal high water is a constant threat to Venice, and the city has adapted with raised walkways, waterproofed buildings, and power outlets installed halfway up the wall in businesses and homes. Flooded scenes of a usually picturesque St Mark’s Square can be explained due to the fact that it is the city’s lowest point. However, more extreme high tides that occur roughly every three years and can raise water levels by over a meter present a much greater risk to Venice’s cultural heritage and justify a system such as MOSE.

Governance aspects

Venice and its Lagoon is a UNESCO World Heritage Site, which makes its protection even more important. The MOSE project was implemented by the Italian Ministry of Infrastructure and Transport and managed by the Consorzio Venezia Nuova for the purposes safeguarding Venice and the lagoon. The decision to construct the mobile flood barriers was made after collaboration between all levels of government and consideration of various other coastal defence measures.

Innovative aspects

The MOSE system in its entirety is an impressive and innovation response to the threat of coastal flooding and erosion, both from a construction and coordination standpoint. The hydrological and geophysical profile of the Venice Lagoon needed to be fully considered when designing the barriers and their final locations.

While the MOSE Control Centre uses advanced technology to predict flooding, model the effects of gate manoeuvres, predict port traffic, determine warning levels, and so on, the MOSE project also employs other smaller scale measures to optimise the overall goal of flood risk reduction in the lagoon. These local defences consist of raising quaysides, roads, walkways, and installing smaller gates in the urban canals in the lagoon settlements, known as the “Baby MOSE” gates. This holistic and comprehensive approach to encouraging protection for the entire lagoon, aside from that which is provided by MOSE, is also innovative.

Key lessons learnt

It is not easy to construct such large-scale defences in fragile environments, but, as the MOSE system illustrates, sometimes this approach is necessary to provide significant long-term protection. Venice represents an especially vulnerable coastal city with globally significant heritage sites and a very active tourism industry. With so much at risk, the MOSE system will ensure businesses, residents, and visitors will be able to enjoy the fabled canals, palaces, and plazas without the threat of flooding and building damage. The implementation of local defences diversifies the resilience of the settlements in the lagoon and increases the rate of success for the MOSE project.

Relevant case studies and examples

Flood and storm surge barrier

EXAMPLE: Early warning system in Sogn og Fjordane (NOR)

nst — Wed, 25 Jan 2017 15:39:06 +0000

EXAMPLE: Early warning system in Sogn og Fjordane (NOR) nst Wed, 01/25/2017 - 16:39

Riverine or slow rise floods

Flash floods

Estuarine floods

Coastal floods or storm surges

Urban floods

Flood Forecasting and Warning

Non-structural measure

The county of Sogn og Fjordane frequently experiences avalanches and landslides, storm surges and flooding. A demonstration project explored the potential for an effective, reliable and cost-efficient early warning system that has a multi-hazard approach and makes use of location and population-based communication technologies, such as mobile phones, as well as social media such as Facebook and Twitter. The system was tested with a sample warning followed by a survey and data analysis to judge its efficacy.

Based on information from the Climate-ADAPT website.

General description

Sogn og Fjordane is a coastal, mountainous region of Norway that boasts hundreds of thousands of tourist visits annually. Several communities in Sogn og Fjordane are facing numerous hazards such as flooding, avalanches, rock slides and other extreme weather events, that might be exacerbated by climate change. To respond to the challenge an early warning system was developed and tested within a EU research project. The multi-hazard warning system aimed at optimising rescue and other emergency services provided by the county. Due to tourism, it aims to be a cost-effective method reaching all people in the geographic area and not only residents.

A public warning exercise was carried out in 2010 with 2,500 mobile phones receiving the alert as text message and 322 fixed line phones in Aurland received the alert as voice message. The warning exercise was visible on Facebook for 2 hours and received 201,849 viewings. A post-exercise survey was carried out online and a door-to-door survey was conducted in parts of the area to assess the public’s thoughts on the exercise. The population warning exercise was evaluated to measure the efficiency of the warning system by combining an electronic evaluation form and a door-to-door survey.

Key lessons learnt

The project demonstrated how an existing county-encompassing organization could be used to issue the population warning. While the technical aspects of people-centred warning systems are at large readily available, issues concerning confidentiality legislation and system regulations must be solved before successfully implementing efficient location-based warning systems. In order to use social media during crisis situations, the projected concluded that research is needed.

Relevant case studies and examples

Early warning systems

Measure category

Preparedness

EXAMPLE: Reopening Waterways in Oslo (NOR)

nst — Mon, 23 Jan 2017 15:19:39 +0000

EXAMPLE: Reopening Waterways in Oslo (NOR) nst Mon, 01/23/2017 - 16:19

Riverine or slow rise floods

Flash floods

Urban floods

Channel, Coastal and Floodplain Works

Combined approach (grey + green)

As in many other cities, the former dominating strategy for Oslo’s rivers and streams was to enclose them for practical reasons. This approach has changed and the City is actively reopening waterways to make them accessible for people, facilitate increased habitat for biodiversity and handle storm water more efficiently.

Based on information provided by the city Oslo.

General description

The City of Oslo is characterized by urban waterways and their tributaries. Up until the 1980s, the waterways were considered problematic for the sewage system and an obstacle for efficient exploitation of land. Hence large sections of waterways were put in culverts. These culverts have predefined capacities that can cause problems if urban flooding cannot cope with these predefined capacities.

The City of Oslo has decided to reopen closed rivers and streams wherever it is possible and expedient. In order to formalise and streamline the municipal cooperation regarding reopening projects, the relevant municipal agencies have, in collaboration, developed a management document that outlines the principles for reopening projects including a list of prioritised projects. The list is updated annually.

The “Teglverksdammen” Project

In August 2015 a large reopening project in Teglverksdammen was completed. Ca. 650 meters of the Hovinbekken stream was reopened for EUR 10 million. Teglverksdammen is planned and designed as a natural cleaning system, with several sedimentation basins, stream with water rapids, a small lake and shallow waters with dense vegetation. As a result, Teglverksdammen cleans water, provides habitat for biodiversity and has become a popular recreation area for people.

Relevant case studies and examples

Reopening culverts

Measure category

Mitigation

Rainwater harvesting

nst — Fri, 02 Dec 2016 11:05:01 +0000

Rainwater harvesting nst Fri, 12/02/2016 - 12:05

Riverine or slow rise floods

Flash floods

Surface Water Management

Combined approach (grey + green)

Water harvesting is when rainwater or stormwater is collected and stored for productive use later. It can be used for agriculture, drinking and more. Historically, rainwater harvesting is a common practice and has been used by many communities to support agriculture in sensitive and variable climates.

Based on kindly provided information by UNEP's "Green Infrastructure Guide for Water Management: Ecosystem-based Management Approaches to Water-related Infrastructure Projects " (UNEP, 2014)

As a result of its widespread and historical use, many varieties of harvesting water exist and depend on the area available for catchment as well as the intended post-collection use. Water harvesting techniques can be divided in two main types: in situ and ex situ.

In situ rainwater harvesting is a technique that increases the capacity of the soil to store water, thus collecting water where it lands. In situ collection ensures that rainwater remains where it falls with little distance between capture and usage areas. Some examples of in situ water harvesting include terracing, pitting and conservation tillage practices. These measures are also used for for soil conservation (UNEP and SEI 2009).

Ex situ water harvesting is a technique where water is collected in an area external to where it falls and is stored for later use. Ex situ water harvesting is often used in urban areas natural soil surfaces or rooftops, roads and pavements in urban areas. Examples include capturing and storing water in dams, wells, ponds, cisterns, etc. (UNEP and SEI 2009).

Benefits & Co-Benefits

In situ water harvesting has multiple benefits. It allows for the collection of water in soil, thus increasing water infiltration and holding capacity which results in improved soil fertility for agriculture and/or biodiversity. Other benefits can include reduced runoff from slopes and facilitates groundwater recharge (Agriwaterpedia 2014).

Ex situ benefits are usually related to storing excess water, particularly stormwater runoff for productive use later. In urban areas, the reduced stormwater runoff volumes also contribute to minimizing the amount of pollutant loads entering stormwater collection systems, helping to prevent potentially damaging effects on water quality (EPA 2013). In addition, it contributes to water conservation, reducing the pressure on surface water sources and groundwater. When used for irrigation purposes in households, the harvested water also enhances groundwater recharge. In urban areas, reduced energy requirements for water treatment and transport can contribute to better air quality, and reduced CO2 emissions from local power plants. Even if treated for potable use, rainwater, in most cases, requires less energy than conventional water treatment and distribution.

Costs

Water harvesting measures vary in cost depending on type, design and scale. For example, in situ solutions in rural areas using traditional methods may be low cost and only incur the cost of labor and time. For ex situ methods, the building of storage tanks, cisterns, pumps, etc., will incur costs of its own. The scale is also a factor.

The scale of water harvesting methods can also influence the hydrological regime of a river, particularly if its large-scale. For example, water harvesting that significantly reduces surface runoff may increase groundwater recharge and evaporation losses. This may negatively impact downstream water users, including ecosystems. When multiple users are involved and scale is significant, it is important to undertake comprehensive planning and with proper knowledge of the hydrological system in question.

Literature sources

Agriwaterpedia (2014). Available from http://agriwaterpedia.info/wiki/Water_harvesting.

UNEP and SEI (2010). AdaptCost Briefing Paper 3: Coastal Adaptation – Africa Review and New Estimates.

EPA (2013). United States Environmental Protection Agency, Rainwater Harvesting: Conservation, Credit, Codes, and Cost. Literature Review and Case Studies.

