The restoration of sediment-related disasters and driftwood from national forest in caused by Typhoon Morakot in 2009

Su Chin Chen *, Jau Pao Wang **, Chun Hsien Yang ** Department of Soil and Water Conservation, National Chung Hsing University* Forestry Bureau, Council of Agriculture, Executive Yuan**

ABSTRACT: The number and area of new landslide, according to the interpreted SPOT images, caused by Typhoon Morakot in 2009 is estimated as 30,223 and 43,996 ha, respectively. The new landslide area in 2009 increased by about 16,392 ha in comparison with the landslide area in 2008. The heavy rainfall with a return period well over 200 years during Typhoon Morakot centralized in southwestern and southeastern Taiwan, and that also resulted in serious landslide disasters in national forest. Four forest working circles, including Chishan, Laonong, Pintung, and Dawu, are the most serious landslide zones with the landslide ratio over 8.0%. The Forestry Bureau assesses and ranks the seriousness of the disasters by using slope, the number of protected objects, the distance from the disaster to the protected objects to execute the restoration of sediment disasters and landslide in national forest. Due to the most torrential rain in the past 50 years caused by Typhoon Morakot, a large number of trees in the mountain area were destroyed. They became the driftwood, with a total weight of about 1.52 million tons, which ended up at the farmlands and ports. In order to recover agricultural products and livelihoods, Forestry Bureau made strategy for disaster prevention and reduction. Based on the strategy, Forestry Bureau sweeps away the driftwood by estimating its distribution, overcomes the issues caused by the heavy rainfall disaster, and helps the victims to recover their life.

KEYWORDS: Sediment-related disaster; Landslide; Driftwood

- 1 - 1. Introduction 22,696 ha to 48,605 ha after the typhoon, indicating a new landslide area of 25,909 hectares. The rapid global climate changes are causing Landslide survey work performed subsequently in intensive typhoons and torrential rainfall into 2010 and 2011 found that the area affected by normalization. Taiwan's national forests are landslides on land under the jurisdiction of the mainly covered by forest vegetation and can four forest offices was 33,333 ha at the end reduce soil erosion in the normal condition. of 2010 and 25,015 hectares at the end of 2011. However, when continuous rainfall in a single Figure 1 shows the scope of landslide survey work 24-hour period exceeds 400 mm, forest land in the Zhuoshui River District on a satellite image could become extremely prone to landslides. In taken by FSAT-2. The areas of landslides in the addition, rock, soil, and wood carried by remaining forest districts were obtained using the landslides often cause sediment-related same method. disasters and massive deposits of woody debris. According to the results of these landslide surveys, When Typhoon Morakot struck Taiwan in the Typhoon Morakot indeed caused a large August 2009, rainfall exceeding 2,000 mm in number of landslides on national forest land under many areas overloaded the capacity of forest the jurisdiction of the Forestry Bureau's Nantou, vegetation, causing large numbers of landslides Chiayi, Pingtung, and Taitung forest district on national forest land. These landslides carried offices. According to landslide survey data in 2011, massive amounts of soil, and wood from owing to the absence typhoons and torrential slopeland forests borne along with the soil in rainfall during that year, initial vegetation had the torrents caused by heavy rainfall yielded an begun growing on landslide areas, and natural unprecedented 1.52 million tons of woody restoration was consequently beginning. The debris, giving forestry personnel a severe Forestry Bureau is performing surveys. challenge.

