reviewed paper Explore the Effect of Urban Flood with the Integration of Spatial Analysis Technique Hsueh-Sheng Chang, Chin-Hsien Liao

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1 revewed paper Explore the Effect of Urban Flood wth the Integraton of Spatal Analyss Technque Hsueh-Sheng Chang, Chn-Hsen Lao (Hsueh-Sheng Chang, Assstant Professor, Department of Urban Plannng, Natonal Cheng Kung Unversty, Tanan, Tawan, (Chn-Hsen Lao, Ph.D student, Department of Urban Plannng, Natonal Cheng Kung Unversty, Tanan, Tawan, 1 ABSTRACT Ths study dscusses the urban flood preventon spatal plannng by utlzng the spatal analyss technque to nvestgate urban envronmental feature and dfferent urban flood ssues happened n dfferent locaton whle facng the complcated coexstent relatonshp between urban flood. Typhoon Morakot n Tanan wll be the case study. Ths study utlzes the Geographcally Weghted Regresson (GWR) to explore the varables of urban envronment. The outcome may serve as bass for establshng future land-use ndcators and as decson-makng reference for concerned government agences. Key Words: Urban Flood, Geographcally Weghted Regresson, Land use plan 2 INTRODUCTION In 2005, the World Bank ssued Natural Dsaster Hotspots A Global Rsk Analyss whch ndcted that Tawan may be the most vulnerable to natural hazards place on earth, wth 73 percent of populaton exposed to three or more hazards. Urban flood s a major compound dsaster world-wde that causes serous loss to economc actvtes and mpacts on urban actvtes severely. Ths study focuses on establshng flood ndex to explore the varables of urban envronment that was consdered as one of the most mportant aspects n regonal flood-rsk management. Flood s among the most severe rsks on human lves and propertes, and has become more frequent and severe along wth local economcal development. As the Tawan s cty has been compact rapdly and more stress s put on the land to support the ncreased populaton. In turn, floods that once occurred nfrequently durng pre-development perods have now become more frequent and more severe due to the transformaton of the watershed from rural to urban land uses and urbanzaton phenomenon s one of the man research topcs n the last decade. A comprehensve plan addressng flood hazard management s therefore, necessary. Ths plan should combne land use strateges for each zone wth the careful consderaton of certan structural controls. Ths can be acheved by the mnmal dsrupton of natural envronments. These strateges could serve as basc components n a comprehensve flood management plan n Tawan. Therefore, the mportant ssue s ntegratng spatal analyss technque to nvestgate urban envronmental feature and dfferent compound dsaster ssues happened n dfferent locaton wth complcated coexstent relatonshp between urban and dsaster. The GWR Model was a popular method that appled to modfy the flood problem (Brunsdon et al., 1996; Fotherngham et al., 1998; Platt, 2004; Zhang et al., 2004; 2005; Kupfer and Farrs, 2007). Although ths approach can ncorporate more factors as the predctors and mprove the statstcal sgnfcance of the fttng model, t also ncreases the dffculty of date collectng for predctors to predct the damage n the future. Snce flood damage s affected by many factors, some multple regresson models to ncorporate such factors were also proposed. Ths paper begns by revewng pertnent lterature regardng spatal pattern n assessng urban flood. Next, a GIS flood grade system ntegrates nto the research to enhance the effectveness and precson of measurements. Thus, the am of ths study s to establsh the flood for flood shape area by usng the smallest possble number of ndependent varables, whle consderng the spatal varaton and solvng the problem of spatal autocorrelaton n resduals. 3 METHOD The followng equaton expresses the relatonshp of the flood spatal autocorrelaton, geographcally weghted regresson, and data from study area: 299