Measure category

Mitigation

Spatial Planning and Integrated Coastal Zone Management (ICZM)

nst — Thu, 10 Nov 2016 12:42:35 +0000

Spatial Planning and Integrated Coastal Zone Management (ICZM) nst Thu, 11/10/2016 - 13:42

Riverine or slow rise floods

Flash floods

Estuarine floods

Coastal floods or storm surges

Urban floods

Erosion

Emergency Event and Contingency Planning

Public Awareness and Preparedness

Non-structural measure

Coastal and marine environments are usually characterized by beautiful landscapes and rich ecosystems of great importance, offering elements such as rich biodiversity. They also attract human activities such as tourism and industrial uses. However, the co-existence of human activities and natural resources often creates conflicts of use in the coastal zone.

Management policies are an important means of implementing planning in order to minimise, prevent or resolve use conflicts. The development of a coastal and marine spatial planning system presents an opportunity for the implementation of an overall strategy of conservation, sustainability and management to maximise future economic profit.

Based on "Papatheochari, Dora (2008): Spatial Planning and Integrated Coastal Zone Management. Available from http://www.coastalwiki.org/wiki/Spatial_Planning_and_Integrated_Coastal_Zone_Management [accessed on 10-11-2016]"

Spatial Planning

Previously, the role of spatial planning focussed intensively on economic and social development. Gradually, environmental dimensions were taken into account, especially through the appearance of sustainable development in environmentally important areas. Spatial planning in Europe promotes environmental sustainability, examining the concept of development which meets environmental, social and economic needs of present and future generations as well as policy and planning instruments to promote such development. It also encourages spatial integration of development perspectives demonstrating how social cohesion, regional innovation and sustainable development can interplay in real planning situations, using policies and planning tools, such as Environmental Impact Assessment and European Spatial Development Perspective.

Through the use of Geographical Information Systems (GIS), spatial planning has been used to define and map coastal and marine areas. It is essential to examine not only environmental impacts of individual activities but to research cumulative effects of multiple activities occurring in an area. Mapping coastal and marine areas in detail allows the opportunity to identify those areas at particular risk from possible pollution or excessive disturbance and to examine in detail how many activities are occurring.

Integrated Coastal Zone Management

Integrated Coastal Zone Management (ICZM) is a dynamic, continuous and iterative process designed to promote sustainable management of coastal zones. ICZM projects cover various geographical areas, from local regions to spatially extensive coastal areas. The “Integrated” in ICZM refers both to the integration of objectives and to the integration of the multiple instruments needed to meet these objectives. ICZM includes the integration of all relevant policy areas, sectors, and levels of administration as well as the terrestrial and marine components of the geographical area under consideration. The word 'Integrated' also refers to four types of integration: spatial, temporal, vertical and horizontal.

Comparing Spatial Planning and Integrated Coastal Zone Management

A common goal of spatial planning and ICZM is to define, develop and protect coastal zones; ICZM is most common at the local scale while spatial planning is often applied at larger scales. Both share policies with the same goal, the resolution of land use conflicts for the development and conservation of coastal and marine environment. Spatial planning at the national level is essential in order to examine the impact of human activities in urban and regional coastal zones. Coastal Zone Management is becoming increasingly necessar because of the increasing importance of coastal and marine exploitation/development and protection.

An enabling environment at the European level could provide the framework in which countries can develop more appropriate integrated coastal zone management policies, including investment strategies, integrated development plans (spatial and functional) and resource management strategies.

The most important issue for both spatial planning and ICZM are the effective and successful implementation of planning systems and policies as well as a better understanding and definition of coastal and marine areas. A common perspective of European coasts must be adopted in order to improve management and planning of activities in coastal and marine areas.

Relevant case studies and examples

EXAMPLE: A participatory adaptation planning approach, Cascais (PT)

EXAMPLE: Developing an Attica Wetland Action Plan (GR)

Measure category

Prevention

Flood and hazard forecasting

giacomo.cazzola — Thu, 15 Sep 2016 12:13:22 +0000

Flood and hazard forecasting giacomo.cazzola Thu, 09/15/2016 - 14:13

Riverine or slow rise floods

Flash floods

Estuarine floods

Coastal floods or storm surges

Urban floods

Flood Forecasting and Warning

Non-structural measure

Flood forecasting is an essential tool for providing people still exposed to risk with advance notice of flooding, in an effort to save life and property.

Based on: Jha, Abhas K., Robin Bloch, and Jessica Lamond. Cities and Flooding: A Guide to Integrated Urban Flood Risk Management for the 21st Century. World Bank Publications, 2012.

Different flood forecasting service models exist based on the needs of end users: a system may be developed for the public or strictly dedicated to the authorities. There is no single consistent approach worldwide but the basic principles of a good warning system are shared by all. These comprise:

Better detection in times of need well before the actual event occurs
Interpretation of the detected phenomena and forecasting this to the areas likely to be affected
Dissemination of the warning message to the relevant authorities and public via the media and other communication systems.

The fourth and final aspect is to encourage the appropriate response by the recipients by preparing for the upcoming event. This can be improved through flood response planning by people at risk and their support groups.

Uncertainty in flood forecasting

Models, by definition, are approximations of reality. As described earlier, all models suffer from a certain level of approximation or uncertainty in spite of powerful computing systems, data storage and high level technologies. Decision makers have to consider the effects of uncertainties in their decision-making process. Errors in forecasting of an event, for example stage or time of arrival, may lead to under-preparation (at the cost of otherwise avoidable damage) or over-preparation (resulting in unnecessary anxiety). The balance between failure to warn adequately in advance and the corrosive effects of too many false alarms must be carefully managed.

The reliability of flood forecasting models relies on the quantification of uncertainty. All natural hazards are uncertain. The various sources that give rise to uncertainty in forecasting and early warning can be classified (Maskey. 2004) as:

Model Uncertainty
Parameter Uncertainty
Input Uncertainty
Natural and Operational Uncertainty.

It is necessary to gain a better understanding of the options available to deal with the uncertainties within the system arising from these different sources.

In order to produce a forecast, the initial conditions are typically determined by means of observations from rain gauges; these may, however, be unevenly spaced throughout the catchment, leading to uncertainty as to the total volume of rainfall. Where hydrologically important areas (such as steep slopes) are unrepresented, the model may utilize an interpolation method (introducing another element of uncertainty) in order to estimate run-off volume and peak flows. More sophisticated modeling can address these issues, but this in turn may demand high processing speeds and lengthy run-times.

To offset some of this uncertainty, operational flood forecasting systems are moving towards Hydrological Ensemble Prediction Systems (HEPS), which are now the ‘state of the art’ in forecasting science (Schaake et al. 2006; Thielen et al. 2008). This method formed part of initiatives such as HEPEX (Hydrological Ensemble Prediction EXperiment) which investigated how best to produce, communicate and use hydrologic ensemble forecasts for short, medium and long-term predictions. Despite its demonstrated advantages the use of this system is still limited: it has been installed on an experimental basis in France, Germany, Czech Republic and Hungary.

To deal with the uncertainty in spatio-temporal distribution and prediction of rainfall for extreme events, especially through radar derived data, a promising approach has been to combine stochastic simulation and detailed knowledge of radar error structure (Germann et al. 2006a, 2006b, 2009; Rossa et al. 2010). Radar ensembles have the potential benefits of increasing the time for warning especially for flash floods (Zappa et al. 2008). Advanced techniques, such as disdrometer networks (equipment capable of measuring the drop size, distribution and velocity of different kinds of precipitation) and LIDARs are being used to capture small scale rainfall phenomenon, whilst satellite remote sensing is more appropriate for regional and global level applications. A combination of all these methods and blending information is considered to be the most promising way forward.

There are a several useful examples of such systems:

DELFT-FEWS: one of the state of the art hydrological forecasting and warning systems developed by Deltares. This system is an integration of a number of sophisticated modules specialized in their individual capacities and the system is highly configurable and versatile. The system can be used as a standalone environment, or it can be used as a compliant client server application. Through its advanced modular system FEWS has managed to reduce the challenges like handling and integration of large datasets to a considerable extent.
Automated Local Evaluation in Real Time (ALERT) is the method used within the AUG member states to transmit data and information using remote sensors for warning against flash floods.
Central America Flash Flood Guidance is an example of regional flash flood warning. The national Hydrologic Warning Council (NHWC) has member countries across North America and many parts around the world; it is also a major organization in data dissemination for early warning for flood events.
The Mekong River Commission flood forecasting system, discussed above, has been operating since 1970. It is an integrated system which provides timely forecasting to its member countries. It consists of three main systems of data collection and transmission, forecast operation and information dissemination at both national and regional level.
The Southern African regional model for flood forecasting Stream Flow Model (SFM) has been applied after the Mozambique flood in 2000. The USGS along with Earth Resource Observation System (EROS) supports monitoring and modeling capacities of Southern African Countries.
Regional Water Authority of Mozambique (ARA-Sul) is responsible for issuing flood warning and real time forecasting. The system is operational in Southern Africa with a mean area of 3,500 square kilometers. A simplified flood warning system, the Mozambique Flood Warning Project, is specially tailored to the needs of the local population. It also involves the local people and trains them to install, monitor and maintain the structures.
Hydro Met Emergency Flood Recovery Project is used in Poland.
Bhutan’s Glacial Lake Outburst Flood (GLOFs) Iridium Satellite Communications is used as the telemetry back-bone for Bhutan’s GLOF Early Warning Project.
In the Toronto region of Canada, the Toronto and Region Conservation Authority (TRCA) flood forecasting and warning system is used; this is a scalable flood warning system including web-based data and video for nine watersheds.
The Automatic Dam Data acquisition and alarm reporting system, is the Puerto Rican System to obtain, monitor and analyze, in real- time, critical safety parameters such as inflows, outflows, gate openings and lake elevations for 29 principal reservoirs
Central Water Commission (CWC) in India provides the Turnkey Flood forecasting system across 14 states having 168 remote sites in six river basins.

Literature sources

Maskey, S., Guinot, V. and Price, R.K. 2004. “Treatment of precipitation uncertainty in rainfall-runoff modeling: a fuzzy set approach.” Advances in Water Resources 27 (9): 889-98.

Schaake, J., Franz, K., Bradley, A., and Buizza, R. 2006. “The Hydrological Ensemble Prediction Experiment (HEPEX).” Hydrological and Earth System Sciences Discussions 3: 3321–32.

Thielen, J., Schaake, J., Hartman, R. and Buizza, R. 2008. “Aims, challenges and progress of the hydrological ensemble prediction experiment (HEPEX) following the third HEPEX workshop held in Stres 27-29 June 2007.” Atmospheric Science Letters 9: 29-35.

Germann, U., Berenguer, M., Sempere-Torres, D., and Salvadè, G. 2006a. “Ensemble radar precipitation estimation — a new topic on the radar horizon.” Proceedings of the 4th European Conference on Radar in Meteorology and Hydrology (ERAD). Barcelona. September 18–22, 2006. 559–62.

Germann U., Galli, G., Boscacci, M, and Bolliger M. 2006b. “Radar precipitation measurement in a mountainous region.” Quarterly Journal Royal Meteorological Society 132: 1669–92.

Germann, U., Berenguer, M., Sempere-Torres, D., and Zappa, M. 2009. “REAL — Ensemble radar precipitation estimation for hydrology in a mountainous region.” Quarterly Journal Royal Meteorological Society 135: 445–56.

Rossa, A. M., Cenzon, G. and Monai, M. 2010. “Quantitative comparison of radar QPE to rain gauges for the 26 September 2007 Venice Mestre fl ood.” Natural Hazards and Earth System Science 10 (2): 371–7.

Zappa, M., Rotach, M.W., Arpagaus, M., Dorninger, M., Hegg, C., Montani, A., Ranzi, R., Ament, F., Germann, U., Grossi, G., Jaun, S., Rossa, A., Vogt, S., Walser, A., Wehrhan, J., and Wunram, C. 2008. “MAP D-PHASE: Real-time demonstration of hydrological ensemble prediction systems.” Atmospheric Science Letters 2: 80–7.

Measure category

Preparedness

Evacuation planning

giacomo.cazzola — Thu, 15 Sep 2016 11:39:02 +0000

Evacuation planning giacomo.cazzola Thu, 09/15/2016 - 13:39

Riverine or slow rise floods

Flash floods

Estuarine floods

Coastal floods or storm surges

Urban floods

Emergency Event and Contingency Planning

Non-structural measure

To minimize the loss of lives and reduce other flood impacts, an area should be evacuated when the depth of standing water due to flooding is already or is expected to become high. Such floods are defined as those which are expected to cause buildings, including residential houses, to be washed away or seriously damaged by the flooding.

Based on: Jha, Abhas K., Robin Bloch, and Jessica Lamond. Cities and Flooding: A Guide to Integrated Urban Flood Risk Management for the 21st Century. World Bank Publications, 2012.

Organizational aspects of evacuation planning

An interdisciplinary planning organization must be set up covering the key institutions that have remits relating to disaster and specifically flood management. This organization can be a Community Flood Management Committee (CFMC). In addition to the CFMC, evacuation centers should also be established in appropriate settlements.

The members of the CFMC should have knowledge of evacuation and rescue operation and emergency, including medical care (if this is not the case, then basic training should be provided to them). Evacuation plans should be prepared after discussion with the community. Participatory planning will increase people’s awareness and ability to cope and manage flood risk. The evacuation plan should be available to all members of the community, including the most vulnerable.

Dissemination of information on flood risk and flood preparedness requires the organization of regular community meetings. Such meetings can take place before the onset of the rainy season, or monsoon. It is vital that evacuation drills will be held regularly to test the effectiveness of the evacuation plans.

The evacuation plan should delineate an escape route and also identify small- scale works that may be needed to make the route safer. Such works can be executed in cooperation with the community as well as with external support. The evacuation plan should also determine modes of transport and access routes for evacuation and rescue operations and relief projects. In addition, the evacuation plan should identify open spaces and buildings to be used as evacuation centers. These can function as described by Arnold, Chen, Deichmann et al. (2006: 149).

Temporary shelters and refuges
Hospitals, possibly in existing buildings with stored supplies and basic medical equipment
Information centers, with uninterrupted linkages to the central communications system
Supply distribution points for basic survival supplies, such as water, food, and blankets
Sanitary facilities, including toilets, showers, and waste disposal units.

To develop evacuation plans and carry out the tasks outlined above, maps showing the most exposed areas to flood risk should be available. EWS should also be in place to give advance notice of an impending flood allowing evacuation plans to be put into action. Even when a flood is not as severe as predicted, these preparations help test evacuation plans and inform the communities as to the nature of flood risk.

Provision of flood shelters and refuges

As stated in UNDP (2009:36): “Shelter is likely to be one of the most important determinants of general living conditions and is often one of the largest items of non-recurring expenditure.”

Shelters and refuges must, as a minimum:

Provide protection from the climate conditions
Provide space to live and store personal belongings
Ensure dignity, privacy, safety and emotional security.

In most emergencies there is a common basic need for shelters or refuges. However, issues such as the type and the design of the shelter, the required materials, by whom it is constructed, and the duration it is expected to last, will vary significantly according to the situation. Vulnerability analysis can identify the basic needs and priorities of the affected population in relation to shelters. Safe areas for flood shelters or refuges may include:

Schools
Religious meeting places (such as temples, churches, mosques)
Community centers
Higher ground (such as roofs, upper floors, embankments)
Military installations
Barracks.

Location and size of shelters and refuges

The need for the location and size of shelters and refuges needs to be decided in consultation with the communities. Transportation between the shelters and social and work locations for the displaced population should be considered. Existing social practices, and the provision and maintenance of shared resources (such as water, sanitation facilities and cooking) should be taken into consideration in the design of shelters and also in the allocation of space within shelters and plots. The plot layout in the evacuation centers must preserve the privacy and dignity of individual households.

The use of materials and the type of shelter that are most commonly used among refugees or the local population is to be preferred for the construction of shelters. The design of the shelter must follow the simplest principles and structures. The provision of a solid and robust roof is the main requirement, and even when a complete shelter cannot be provided, adequate roofing should always be the priority.

Plastic tarpaulins can be easily found in most cases. Tents are not always the best type of shelter because it is not easy to live in them and also they cannot provide adequate protection against extreme climate conditions. Nevertheless, in certain cases, tents may be used as storage facilities, or to set up hospitals, schools and other facilities. The success of the evacuation centers highly depends on these facilities.

Communications between shelters and refuges

The success of an evacuation plan is highly dependent on the efficacy of the communication systems. Established communication systems must ensure that the relevant authorities are promptly informed, for example by radio or telephone. The sharing of information is essential to achieve a better understanding of the problems. Coordination among all those involved in an evacuation operation is necessary to assure that the evacuation plan is being implemented successfully.

Key lessons learnt

Evacuation plans minimize the risks and impacts of flooding for the population of cities and towns.

Relevant case studies and examples

EXAMPLE: London Mass Evacuation Framework (UK)

Literature sources

Arnold, M., Chen, R.S., Deichmann, U., Dilley, M., Lerner-Lam, A.L., Pullen, R.E. and Trohanis, Z. ed. 2006. Natural Disaster Hotspot Case Studies. Washington, DC: World Bank Hazard Management Unit.

UNDP (United Nations Development Program). 2009. Emergency Relief Items, Compendium of Generic Specifi cations. Geneva: UNDP.

Measure category

Preparedness

Early warning systems

giacomo.cazzola — Thu, 15 Sep 2016 11:06:41 +0000

Early warning systems giacomo.cazzola Thu, 09/15/2016 - 13:06

Riverine or slow rise floods

Flash floods

Estuarine floods

Coastal floods or storm surges

Urban floods

Flood Forecasting and Warning

Non-structural measure

The purpose of early warning systems (EWS) is simple. They exist to give advance notice of an impending flood, allowing emergency plans to be put into action. EWS, when used appropriately, can save lives and reduce other adverse impacts.

Based on: Jha, Abhas K., Robin Bloch, and Jessica Lamond. Cities and Flooding: A Guide to Integrated Urban Flood Risk Management for the 21st Century. World Bank Publications, 2012.

Warning systems can be used to alert relevant authorities or the public or both. The scale of a warning system can be national, based on a river basin, or local and run by volunteers. Most are stand-alone national operations, but warning systems have been developed covering several international rivers, such as the Rhine, Danube, Elbe and Mosel in Europe, the Mekong, Indus and Ganges-Brahmaputra-Meghna basins in Asia and the Zambezi in Southern Africa (United Nations 2006). However, the utility of EWS is crucially dependent on the underlying forecasting system, the quality of emergency plans and the level of preparedness of the community at risk. The quality of forecasting is also dependent on the nature of the hazard. Warning systems related to river flooding have a longer lead time than those for cyclonic events; seismic induced tsunamis may have very short warning periods. Forecasting flash flooding is also very problematic; this has implications for developing nations which are more exposed to such risks, due to the prevalence of monsoon type flooding. Whilst there is general agreement about the desirability of EWS, the implementation of such a system is necessarily subject to local factors.

Essentials for an effective EWS

The four main essentials for any flood warning system are:

Detection of the conditions likely to lead to potential flooding, such as intense rainfall, prolonged rainfall, storms or snowmelt
Forecasting how those conditions will translate into flood hazards using modeling systems, pre-prepared scenarios or historical comparisons
Warning via messages developed to be both locality- and recipient-relevant and broadcasting these warnings as appropriate
Response to the actions of those who receive the warnings based on specific instructions or pre-prepared emergency plans

Failure in any one of the four key elements of an EWS will lead to a lack of effectiveness. Inaccurate forecasts may lead to populations ignoring warnings issued subsequently.

The lack of clear warning and instruction may have resulted, for example, in the deaths of people escaping the Big Thompson Canyon flood in the US in the 1970s. Without clear instructions many people were killed trying to drive out of the canyon rather than taking the safer option of abandoning cars and climbing to higher ground.

Finally, the case of Hurricane Katrina demonstrated the scenario where clear advanced warnings failed to protect the population because the evacuation planning was inadequate.

Organizational aspects of flood warning dissemination

There are multiple communication channels by which a flood warning may be broadcast and the choice of media will vary depending on the intended recipients. It is also essential to consider the use of media that will be robust to the impacts of a flood.

The most successful warning services use a combination of media, ideally with consistent messages and timescales, as well as the response the message hopes to initiate. For example, an individuals whose home is likely to be flooded will probably react best to a personal message either via phone, fax or in person; people who should avoid travelling to or through an affected area may prefer a news bulletin backed up by an internet or press map of the affected area.

Costs and resources

Setting up a warning system may be a low cost option for countries and is often seen as the first line of defense for that reason. The cost will be lowest in nations with existing and adequate forecasting and monitoring services. In this case the setting up of a warning center can be a very low cost process and this can be quickly established during consultation and stakeholder identification.

Setting up adequate forecasting and monitoring serviced can require much larger investments in expertise, software and hardware for modeling and monitoring equipment. The lead time to establish forecasts of the required reliability and timeliness may be a deterrent.

Key lessons learnt

Once established the service will require continuous investment in manpower, data and other resources in order to be functionally useful. Recruitment and retention of qualified personnel, continuity of funds and operations and maintenance of monitoring, modeling and dissemination equipment can be key challenges in the long term sustainability of systems. This can be particularly acute for low frequency events.

Relevant case studies and examples

EXAMPLE: Early warning system in Sogn og Fjordane (NOR)

Literature sources

United Nations. 2006. Global survey of early warning systems. UN.

Measure category

Preparedness

Emergency planning

giacomo.cazzola — Thu, 15 Sep 2016 10:47:05 +0000

Emergency planning giacomo.cazzola Thu, 09/15/2016 - 12:47

Riverine or slow rise floods

Flash floods

Estuarine floods

Coastal floods or storm surges

Urban floods

Emergency Event and Contingency Planning

Non-structural measure

It is vital to recognize that even after the implementation of non-structural flood mitigation measures residual flood risk will remain. It is of paramount importance to make plans to deal with flood events and their aftermath. This involves multiple activities which can be included as part of a flood emergency plan. In this section there is an overview of the elements central to emergency planning.

Based on: Jha, Abhas K., Robin Bloch, and Jessica Lamond. Cities and Flooding: A Guide to Integrated Urban Flood Risk Management for the 21st Century. World Bank Publications, 2012.

Identifying existing internal organizations

All countries possess existing institutions and organizations that, if coordinated, may be mobilized to meet individual emergencies. The purpose of the emergency plan is to identify these institutions prior to the emergency in order to:

Identify roles and responsibilities.
Identify command structures.
Facilitate inter-agency cooperation.

The preparation of the emergency plan will help to identify barriers to cooperation, including authority structure and finance, which need to be resolved before flooding occurs.

Identifying appropriate external agencies

Some flooding events may be addressed using existing national resources but many countries do not have sufficient physical and human resources to address regional and national emergencies. It would then be appropriate to invite the assistance of external agencies.

The presence of international agencies may, however, overwhelm the host government with the risk that the latter may lose control of the relief effort. This, in turn, can result in the deskilling of local people who may feel it necessary to defer to the external agencies. It should also be recognized that the objectives of external agencies may conflict with those of internal agencies: for example, to ‘showcase’ their charity in high profile emergencies. Managing these agencies is both difficult and time consuming and may require considerable diplomacy.

The emergency plan should therefore contain detailed policies, identifying the roles and responsibilities and restrictions on invited agencies.

Damage Avoidance

Actions taken before a flood arrives can significantly reduce the loss of life and the amount of damage suffered. Pre-warning and evacuation planning should therefore be part of an emergency plan. It follows that an early warning system (see Section 4.9) is a central requirement for damage avoidance. Local flood emergency planning could involve, for example, the installation of temporary flood barriers, or the removal of zoo animals (as in the Cologne case study elsewhere in this volume). Deployment of some building design features, as described in Chapter 3, may also be dependent on warnings being issued.

It is necessary to mobilize personnel and machinery, where available, to protect infrastructure (such as dikes, levees and retention basins); to remove individuals from facilities at risk (such as hospitals, schools, industrial sites, bridges, or individual houses); and to prevent landslides and riverbank erosion. Strengthening and rehabilitation of existing structures and flood-proofing measures can also protect critical infrastructure. Such measures may include sandbagging or establishing temporary earth, wooden or other flood barriers, including mobile flood barriers (WMO 2011).

Flood emergency preparedness activities

To coordinate emergency procedures, a flood management unit (FMU) needs to be set up. Representatives from the local community should be included as members. The FMU will be responsible for developing a business and government continuity plan (BGCP) and for coordinating emergency procedures in a secure flood free location, as identified in the evacuation plan. The FMU can also be organized to serve as the local representative, focal point or community partner for wider river-basin level planning. Government continuity planning requires the community to effectively participate throughout the planning process. Participatory planning for emergency situations can help build trust and confidence among stakeholders, enhance cooperation, facilitate information sharing and encourage regular communication (WMO 2011).

At a household level a number of strategies can be adopted which will reduce damage as a result of flooding. Including the following:

The identification of household escape routes
Installation of temporary flood proofing
The identification of elevated buildings (or even mature trees) that can be used as safe havens
The moving of property to higher levels
The storing of emergency provisions
The use of non-flood impacted communications such as radios, mobile phones or even prearranged signals in order to share information
The removal of vehicles from the area: their use in the post-flood situation is invaluable.

Emergency water supplies and sanitation

The flooding will have destroyed existing water supplies and sanitation infrastructure, where applicable; any overflow of sewage will also have polluted water supplies. The emergency plan should therefore identify alternative water supplies, preferably gravity-fed to avoid the need for pumping. The tankering of water is a very short-term solution which uses vehicles and fuel which could be more beneficially employed elsewhere.

Similarly, sanitation should be provided close to the displaced population, away from the source of water supply and on unsaturated permeable strata to allow sufficient drainage. These factors should be taken into account when locating refuges and other areas of residence.

Access

Flooding may affect both roads leading to the flooded area as well as those within it. This can include blockages of debris and silt, as well as flooding or washing away.

The emergency plan should therefore identify the following:

Access roads to and within the flood zone, avoiding low bridges over rivers, low- lying areas, roads susceptible to land slippage (in cases of flooding caused by heavy precipitation) and highlighting those not susceptible to crime and insecurity.
The design and location of permanent signage on principal road routes.

The use of symbols avoids the difficulties of literacy and language.

Suitability of road, railways and airfields, where available, for longer distance transport of supplies.
Suitability of ports near main shipping lanes, with sufficient depth and with suitable loading and unloading facilities for international vessels.

Clearance

Floods deposit large volumes of debris and mud, the clearance of which is essential for the relief effort. The emergency plan should identify how the debris and mud is to be cleared, by whom and where is to be deposited.

Emergency health facilities

Flooding may generate a range of injuries. The emergency plan should identify:

The suitability of public buildings to act as preliminary treatment centers (such as schools, government offices or similar).
Existing hospital facilities, away from the likely flood area, that may be developed with specialist services and equipment.
The method of evacuation for those with more serious injuries.
A system of vaccination.
The suitability of public areas (such as parks and schools), for the siting of mobile clinics units, temporary camps and distribution centers.
The provision of power, as electricity supplies (where these exist) are likely to have been severed.

Energy

It is likely that the floods will destroy access to energy resources, be they electricity or, in less developed areas, other forms of fuel including wood and animal dung. The emergency plan should identify:

The local fuel resources and their continued accessibility during and after a flood.
Alternative sources of energy (for example, generators) and the fuel to run them.
Key institutions such as hospitals which should be supplied with these alternative sources and the methodology for ensuring their continued availability between floods.

Security

Emergency situations, and the breakdown of the normal standards of society and their enforcement, often create opportunities for theft and corruption.

The emergency plan should therefore include:

The securing of the facilities identified in the emergency plan, between and during flood events.
The visible deployment of reliable security forces immediately post flood to deter looting.
External auditing of government functions for efficiency and probity.

Key lessons learnt

An appropriate and implementable emergency plan can:

Facilitate emergency response.
Minimize the impacts of flooding.
Allocate resources efficiently.
Reduce confusion.
Facilitate recovery.

Literature sources

WMO. 2011. Flood Emergency Planning: A tool for Integrated Flood Management. Associated Program on Flood Management.

Measure category

Preparedness