2. Landslides in National Forests

Following the Typhoon Morakot, images taken in cloudless weather by the FORMOSAT-2 (FSAT-2) satellite from August 8 to October 31 were used to determine the damage caused by the typhoon. After determining the area of land affected by landslides in areas under the jurisdiction of the Nantou, Chiayi, Pingtung, and Taitung forest district offices in the wake of Typhoon Morakot, the Forestry Bureau Aerial Survey Office found that the area of landslides increased from 13,786 hectares to Fig. 1 Satellite photograph and scope of landslide survey-Example of the Zhuoshui River District 32,923 ha after the typhoon, which indicated that new landslides had affected an area of 3. Planning of Sediment Related-disaster 19,137 ha. In addition, for all of Taiwan, the Mitigation in National Forest Land area affected by landslides increased from Most national forest land in Taiwan is located - 2 - along the Central Mountain Range, so the terrain remediation, and status of the remaining 142 is steep and streams are short and fast-running. As sub-watersheds was designated as a consequence, and also because of the fragile sub-watershed in need of remediation. In geology, landslides are a natural phenomenon. addition, a total of 25 sub-watersheds within Because whether landslide areas require the experimental forests of National Taiwan remediation work must be assessed, the Forestry University and National Chung Hsing Bureau commissioned the use of satellite images University were assessed as sub-watersheds to determine whether such factors as the rainfall, requiring highest-priority remediation, hydrology, ecological environment, preservation giving a total of 167 sub-watersheds objects, relief ratio, geology, vegetation coverage, requiring highest-priority remediation; soil erosion, landslide ratio, debris flow torrents, survey, planning, and river training works flow section, historical disasters, land use, and for these sub-watersheds will be completed various river training works within watersheds as part of a mid-term plan (2012-2016) will affect the incidence and scope of flooding, (Table 1). landslides, and debris flow. Taking national forest 3.2 Sub-watersheds in need of remediation: watersheds as the subject of assessment, the seven Sub-watersheds in need of remediation may assessment indicators of preservation objects, have a weighted score of at least 55 points, relief ratio, geology, vegetation coverage, soil implying that they should be assessed as erosion, landslide ratio, and debris flow torrents, sub-watersheds requiring highest-priority as well as the foregoing assessment indicators, remediation, but have few points from were used to determine finer assessment items and preservation objects, contain a wildlife scoring standards, allowing the assessment of the refuge, or contain no roads, or have a have a risk of national forest sub-watersheds and scoring. weighted score of less than 55 points, and The scores of different sub-watersheds were used are therefore considered to have a status of to determine the priority order of remediation key remediation or general remediation work in national forest sub-watersheds, yielding sub-watersheds; however, if there are many the following results: points from preservation objects, a 3.1 Sub-watersheds requiring highest-priority sub-watershed's remediation priority shall be remediation: Those sub-watersheds on the designated rolling management, which foregoing assessment table are considered to implies that the Forest District Office with require highest-priority remediation if they jurisdiction shall perform remediation have a total weighted score of at least 55 according to need (Table 1). points. A total of 295 sub-watersheds were 3.3 Key remediation sub-watersheds: The key assessed as having scores of at least 55 remediation sub-watersheds listed on the points. However, if a sub-watershed had few foregoing assessment table have a weighted points from preservation objects, contains a score of from 55 to 50 points, and it is wildlife refuge, or contains no roads, its expected that survey and planning work will status was changed to a sub-watershed in be completed within ten years as part of need of remediation. Following assessment, long-term plans (Table 1). the status of 153 sub-watersheds was 3.4 General remediation sub-watersheds: All changed to sub-watershed in need of general remediation sub-watersheds on the

- 3 - foregoing assessment table have this status. construction, the remediation of These sub-watersheds have a weighted score upstream watershed areas in national of less than 50 points; their status may be forests will generally focus on achieving adjusted in the future as their situation stability and control, and watersheds will changes (Table 1). be taken as the unit of remediation. Assessment will be performed on the basis of watersheds' preservation objects, Sub- wate relief ratio, geology, vegetation coverage, rshe Sub- Gen Key ds wate eral rem Tota soil erosion, landslide ratio, and streams requ rshe rem edia l iring d in edia tion (sub with debris flow potential, and the high need tion sub- -wat est- of sub- Management wate ersh determination of remediation priority prio rem wate office rshe eds) rity edia rshe will also reflect current watershed status, d rem tion ds edia including landslide survey results, past tion landslides, and state of remediation. Hsinchu office 10 16 5 69 100 Remediation work items include source Dongshi office 13 48 13 74 148

Nantou office 21 48 24 64 157 remediation, landslide remediation,

Chiayi office 43 40 14 38 135 torrent remediation, sediment control

Pingtung office 42 89 8 35 174 facilities, emergency disaster

Taitung office 3 38 3 12 56 remediation measures, and revetments

Hualien office 6 16 2 8 32 and retaining facilities, etc. From a

Luodong office 4 28 2 18 52 perspective of ecology engineering, the National Taiwan planning of watershed remediation work University 19 3 4 4 30 experimental aimed at achieving water and soil forest National Chung conservation will take function, safety, Hsing University 6 1 - - 7 ecology, and environmental scenery into experimental forest consideration. Total (sub-watersheds 167 327 75 322 891 4.1.2 Appropriate sediment control ) Table 1 National forest sub-watershed facilities will be adopted as remediation remediation status distribution table measures addressing various changes in torrents, and will seek to stabilize and 4. Landslide Countermeasure in National control the riverbed, prevent or mitigate forest Land torrent erosion, scouring, and bank 4.1 Remediation strategies: Within the overall landslides, stabilize gullies, prevent the disaster survey and planning design, survey, expansion of erosion, effectively control and monitoring will be performed on the sediment production and transport, and ecological environment and landslides in reduce scouring and bank landslides. national forest watersheds, and overall Project implementation planning and remediation planning work will be design will take ecological conservation, conducted to provide a basis for river the project as a whole, the content of the training works. planning report, and landslide severity 4.1.1 With regard to watershed into consideration, and will be followed management and erosion control project - 4 - by approval of the project and project existing national forests structures have control. River training works will include been damaged, reinforcing or repair sediment control measures include slope work will be performed. Furthermore, stabilization, ground sills, and emergency clearing or remediation will revetments intended to curb the downhill be performed at places where new transport of soil, maintain the stability of landslides have occurred. With regard to longitudinal slopes, control scouring follow-up maintenance, forest district threatening the stability of forest areas, offices will regularly patrol completed and prevent secondary landslides, watershed management, erosion control, achieving stream stabilization, gully and restoration projects, and will perform control, torrent control, and debris flow maintenance work when necessary to prevention and control. maintain the projects' functionality. 4.1.3 Precipitous exposed slopes, fracture zones, landslide scars, slippage zones, and other areas where revegetation and reforestation are unlikely to be successful will be handled through the use of foundation Fig2.1 Before removal of sediment from Toukeng Creek in Xinyi engineering for exposed ground, along , with supplementary revegetation of landslide scars and drainage works. Apart from seeking to stabilize the landslide foundation and prevent

secondary landslides, revegetation and Fig2.2 After the removal of drainage projects can also inhibit slope sediment from Toukeng Creek in landslides due to scouring from Xinyi Township, Nantou County concentrated rainfall or runoff. 4.1.4 With regard to emergency remediation and maintenance projects, because sediment from torrents on national forests land may severely Fig2.3 Before emergency sediment removal from forest compartments 52 obstruct flood drainage, threatening & 53 in the Yujing District, Dapu roads, bridges, public facilities, and Township, public safety, emergency remediation projects will be implemented on an expedited basis. These emergency projects will clear accumulated sediment Fig2.4 After emergency sediment from stream beds, eliminate channel removal from forest compartments 52 blockage, restore flood drainage ability, & 53 in the Yujing District, Dapu and reduce and mitigate soil loss caused Township, Chiayi County by typhoons and torrential rains. Where

- 5 - Article 15, Paragraph 5 of the Forestry Act states: "Following a natural disaster, when bamboo and wood is carried from a national forest to outside the national forest, the local government must complete recording of clean-up within one Fig2.5 Landslide remediation month; if a local government fails to complete project in forest compartment 39 near the Qishan River recording of clean-up within one month, local residents may freely collect and remove the material." Accordingly, in order to clean up woody debris resulting from natural disasters and implement the drifting object clean-up response measures in Article 27, Subparagraph 14 of the Disaster Prevention and Response Act, on July 4, Fig2.6 Completed lateral and 2005 the Taiwan Forestry Bureau, Council of longitudinal drainage project on landslide scar at 5K on Tengzhi Agriculture called together relevant agencies and Forest Road. local governments for the purpose of determining 4.1.5 Remediation results: In the wake the "Guidelines for the Clean-up of Woody Debris of Typhoon Morakot, funds from the Resulting from Natural Disasters," which Special Budget for Reconstruction after prescribe that the management agency or industry Typhoon Morakot were used between competent authority with local jurisdiction shall 2010 and the end of 2011 to implement bear responsibility clean-up of woody debris, and 103 national forest watershed establish a division of labor and standard management and erosion control operating procedures. The Guidelines have been (watershed management and erosion forwarded to relevant agencies for implementation, control/hillside stabilization) and there are mechanisms for annual review and reconstruction projects. These projects revision based on practical needs. Substantive stabilized landslides covering 194 ha, rounds of review and revision were performed on controlled the erosion of 5.25 million June 21, 2007; July 14, 2009; May 20 and cubic meters of soil, and mitigated November 30, 2010; and June 27, 2011; see Table landslide dams on the Taimali River 2 for the assignment of responsibilities. (Taitung office), and Qishan River (Pingtung office), and Shiwen River Location Responsible unit (Pingtung office). The projects National forest Within national forests preliminarily achieved national forest management agencies Reservoir management watershed management and erosion Reservoirs agencies (organizations) control goals; subsequent work will be Emergency clean-up: performed with funding from relevant River bureaus under the project budgets. Figure 2 shows the Water Resources Centrally-man Agency, MOEA Rivers results of sub-watershed remediation aged rivers Non-emergency work in national forests. clean-up: special municipality, county 5. Clean-up of woody debris (city) governments

- 6 - Rivers Special municipality, thinking. The use of all possible methods in the managed by county (city) clean-up campaign underscored the government's cities and governments counties active, responsible attitude and sought to restore Weir management Weirs farming and production while the problems faced agencies by affected residents. In view of the distribution of General Irrigation facilities Seawa seawalls competent authority woody debris during the disaster relief period, the lls Industry-type Industry competent Forestry Bureau, Council of Agriculture (COA) seawall authority consequently drafted the following strategies as Registered as Forest District Office, a shelter part of the "Treatment Principles for Woody Forestry Bureau forest Debris Resulting from Typhoon Morakot": Registered as 5.1 Woody debris in fishing harbors under management The first priority consisted of the National Property of the Bureau clean-up of navigation channels, followed Beach National (shore Property by clean-up of entire harbors. A total of ) Bureau 52 fishing harbors clogged with woody Designated a Scenic area debris were distributed in 10 cities and scenic area management office Designated a National park counties, and included such major fishing national park management office harbors as Fugang in and Non-registere County or city in . Working 12 d land government hours a day, navigation channels were Commercial port Commercial port management agency cleared by August 18, enabling fishermen Fishing harbor Fishing harbor to get to fishing and restoring the management agency transport of supplies to Lanyu and Green Public or private enterprise with Ministry Island by ship. All woody debris was of Economic Affairs subsequently removed from fishing Industrial port approval to invest in construction and harbors, and any woody debris that floats management of into a harbor from offshore is promptly industrial port removed (Fig 3.1). Military port, military Military port beach management agency 5.2 Woody debris on farmland Special municipality, Because of the failure of major dikes, county (city) much woody debris was deposited on government; when Private land (farmland) necessary, assistance farmland. More than a thousand hectares may be requested from a of farmland in the -Pingtung Forestry Bureau forest district office. area was covered with woody debris, and TABLE 2 UNITS ASSIGNED RESPONSIBILITY FOR the situation was particularly severe in CLEAN-UP OF WOODY DEBRIS RESULTING FROM Jiuru, , Wandan, Daliao, and NATURAL DISASTERS Qishan townships. This woody debris had Because the August 8, 2009 typhoon generated to be removed as quickly as possible in an unprecedented volume of woody debris, the order to restore farming. In this type of clean-up process could not be limited to existing situation, past operating procedures guidelines or procedures, but required the called for Forestry Bureau personnel to incorporation of disaster relief and mitigation