2 Explore the Effect of Urban Flood wth the Integraton of Spatal Analyss Technque 3.1 Spatal Autocorrelaton Smlar objects n proxmty to one another are postvely spatally auto correlated, and vce versa, zero autocorrelaton occurs when attrbutes are dstrbuted ndependently n space. Moran s I, as expressed n equaton 4, 5. Id ( ) Where S0 wl l l wl zzl S m m2 z / I, (1) z x x (2) A weght matrx has elements representng the connectons n a set of spatal unt. The may assume any value, but n ths paper we shall confne ourselves to a bnary weght matrx consstng of ones (connected) and zeros (not connected). The dagonal elements of are zero. The varable s mapped onto the spatal unts. The spatal autocorrelaton analyss coeffcent, Moran s I, s s the value of equty for each zone. =1,2,..., I. 3.2 Geographcally Weghted Regresson If the resdual has spatal autocorrelaton, then GWR can be utlsed to modfy the OLS regresson to solve the problem (Brunsdon et al., 1996; Fotherngham et al., 1998; Platt, 2004; Zhang et al., 2004; 2005; Kupfer and Farrs, 2007; Chang, 2008). If the spatally vared characterstcs n flood are taken nto account, equaton 6 can be modfed as: n y b (u,v ) b ( u v ) X (3) 0 k k k 1 where: y s the flood of pont x ; s the flood shape area of pont uv ; s the coordnates of the b uv pont n space; 0 ( b uv ), k ( ) s the realzaton of the contnuous functon at pont ; 1 s the resdual uv of pont ( ). 3.3 Data and study area Located n the southeastern corner of Eurasa Tawan sts n the mddle of the Western Pacfc festoon of slands. It faces the East Chna Sea to the north (600 km from the Ryukyu archpelago), the Bash Channel to the south (350 km from the Phlppnes), the Tawan Strat to the west (averagng 200 km from the Chnese manland), and the Pacfc Ocean to the east. Stuated at the western rm of the Pacfc Basn, the sland plays an mportant role as an East Asan crossroad.these study area Tanan s the forth-grade cty n Tawan, but t's the oldest cty whch has abundant cultural hertage, as the cultural style presented. The methodology wll now be descrbed n greater detal, takng as an example ts plot applcaton for Tanan n Tawan, whch s a town n whch there s present rsk from flood hazard. The extent of the floodng suffered by the nhabtants of Tanan n 2009 s llustrated n Fg REAL CORP 2012: RE-MIXING THE CITY Towards Sustanablty and Reslence?

3 Hsueh-Sheng Chang, Chn-Hsen Lao Fg. 2. Tanan, Tawan, n the floods of Auguster 2009(source: 4 RESULTS 4.1 Explore spatal data analyss of flood area Ths paper through a cases studes n where natural hazard happened areas and the analyss used the data from Tanan n The method ntegrates GIS technques, spatal autocorrelaton analyss (SAA) and local ndcators of spatal assocaton (LISA) to analyze the process of dsaster scale and decson makng s guded by examnaton whch may vary from large regons. The dsasters mappng of locatons wth sgnfcant LISA statstcs, together wth an ndcaton of the type of local spatal assocaton as gven by the quadrants n the Moran scatter plot, provde the bass for a substantve nterpretaton of spatal clusters or spatal outlers. Show n fgure 3. Flood Area A B C D E Explore spatal data analyss Fg.3 The SAA and LISA analyss The result of the SAA analyss on Tanan the value of Moran s I s postve 0.52, and refers to the random and ndependent dstrbuton n regon. LISA provdes nformaton on the relatve mportant of four types of spatal assocaton: (1) hgh hgh, hgh values (above the mean) assocated wth hgh rsk values such as A, B D areas; (2) low low, low values (below the mean) assocated wth low rsk values; (3) low hgh, low values assocated wth hgh rsk values; and (4) hgh low, hgh values assocated wth low rsk values. In the future, the land use plannng suggests strengthenng preventon such as Yong Kang dstrct, Snyng dstrct and Madou dstrct. 4.2 GWR model The GWR model results were more closely examned n ths study to develop fur ther knowledge for later use n modfyng the tradtonal OLS regresson model. The regresson result s shown n Table

