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Competence Network Climate Change, Risk Management and Transformation in Forest Ecosystems

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Forest Research Institut Baden-Württemberg (FVA)
Department of forest economics

Wonnhaldestr. 4
D-79100 Freiburg

Tel:  +49 761 4018 231
Fax: +49 761 4018 333

Article

Author(s): Jutta Odenthal-Kahabka
Editorial office: FVA, Germany
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Survey of Damages after Storm Events

Click here to download the Spanish translation (PDF-file)
 
Sturmfläche
How many solid cubic meters of timber have been thrown?

Exact information on the extent of storm damage experienced by forest owners is important to forestry offices/ forest authorities, forest districts as well as for forest administration management planning, organising and coping with the storm’s aftermath.

The surveyed figures are not only useful for the enterprises but also for administrations controlling the timber market or the establishment of support programs for strongly affected enterprises.

Experiences in the wake of storms "Wiebke" and "Vivian" in 1990 have shown that the preference for an exact survey of many parameters in the first days after a storm puts too much pressure on forest enterprise personnel, especially personnel of seriously damaged enterprises. The onset of winter with frost and snow following winter storms leads to further delays in reporting of damages. However, authorities can't control storm recovery activities properly, if exact figures don’t follow the rough estimation of damages.

Therefore a two-stage process is proposed, where a rough survey of damages takes place in the first days after the storm and a more detailed estimate of the amount of storm-damaged timber is made in the following weeks and figures are improved and updated.

  1. Rough survey of the amount of storm damaged timber
  2. Exact survey of the amount of storm damaged timber / damages

Rough survey of storm damaged timber (within the first 24 hours)

Objectives of the rough survey:

  • Overview of size and extent of storm damages, i.e. amount of storm damaged timber and windthrown area
  • nformation to policy makers to initiate supporting measures / relief programs (e.g. subsidy program, ordinance to the forest damage compensation law)
  • Information of public (PR)
  • First informational basis for coping with storm damages, definition of strategy (logging stop, first adjustments between work volume and work capacity as well as storage capacity)

Parameters to be collected at the forest district level during the rough survey:

  • Timber quantity in solid cubic meters total and separated in hard / soft wood as well as forest owners, as far as possible
  • Area damaged in ha

Report of figures within 24 hours after event to:

Baden-Wuerttemberg Rheinland-Pfalz
Rural district forestry offices Forestry offices

Who gather the reports and forward them to

Departments of Forestry at the Regional Administrative Authority in Freiburg and Tübingen (Dept. 8) Struktur- und Genehmigungs­direktion Süd, Center of State Forest Administration (ZdF), Neustadt a. d. W.
as well as to
Department of State Forest Administration at the Ministry of Nutrition and Rural Areas Department of State Forest Administration at the Ministry of Environment and Forest

The first rough surveys of damages / damaged timber are just estimations due to the urgency of immediate recovery measures (assistance, clearing of roads), which do not leave much time for surveys. Experiences after "Lothar" have shown that long serving forest rangers can estimate the situation relatively well. Although a delay in first estimations is possible, due to serious damages and corresponding workload, a rough estimation from forest management data is helpful. The stand volume (cubic meters standing) and area allow a rough estimation of the damages.

For non-accessible or non-visible areas it may be possible to get an overview by helicopter.

Exact survey of storm damaged timber / damages (detailed inventory)

Objectives of the exact survey:

  • The exact survey helps on-site personnel to plan the processing of storm damaged timber. Therefore it’s important to survey, in addition to the amount of damaged timber and the dimension of the affected area, further parameters for every storm area including tree species, type of damage (area damage/single throws, breakage/throw), terrain and urgency of processing (e.g. valuable assortments, forest protection situation, opening-up).

Parameters to be surveyed at detailed inventory of damaged area stage:

- Amount of timber in solid cubic meters per damaged area, separated into tree species

- Expected assortments

- Area damaged in ha

- Type of damage

- Terrain and opening-up (roads etc.)

- Forest protection situation, urgency of processing

- Type of processing

- Contractors / own labour

- Capacity requirement

- Miscellaneous (regeneration, harvesting methods, application of technique)

  • Detailed planning further approaches and measures to cope with storm damages and determining strategies (order of processing and method, assortments, kind of storage and storage possibilities, effects on the timber market or sale price as well as predictions of subsequent forest protection problems) at both the forest district and management/federal state level.
  • Information for policy makers to initiate supporting measures / relief programs (e.g. support program, ordinance to the forest damage compensation law)

It has been found helpful to mark the storm areas on ranger district maps showing the extent and amount of storm damaged timber (e.g. basic forest map with a scale of 1:10 000). Furthermore it’s possible to mark storage areas and conversion sites on the maps.

Application of helicopters / small planes and remote sensing data

Besides the necessary terrestrial survey and estimation of damages by forest enterprise personnel in the first days after the event, which is very important for further internal approaches, surveys by helicopters (or small planes) can be helpful,

  • to gain a overall impression of the situation
  • to survey damages at remote or non or difficult to access forest areas (e.g. plateaus, large areas)

Preparation of flights - requirements and measures

  • For a contemporary aerial survey the assistance of other administrations (e.g. police) should be sought, but private flight can also be chartered.
  • Allow sufficient time to fly over forest districts as well as damaged areas and to survey several areas in more detailed.
  • Flights have to be prepared by forestry office personnel in advance. It’s more efficient and allows for important areas to be surveyed in detail, if the flight route is defined before take-off.
  • Cameras and/or video cameras should be used to document the storm damaged areas. Experience proved that photos or videotapes, which can be evaluated afterwards, are helpful for further planning.
  • Basic forest maps with a scale of 1:25 000 or older aerial photographs are helpful for orientation. Damaged areas can be marked on the maps/photographs.

The use of flights for an exact mapping or survey of damages is restricted as there is less time for precise orientation, it is difficult to delimitate areas on a map and single throws are difficult to identify or not visible at all.

Aerial surveying doesn’t replace terrestrial inspections, but complements them. Flights provide an overview of the situation and have a powerful psychological and emotional effect on those who can’t get into the forests. Flights can bridge information gaps if a fast survey with remote sensing is not possible (see below).

Remote sensing

Results of the project "Sturmmon" by the University of Freiburg, Department of Remote Sensing and Land Information Systems (Issue 2003):

Storm event in winter Storm event in summer
Initial position
  • Low altitude of the sun, i.e. larger shadows, primarily mountainous terrain (e.g. Black Forest, Swabian Mountains, Palatinate Forest)
  • Areas with snow (low mountain range)
  • Longer spells of bad weather after storm event, which makes the application of remote sensors difficult
  • Possibility of confusion between deciduous forests and possible storm damaged areas
  • High altitude of sun, more suitable for surveying
  • No snow
  • Less spells of bad weather than during winter
  • Foliated deciduous forests reduces possibilities of confusion with storm damaged areas
Fast survey of damages Present:
  • Airborne radar (X-, L-Band) recording of coherence data. High areal resolution (1-2 m). Recoding of "hot spots" (pictures of important areas)

Future:

  • Analysis of satellite-borne radar data (TerraSAR, Radarsat-2)
Present:
  • High altitude flight aerial photograph, flight scale of 1:40 000, if possible colour infrared film. Essential: immediate flight and fast improvement in weather conditions
  • Airborne radar(X-, L-Band) recording of coherence data. High areal resolution (1-2 m). Recording of “hot spots” (pictures of important areas)

  • Limited (lead time): combination of Landsat TM multi-spectral and IRS-1C pan­chromatic
  • SPOT 5 multi-spectral (for mapping Pan-data as well) Immediate order is necessary to receive data quickly.

Future:

  • Analysis of satellite-borne radar data (TerraSAR, Radarsat-2)
  • RapidEye
Survey and mapping of damages Present:
  • High altitude flight aerial photograph, flight scale of 1:40 000, if possible colour infrared film.
  • Combination of multi-spectral SPOT 5-data with SPOT 5 panchromatic; data with an areal resolution of 5 x 5 m, improved 2,5 x 2,5 m

Future:

  • SPOT 5, see above.
  • RapidEye
Present:
  • High altitude flight aerial photograph, flight scale of 1:40 000, if possible colour infrared film.
  • Combination of multi-spectral SPOT 5-data with SPOT 5 panchromatic; data with an areal resolution of 5 x 5 m, improved 2,5 x 2,5 m. Immediate order of data is necessary.

Future:

  • SPOT 5 multi-spectral und panchromatic (see above)
  • RapidEye

Literature

  • Landesforstverwaltung Baden-Württemberg (Hrsg.): Schriftenreihe der Landesforstverwaltung, Baden-Württemberg Bd. 83: Orkan "Lothar" – Bewältigung der Sturmschäden in den Wäldern Baden-Württembergs, S. 113-123.
  • Steinmeier, C.; Schwarz, M.; Holecz, F.; Stebler, O.; Wagner, S., (2002): Evaluation moderner Fernerkundungsmethoden zur Sturmschadenerkennung im Wald. Birmensdorf, Eidg. Forschungsanstalt WSL. 194 S.

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