- 7 - first record the presence of any valuable Clearing Woody Debris Resulting from wood and then remove all woody debris. Typhoon Morakot from Farmland," In the wake of Typhoon Morakot, which provided a subsidy of NT$10,000 however, all woody debris was removed, per hectare to affected farmers clearing regardless of whether it contained their own land. valuable wood that could be sold at 5.3 Woody debris in rivers auction, and piled at storage yards; the According to Article 76 of the Water wood was then recorded and subsequent Utilization Act, the river management handling procedures implemented (Fig agency must remove any woody debris 3.2). threatening river control on an emergency Early announcement of free collection basis. Based on the fact that large and free use by private companies: After amounts of woody debris were deposited Forestry Bureau personnel complete in riverbeds by Typhoon Morakot, and recording any valuable wood, following the Water Resources Agency undertook the one-month deadline prescribed in many river management reconstruction theForestry Act, it can be announced that and dredging projects in the wake of the citizens could freely collect any typhoon, the Water Resources Agency unrecorded wood. In the case of Typhoon also removed woody debris when Morakot, after Forestry Bureau personnel implementing these projects or clearing recorded valuable wood on an expedited sediment. Town and township public basis, early announcements were made of offers were assigned to clean up woody free public collection. Kaohsiung and debris lying in riverside areas after joint Pingtung counties announced free surveys by river bureaus, city and county collection on August 15, and Taitung governments, and forest district offices County made such an announcement on (Fig 3.3 & 3.4). August 20. In addition, apart from the 5.4 Woody debris in coastal areas early announcement of free collection, it The government called on county and was also announced on August 30 that city governments, land management private companies and manufacturers agencies, and industry competent could freely remove wood of any size authorities to clean up coastal woody from areas designated by the local forest debris, and made an early announcement district office and could use the wood and of free collection. Encouragement of woody debris in the manufacture of beach clean-up by volunteers: Because of compost, pulp, or other items. All the vast amounts of woody debris that interested companies were allowed to call washed up on beaches, the government the local forest district number for mobilized volunteers to clean up beaches, permission. and the Environmental Protection Government subsidies encouraging Administration charged local farmers to clear their own land: The environmental protection bureaus to Forestry Bureau drafted the "Budget assist with transport and disposal. Measure for Subsidies to Farmers 5.5 Woody debris at sea

- 8 - With regard to woody debris at sea construction and 2,000 tons of woody resulting from Typhoon Morakot, because debris subsequent village reconstruction it had been announced that citizens could projects. In addition, the Chant Oil Co., freely collect debris from affected areas, Ltd. donated NT$1 million specifically to fishermen were also allowed to freely assist Jialan Village construct salvage wood. In accordance with the demonstration homes and for the facts, the ownership of such wood was transport of woody debris and purchase handled in accordance with Article 802 of of other building materials needed in the the Civil Code, which prescribes finders' construction of a village meeting house. rights to ownerless property, or Article The company also worked together with 810, which specifies the regulations the Taitung County governments and concerning the collection of drifting Jialan Village during the reconstruction objects. period to plan and design demonstration 5.6 Diversified use of woody debris homes and the meeting house. By Usable wood combining the wisdom of Paiwan and In accordance with the "Guidelines for the Rukai elders with modern architecture Clean-up of Woody Debris Resulting from and flexible applications, this campaign Natural Disasters," woody debris resulting created village homes and a meeting from natural disasters may be auctioned house with an indigenous character, while when determined to have auction value by expressing the traditional harmony the forestry competent authority. between Taiwan's indigenous cultures and the natural world. Based on the experience acquired in the construction of 6. Diversified utilization demonstration homes, this Bureau Apart from small amounts of valuable wood continued to assist with the such as red cypress, yellow cypress, and reconstruction of homes in other camphorwood, which could be sold at auction, the indigenous villages, and established woody debris produced by the Typhoon Morakot architectural design drawing and standard consisted mostly of battered logs and scrap from construction process teams needed for trees with no particular commercial value. But subsequent home reconstruction work. although this wood lacked sufficient value for sale 6.2 To assess the application of woody debris at auction, it could still be used for making to the generation of biomass energy, furniture or pallets, as mushroom growth medium, Forestry Bureau held a conference with boiler fuel, landscaping articles, or a sculpture the Environmental Protection medium. In view of these circumstances, the Administration to discuss the use of Forestry Bureau devised the following strategies refuse derived fuel (RDF) and the to promote the diversified use of woody debris: feasibility of producing RDF from woody 6.1 Village reconstruction debris. At this conference, companies The Bureau's Taitung district office expressed that, because of current process, provided the affected Jialan Village with technological, and financial difficulties, 140 tons of wood needed for home as well as sales issues, this concept is not

- 9 - feasible at present. In addition, the and foreign artists (including those from Bureau also commissioned National Japan, Korea, Canada, and Chung Hhing University to study the disaster-stricken areas in Taiwan) to economic performance of a wood jointly produce art giving the driftwood a gasification system. This research found new purpose. that, as an example, a gasification furnace The Forestry Bureau commissioned the generating 5 million W in thermal energy Chinese Forest Products Association to would have a high power generation cost hold the "Woody Debris Diversified of NT$2.46 per kWh, and would require Utilization Plan and Forestry 8,100 tons of biomass annually. Since the Conservation Awareness Activity" and power generation cost of this system offer a wood carving training class would be higher than the wholesale cost providing training to 90 residents of of NT$2.0615 per kWh for biomass disaster-stricken areas. The "Language of energy in Taiwan during 2010, it would Wood" driftwood carving contest held on not be economically efficient. July 25, 2010 showed how woody debris 6.3 Driftwood carving art could be given greater reuse value. A The Forestry Bureau joined forces with woody debris diversified utilization and Taipei National University of the Arts and creative design paper and results other organizations to hold the announcement conference held on International Driftwood Sculpture November 16, 2010 featured talks on Festival at Guandu. Twelve foreign and woody debris utilization technologies and domestic teams of artists were invited to product design approaches by speakers create works of art from driftwood from academia and industry, and washed and scoured by the forces of provided ideas for enhancing the value of nature. The artists produced 13 large woody debris. works, including "Prayers for Blessings Advanced high-temperature to Living Beings," "Devotion," and carbonization technology was used to "Reflections on Driftwood." These works transform woody debris into ecological were displayed on Taipei National charcoal used for deodorization, moisture University of the Arts' Egret Lawn adjustment, soil improvement, and water (Fig3.5to 3.8). purification. The charcoal was also The Forestry Bureau also teamed up with cleverly used as a creative material in the Council for Cultural Affairs and installation art, showing how this Taitung County government to jointly material combines everyday life and art. hold a series of activities forming the In order to make the best use of woody 2009 East Coast Driftwood Art debris resulting from Typhoon Morakot, Exhibition. These activities included a employing NT$10 million donated by the driftwood art activity, driftwood carving Chant Oil Company, the Forestry Bureau activity, photography contest, and the and Qinghua Online Cultural & invitation of domestic master wood Educational Foundation jointly carver Wu Hsuan-san and other domestic implemented the "Plan to Use of Woody

- 10 - Debris in the Development of Indigenous it was created, it can be used to create new kinds Cultural and Creative Industries in the of living value. When they visit this park, future Taitung Area." This plan established the generations will remember the suffering of those "Xiangyang Xinchuan" woodworking touched by the disaster and appreciate the Taiwan workshop in a disused building at spirit of "transcending hardship." Duoliang Elementary School in Taimali Township, Taitung County, conducted training and production tasks, and established operating mechanisms creating jobs for indigenous residents. This plan can serve as a model for post-disaster reconstruction campaigns. Fig3.1 Gathering woody debris from Yanpu Fishing Harbor for shipment. Most of 7. Outlook this wood consists of highly abraded tree trunks with the roots still attached. National forest land is generally located in the upstream portions of watersheds, and the effectiveness of landslide remediation work will have a significant effect on overall watershed management and erosion control work. The Forestry Bureau will continue to implement national forest watershed management and erosion control in order to quickly stabilize forest land, Fig3.2 Woody debris in Xinfeng Village, Gaoshu Township. Most of the wood nurture forest resources, prevent future disasters, consists of trunks with attached roots, and and ensure green forests and clean water for future there are no saw marks. generations.

Although woody debris is a misplaced resource, it has cultural, artistic, and ecological value, is also an important cradle of biodiversity, and can play major roles in life, culture, and art. Through the diversified use of woody debris, community Fig3.3 Heaps of woody debris in development, and village reconstruction, the Shuguang Park, Taimali, Taitung County. The roots are clearly visible. Forestry Bureau has helped residents of disaster-stricken areas escape the shadow of Typhoon Morakot by reviving and building on traditional spirit and culture. In addition, the establishment of the Dongshi International Driftwood Carving Park shows how we should cherish our resources in the wake of disaster. Although woody debris has left the forests where

- 11 - Fig3.4 Recorded valuable woody debris consisting of trunks with the roots still attached and constituting national property. The roots have been abraded into irregular forms. (photo taken in Taitung City)

Fig3.8 Exhibit of creative items made by workworking trainees at the "Xiangyang Xinchuan" woodworking workshop

Fig3.5 Sun, Moon, and Stars—A work at the 2009 East Coast International Driftwood Art Festival

Fig3.6 Ball of the Earth—A work at the 2009 East Coast International Driftwood Art Festival

Fig3.7 Woodcarving -The New Beginnings

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