4 Explore the Effect of Urban Flood wth the Integraton of Spatal Analyss Technque Effectve Number of Parameters Correlaton Coeffcent (r) Coeffcent of Determnaton (r²) Adjusted (r² Adj) r-square P-valu (*p<0.05) TABLE 2 Global regresson parameter estmates (ns37) The coeffcent of determnaton s whle the resduals plot s shown as n Fg. 2. The applcaton of GWR model mproved the ncreased from 0.36, demonstratng that GWR provdes a better nterpretng ablty than OLS. As shown n Fg. 4, the hstogram of ntercept estmates dsplays three obvous groups. Fgure 6 depcts the spatal dstrbuton of these three groups. There s a sgnfcant clustered pattern ndcatng that basc flood shape area ncrease gradually from west to southwest corner n the study regon shown n fg.5. These parameter estmates ndcate the change of the flood wth the flood shape area, and are ncreased gradually from west to northwest n the study area. 4.3 Land use and flood analyss The analyses of land usng and flood heren cover comparsons of area sze and land usng category n Tanan Cty. In addton to nterpretng the results of prevous analyses of land usng and flood n broad vews, we predct that land usng under lmted control resources has some mpacts to the flood. Flood Hgh Medum Low Land Usng Category Total area(ha) Number Mean S. dev. Agrculture 1, Buldng Area 1,40.2 1, Green Space and Park Agrculture 5, , Buldng Area 1,017 9, Green Space and Park 4, Agrculture , Buldng Area , Green Space and Park TABLE 3 The descrptve statstc of flood In Tanan Cty, 1,254.6 hectares of agrculture area were damaged because of hgh flood. Green space and park were not enough to absorptve capacty n the hgh flood area over 9.9 hectares. The hghest capacty whch green space and park can be absorptve n the Medum flood area s about 5,572.6 hectares. In the past, land use and flood analyses have been used to represent the sze qualtes of land use category. The land use and flood are affected by populaton, land usng constructon, and local dfferences. The constructon of land usng s often related to the geographc envronment and urban development that manly nfluences urban flood ntensty. 5 CONCLUSTION The paper proposed an approach that not only uses the smallest numbers of explaned varables to establsh the flood functons for flood shape area, but also solves the problem n tradtonal regresson models by overlookng the spatal varatons wth floodng loss characterstcs. The ntroducton of the GWR model mproved the coeffcent of determnaton from 0.36 n the orgnal OLS to The GWR model corrects the spatal autocorrelaton problems n resduals wth some drawbacks stll. It produces a dfferent set of estmates for the regresson parameters at each sample ponts. On the other hand, the results of flood and land use analyses ndcate the three level rsk of flood wthn land usng stuaton, taken the urban flood characterstcs of spatal pattern nto consderaton to mprove green space and urban park area, and land usng capacty that supplements urban envronment safety and sustanable development. 302 REAL CORP 2012: RE-MIXING THE CITY Towards Sustanablty and Reslence?

5 6 REFERENCES Hsueh-Sheng Chang, Chn-Hsen Lao Brunsdon, C., A. S. Fotherngham, and M. E. Charlton. 1996: "Geographcally weghted regresson: A method for explorng spatal nonstatonarty." Geographcal Analyss 28: Chang, L. F., C. H. Ln, and M. D. Su. 2008: "Applcaton of geographc weghted regresson to establsh flood-damage functons reflectng spatal varaton." Water Sa 34: Feng, L. H. and G. Y. Luo. 2010: "Proposal for a quanttatve ndex of flood dsasters." Dsasters 34: Fotherngham, A. S., M. E. Charlton, and C. Brunsdon. 1998: "Geographcally weghted regresson: a natural evoluton of the expanson method for spatal data analyss." Envronment and Plannng A 30: Kupfer, J. A. and C. A. Farrs. 2007: "Incorporatng spatal non-statonarty of regresson coeffcents nto predctve vegetaton models." Landscape Ecology 22: Platt, R. V. 2004: "Global and local analyss of fragmentaton n a mountan regon of Colorado." Agrculture Ecosystems & Envronment 101: Zhang, L. J., H. Q. B P. F. Cheng, and C. J. Davs. 2004: "Modelng spatal varaton n tree dameter-heght relatonshps." Forest Ecology and Management 189: Zhang, L. J., J. H. Gove, and L. S. Heath. 2005: "Spatal resdual analyss of sx modelng technques." Ecologcal Modellng 186: