the radar-graphic method for evaluation of the effectiveness of stream ecological engineering

8/11/2019 The Radar-Graphic Method for Evaluation of the Effectiveness of Stream Ecological Engineering

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The SIJ Transactions on Advances in Space Research & Earth Exploration (ASREE), Vol. 1, No. 2, November-December 2013

ISSN: 2347 – 6087 © 2013 | Published by The Standard International Journals (The SIJ) 43

Abstract — Over the past decade in Taiwan, ecological engineering methods acted principally in riverremediation and slope protection. In order to examine the effectiveness of stream restoration, the Index ofStream Restoration Guidance (ISRG) and Radar-Graphic Method (RGM) were used to describe the overallstream condition. Six criteria must be considered in the evaluation of a stream’s ecological environment: waterquality, habitat quality, eco-hydrology, flood prevention, aesthetic and recreational demand, and bank stability.Using the assessment results in the Jilong River overall improvement project, a river located in northernTaiwan, five conclusions were drawn: (1) ISRG scores on stream’s ecological environment and biological

performance are higher at the upstream than at the middle and downstream; (2) good ecological performanceswere observed under the condition of a gentle revetment and wider green belt; (3) type of revetment which are

porous and permeable will create better biodiversity; (4) the ecological performance at the middle anddownstream depends on the human disturbance; (5) the proposed methodology establishes a quantitativeassessment tool and provides a guide to planning and implementing stream restoration projects.

Keywords — Biodiversity; Index of Stream Condition; Jilong River; Radar-Graphic Method; Stream EcologicalEngineering; Stream Restoration.

Abbreviations — Ephemeroptera, Plecoptera, Trichopetera (EPT); Indexes of Biological Integrity (IBI); Indexof Stream Condition (ISC); Index of Stream Restoration Guidance (ISRG); Family-level Biotic Index (FBI);Radar-Graphic Method (RGM); Rapid Bioassessment Protocol III (RBP III).

I. INTRODUCTION

UE to the increase of ecological awareness, Taiwanstarted to seek advanced technology from othercountries in order to modify traditional civil

engineering practices which prioritized development andhuman demands. In the late 1990s, a field research associatedwith environment beautification was launched. The new

philosophy of ecological engineering began to attractacademic institutes’ attention gradually. Government alsoinitiated all sorts of funding for the purposes of a) the

possible limitation of applying it in Taiwan, and b)establishing localized applicable methods in riverreconstruction. Slightly after the water resources relatedagencies’ action, this new trend started to affect soilconservation practices by introducing river bank stabilizationmethods. Followed by valuing the advantage over waterquality control, ecological engineering also contributes to

Taiwan’s environmental engineering since 2003. Thisabstract is a brief introduction to the subject of ecologicalengineering method, which is a whole new concept in thefield of civil engineering. The advantages of using theecological engineering method are not only to satisfy thedemand of safety (i.e. natural hazards control) but also that of

protecting ecosystem and landscape aesthetic.In Taiwan, typhoons are very common during the

summer and bring huge amount of precipitation with them.The development and management works of the rivers inTaiwan were, in the early days, primarily focused on watercontrol for hydraulic facilities, but also considered overalleco-environment. The requirement of landscape creation andeco-environment protection from people are on the rise withthe recent ecological protection concepts. For this reason,Taiwan Water Resource Agency executed the “Jilong RiverOverall Master Plan (Earlier Plan)” from 2002 to 2005[National Taipei University of Technology, 2012] to reduce

D

*Assistant Professor, Department of Civil Engineering, National Taipei University of Technology, Taipei, TAIWAN, ROC.E-Mail: [email protected]

**Professor, Department of Civil Engineering, National Taipei University of Technology, Taipei, TAIWAN, ROC. E-Mail: [email protected]***Chief Secretary, Water Resources Department, New Taipei City Government, New Taipei City, TAIWAN, ROC.

E-Mail: [email protected]****Master, Department of Civil Engineering, National Taipei University of Technology, Taipei, TAIWAN, ROC.

E-Mail: [email protected]

Chia-Chun HO*, Jen-Yang LIN**, Tsung-Ming YANG*** & Kuan-Han CHOU****

The Radar-Graphic Method forEvaluation of the Effectiveness of

Stream Ecological Engineering





the risk of flooding and improve the environment. Figure 1 below shows the failure of the Jilong River revetment whichsuffered a serious flooding in 2001. Because of this,ecological engineering methods were adopted to rebuild therevetment. Figure 2 shows the current status of this revetmentusing gabion method and vegetation blanket. In order tounderstand the effectiveness of revetment while usingecological engineering method, the ecological investigation

and basis of construction work of the Jilong River was

divided between the upstream, midstream and downstream.The project was completed over several years, mainly due tothe fact that the river ecological data had to satisfy the designand guidelines of an eco-environment adapted for the river.Thus, the investigation of the before and after conditionswere necessary. After reviewing the effect of the environmentdue to the changes brought by the master plan, reinforcementstrategies and suggestions should be proposed as to reach

higher ecological environment influence.

(a) Upstream (b) Midstream

Figure 1: A Failure Cases of Revetment

(a) Upstream (b) MidstreamFigure 2: The Current Status after Construction

II. T HE ASSESSMENT OF THE S TREAM

C ONDITION

The effectiveness of the stream remediation mostly focusedon the hydraulic structure safety. It is rarely from anecological point of view that we examine the effectiveness.However, the performance of the biological environmentshould be included in the assessment of stream remediation

projects. Researchers have published several studies on the biotic index.

2.1. Biological I ndex

Previous studies proposed a different index for bio-environment. Karr (1991) adopted fish to be a bio-indicatorand proposed the Indexes of Biological Integrity (IBI).Depending on the IBI score, the biological condition can beclassified within four categories, as shown in Table 1.Table 1: The Biological Condition Category and Score Range of IBI

Biological Condition Category Score RangeNon-impaired 30-39Slightly impaired 21-29Moderately impaired 11-20Severely impaired 0-10

Base on the water quality and water pollution resistanceof fish, a Family-level Biotic Index (FBI) was proposed byHilsenhoff (1998). Table 2 shows the FBI score range.

Table 2: Water Quality and Score Range of FBIWater Quality Score Range Water Quality Score RangeExcellent 0.00-3.75 Fairly Poor 5.76-6.50Very Good 3.76-4.25 Poor 6.51-7.25Good 4.26-5.00 Very Poor 7.26-10.00Fair 5.01-5.75

Plafkin et al., (1989) adopted seven bio-indexes toevaluate water quality and stream environment, and therefore

the Rapid Bio-assessment Protocol III (RBP III) was advised.The indexes include taxa richness, Hilsenhoff biotic index,ratio of scrapers/fil. collectors, ratio of EPT (Ephemeroptera,Plecoptera, Trichopetera) and chironomid abundances,contribution of dominant taxon (%), EPT index, andcommunity loss index. Table 3 shows the biologicalcondition scoring criteria.





Table 3: Biological Condition Scoring Criteria of RBP III

Water QualityBiological Condition Scoring Criteria

6 4 2 0Taxa richness >80% 60%-80% 40%-60% <40%Hilsenhoff biotic index >85% 70%-85% 50%-70% <50%Ratio of scrapers/fil. collectors >50% 35%-50% 20%-35% <20%ratio of EPT and chironomid

abundances>75% 50%-75% 25%-50% <25%

Contribution of dominant taxon (%) <20% 20%-30% 30%-40% >40%EPT index >90% 80%-90% 70%-80% <70%Community loss index <0.3 0.3-0.5 0.5-0.7 >0.7

2.2. I ndex of Stream Condition

The Index of Stream Condition (ISC) is the first complete andcomprehensive study of the environmental condition of riversanywhere in Australia and was also the first integratedmeasure of river condition in Australia [Ladson & White,1999].

Australian Governments are increasing their focus on

rivers via legislative, research and rehabilitation actions.Within this environment, the Index of Stream Condition(ISC) was developed in response to a managerial need to 'useindicators to track aspects of environmental condition and

provide managerially or scientifically useful information'[Ladson et al., 1999].

The ISC consists of five sub-indices, which represent keycomponents of stream condition (Table 4). Each sub-indexconsists of indicators, which are calculated using datacollected in the field or by desk based methods. Eachindicator is then assigned a rating score (Table 5). Sub-indexscores are calculated by summing the component indicatorscores, and the overall ISC score is calculated by summingthe sub-index scores [Ladson et al., 1999].

Table 4: List of Indicators used in the Index of Stream Condition [Ladson et al., 1999]Sub-Index Basis for Sub-Index Value Indicators within Sub-Index

Hydrology Comparison of the current flowregime with the flow regimeexisting under natural conditions.

Amended annual proportional flow deviation Daily flow variation due to change of catchment permeability Daily flow variation due to peaking hydroelectricity stations

Physical

Form

Assessment of channel stability

and amount of physical habitat.

Bank stability

Bed stability Impact of artificial barriers on fish migration Instream physical habitat

StreamsideZone

Assessment of quality and quantityof streamside vegetation.

Width of streamside zone Longitudinal continuity Structural intactness Cover of exotic vegetation Regeneration of indigenous woody vegetation Billabong condition

WaterQuality

Assessment of key water quality parameters.

Total phosphorus Turbidity Electrical conductivity

Alkalinity / acidityAquatic Presence of macro invertebrate

families SIGNAL AusRivAS

The ISC uses a rating system to assess stream condition.The use of a rating system is designed to provide as muchresolution as possible, within the constraint that there is'limited knowledge of the relationship between a change inthe indicator and environmental effects' [Ladson & White,1999]. Values for each indicator are assigned a rating on the

basis of comparison with a reference state (Figure 3). These

ratings are summed to produce an overall score that reflects acontinuum of stream conditions from excellent to very poor.In calculating the overall ISC scores, the scores for each sub-index and for each indicator can be weighted, depending onthe perceived importance of each, or the availability of data[Ladson & White, 1999].





Figure 3: Assessment of Stream Condition using the ISC [Ladson etal., 1999]

2.3. I ndex of Stream Restoration Gui dance (I SRG)

Base on the Index of Stream Condition (ISC) andincorporation factors unique to Taiwan, Lin et al., (2005)

proposed the Index of Stream Restoration Guidance (ISRG)and developed six indices for evaluating stream restoration

projects using the ecological engineering methods. Theseindices include considerations for stream ecologicalenvironment, water quality and habitat, eco-hydrology, flood

prevention, aesthetics and recreation demands, and bankstability requirements. The indicators and score within thosesix indices are shown in Table 5. According to the score ofthose six indices, the Radar-Graphic Method (RGM) wasused to evaluate the effectiveness of stream ecologicalengineering. Figure 4 shows the best performance of RGM onstream restoration. Three of the indices scores (flood

prevention, aesthetics and recreation demands, and bankstability requirements) are very low. It indicates not only thatthe hydraulic design for this stream is satisfactory but alsothat the effectiveness of ecological environment is superior.

Table 5: Indicators used in the Index of Stream Restoration Guidance [Lin et al., 2005]

Sub-Index Indicators within Sub-Index Score(X) Conversion Coeff. Sub-Index Score

A. Stream ecological environment

Width of streamside zone 0-4( X) (10/10) 0-10 Longitudinal continuity 0-4

Cover of vegetation 0-2

B. Bank stability requirements

Geology of river bank0-4 ( X) (10/4) 0-10 Erosion of river bank

Erosion of bank toe

C. Water quality and habitat River pollution index 0-16

( X) (10/20) 0-10 Fish species and populations 0-4

D. Flood prevention

Protected targets Flood history Flood damages Investment cost

0-10 ( X) (10/10) 0-10

E. Eco-hydrology

Ecological instream flows 0-10( X) (10/18) 0-10 Aquatic habitat environment 0-4

Bed stability 0-4

F. Aesthetics and recreationdemands

Landscape aesthetics Promenade recreation Environmental education Irrigation

0-10 ( X) (10/10) 0-10

Figure 4: Illustration of the Best Performance of RGM on StreamRestoration

This paper is a case study using ISRG and furthermore

the ecological environment investigation was carried out ingreat detail to confirm the feasibility of RGM.

III. T HE E VALUATION R ESULTS OF J ILONG

R IVER USING RGM

“Jilong River Overall Master Plan (Earlier Plan)” was proposed after permission of the Taiwan Executive Yuan inMay, 2002. The 3 year plan was executed between 2002 to2005 and received a funding of $12 billion US dollars. The

plan has now been completed for 7 years and has undergone a

IndicatorRating

Corresponding reference categoryExample values:

pH range

4 Very close to reference state 6.5-7.5

3 Minor modification from refer ence state 6. 0-<6.5 or 7.5-8. 0

2 Moderat e modi ficat ion from re fe rence st ate 5 .5-<6 .0 o r 8 .0 -8 .5

1 Maj or modification fr om r ef er ence state 4. 5-<5.5 or 8.5-9. 5

0 Extreme modification from refer ence state <4.5 or >9.5

Overall ISC score Stream condition

45-50 Excellent

35-44 Good

25-34 Marginal

15-24 Poor

<14 Very poor

1. Calculate ratings for indicators

2. Calculate ISC score

Rat ings are summed within each sub-index, then sub-index scores are summedto produce an overall ISC score.

Repeated for each indicator.Reference ranges are derivedfrom existing literature.

02468

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B

C

D

E

F

A: Stream ecological environment

B:Bank stability requirements

C:Water quality and habitat

D:Flood prevention

E:Eco-hydrology

F:Aesthetics and recreationdemands





number of typhoons. In order to know the performance of this plan, RGM was used to evaluate of the effectiveness ofstream ecological engineering in this study. Further analysisof significant improvement master methods has been

performed to provide as criterion for further master plan ofother reaches. Assessment of non-significant master methodshas been executed and reinforcement strategies have been

proposed in this study. In order to understand the

effectiveness of stream ecological engineering, three surveystations were investigated which were located upstream,

midstream and downstream. According to the six sub-indexof the ISRG, to calculate their scores and graph the RGMs.

3.1. Upstream of Ji long River

The upstream channel of Jilong River, with a length of11.7km and a mean height of 12.6m, was improved usinggabion, stone-paved and geo-grid reinforced revetment. Riverinvestigation of current status and the change of environment

before and after master plan have been executed to review theinfluence and improvement of the master plan. Theassessment results at the upstream are shown on Table 6.

Table 6: The Assessment Results of ISRG at the Upstream of Jilong River

Sub-index Indicators within sub-indexPoint(X)

Conversion Coeff. Sub-Index Score


Width of streamside zone 37 (10/10) 7.0 Longitudinal continuity 3

Cover of vegetation 1


Geology of river bank1 1 (10/4) 2.5 Erosion of river bank

Erosion of bank toe

C. Water quality and habitat River pollution index 12

16 (10/20) 8.0 Fish species and populations 4

D. Flood prevention


1.8 1.8 (10/10) 1.8

E. Eco-hydrology

Ecological instream flows 1016 (10/18) 8.9 Aquatic habitat environment 3

Bed stability 3

F. Aesthetics and recreation demands


3 3 (10/10) 3.0

Radar-Graphic Method (RGM)

A. Stream Ecological Environment

The sub-index of stream ecological environment includeswidth of streamside zone, longitudinal continuity and coverof vegetation. Figure 5 shows the current situation of streamecological environment. The width of the streamside zone is127.5 meters and it is 2.56 times the breadth of the river ’sactive channel. This area shows a good performance from thevegetation except the zone under the bridge, furthermore thevegetation cover rate at the upstream is 78% done byshrubbery and grass. The comprehensive improvementobserved in result to our field investigation ensued in a sub-index score of 7.0 on stream ecological environment. Figure 5: The Current Situation of Stream Ecological Environment

at the Upstream of Jilong River [Ho et al., 2013]

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B

C

D

E

F





B. Bank Stability Requirements

In order to know the river bank stability and its erosionsituation, the bathymetry survey of each cross-section wereemployed in this study. Choosing one of the cross-sections atthe upstream and comparing its bathymetry results betweenthe 2006 and 2011 survey (see Figure 6), we can notice aslight difference in the improvement works completed after 1year (2006) and 6 years (2011) of Section K-70. We cantherefore say that the bank stability requirement is very lowand scored 1.0 point; hence the sub-index score is 2.5.

Figure 6: The Results of the Bathymetry Survey in 2006 and 2011.(Section K-70)

C. Water Quality and Habitat

There are 5 water quality monitoring stations at the upstreamof Jilong River. Their evalutation of the average value fortotal phosphorus in 2011 is 0.005 mg/L, turbidity is 8.97

NTU, conductivity is 182 mho/ cm-25°C, and pH is 7.8.According to the scoring criteria of ISRG, the score for theriver pollution index is 12 points.

Moreover, the aquatic life in Jilong River wasinvestigated from 2010 to 2012 and recorded 14 species offish at the upstream. All of the fish are native speciesincluding the Varicorhinus barbatulus, Acrossocheilus

paradoxus, Zacco platypus, Formosania lacustre, and so on(Figure 7). Hence, in accordance with the scoring criteria ofISRG, the score of fish species and populations is 4 points.Consequently, the sub-index score of water quality andhabitat is 8.0.

(a) Varicorhinus barbatulus (b) Acrossocheilus paradoxus

(c) Zacco platypus (d) Formosania lacustrFigure 7: The Native Fishes at the Upstream of Jilong River

D. Flood Prevention

The land purpose surrounding the Jilong River’s upstream is predominantly based on agriculture and forestry. The protected targets in potential flooding regions consist of onlysome of the constructions such as roads, bridges, and

buildings. The heavy rainfalls brought by typhoon NARI inSeptember 2001 had not caused significant damages to roadsand properties at this area. In view of the above, the sub-index score of flood prevention is 1.8.

E. Eco-Hydrology

The score for the ecological instream flows is 10 because theflow rate throughout the year has been consistently greaterthan 0.5 cms, even without lateral construction in the riverchannel at the upstream. It is a near ideal aquatic habitat withnumerous pieces of coarse wood debris from indigenousspecies and so scored 3 points. Furthermore, it has goodvegetative cover, some minor isolated erosion, and nocontinuous damage to the bank structure or vegetation itself,

bringing the indicator for the bed stability to 3 points. Finally,when calculating the sub-index for the eco-hydrology, we geta score of 8.9.





F. Aesthetics and Recreation Demands

The upstream of Jilong River has some small-scale farms bythe streamside which makes use of stream water forirrigation. Therefore, the sub-index score of aesthetics andrecreation demands is 3.0.

The chart of Radar-Graphic Method is also show inTable 6. It indicates the steep riverbank caused by the poor

performance of vegetation at the upstream; hence the score ofsub-index A is not high. The good water quality and flow rate

provide an excellent biological environment andconsequently got the high score on sub-index C and E.Moreover, the riverbank is located on the bedrock, andtherefore does not produce the erosion of bank toe. For thisreason, the score on bank stability requirement is low.Briefly, the ecological engineering method achieved

remarkable improvement in the upstream and the shape of theRGM presents a triangle arrow.

3.2. M idstream of Ji long River

The midstream channel of Jilong River has a length of19.9km and a mean height of 10.2m. Besides gabion, stone-

paved and geo-grid reinforced revetment, the revetmentimprovement works used a number of concrete banks to

protect the residents living by the river side as well as spreadvegetation blanket on the surface of concrete banks.Investigation of the river ’s current status and the before andafter environment change of the master plan have beenexecuted to review the influence and improvement of themaster plan. The assessment results at the midstream areshown on Table 7.

Table 7: The Assessment Results of ISRG at the Midstream of Jilong River

Sub-index Indicators within sub-indexPoint

(X)Conversion

Coeff.Sub-Index

Score





Geology of river bank1 1 (10/4) 2.5 Erosion of river bank

Erosion of bank toe



D. Flood prevention


4.0 4 (10/10) 4.0

E. Eco-hydrology

Ecological instream flows 8

12 (10/18)6.7

Aquatic habitatenvironment

2

Bed stability 2



7.5 7.5 (10/10) 7.5



Figure 8 shows the current situation of stream ecologicalenvironment. The width of the streamside zone is 136.7m andit is 3.12 times the breadth of the river ’s active channel.Because of the wide and gentle beach, the vegetation shows a

nice performance in this area. Furthermore, the vegetationcover rate at the midstream is 89% done by shrubbery andgrass. The comprehensive improvement observed in result toour field investigation ensued in a sub-index score of 9.0 onstream ecological environment.

02468

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B

C

D

E

F





Figure 8: The Current Situation of Stream Ecological Environmentat the Midstream of Jilong River [Ho et al., 2013]


Figure 9 shows a comparison of the results of the bathymetrysurvey performed in 2006 and 2011. Some minor isolatederosion cases could be noticed on the river bed from theimprovement works completed after 1 year (2006) and 6years (2011) of the Section K-88. However, the surface of theriver bank and its toe are still stable as well as nodisplacement happened from 2006 to 2011. So the sub-indexof bank stability requirement score is 2.5.



A total of 4 water quality monitoring stations wereestablished at the midstream of Jilong River. Their evaluationof the average value for total phosphorus in 2011 is 0.0143mg/L, turbidity is 18.54 NTU, conductivity is 325 mho/cm-25°C, and pH is 7.5. According to the scoring criteria ofISRG, the score of river pollution index is 11 points.

Moreover, the aquatic life in Jilong River wasinvestigated from 2010 to 2012 and recorded 19 species offish at the midstream. At this particular segment of the river,not only native fishes were found but also exotic ones such asCyprinus carpip, Oreochromis sp., Channa striata,Hypostomus placostomus, and so on (Figure 10). Hence, inaccordance with the scoring criteria of ISRG, the score of fishspecies and populations is 3 points. Consequently, the sub-index score of water quality and habitat is 7.0.

(a) Cyprinus carpip (b) Oreochromis sp

(c) Channa striata (d) Hypostomus placostomusFigure 10: The Exotic Fishes at the Midstream of Jilong River

D. Flood Prevention

The land purpose of Jilong River’s midstream is predominantly based on agriculture and small town. The protected targets in potential flooding regions include roads,

bridges, and buildings. Hence, the sub-index score of flood prevention is 4.0.





E. Eco-hydrology

The score of ecological instream flows is 8 due to the flowrate throughout the year being greater than 0.5 cms, achievedwith some lateral construction in the river channel. It is amoderate variation from an ideal aquatic habitat withmoderate visible pieces of coarse wood debris fromindigenous species, therefore the scored attributed if of 2

points. Furthermore, as the banks were held by discontinuousvegetation and showed a generally stable toe, the indicator of

bed stability received 2 points. Finally, the calculated sub-index score of eco-hydrology is 6.7.

F. Aesthetics and Recreation Demands

The riverside of the midstream has a number of bicycle paths, parks, and river-accessible spaces. Therefore, the sub-indexscore of aesthetics and recreation demands is 7.5.

The chart of Radar-Graphic Method is also show inTable 7. The current situation displays a nice result on

vegetation of gabion revetment wall and provides a good biological habitat environment. Thus the score of sub-indexA, C and F are high; nevertheless, they are lower than thescore observed at the upstream. That can be explained by the

bad results in water quality and a higher human disturbancethan at the upstream. In addition, the aesthetics and recreationdemands are higher than at the upstream.

3.3.

Downstream of Ji long RiverThe downstream channel of Jilong River has a length of15.2km and a mean height of 8.7m. Because it is adjacent to adense residential area, a large number of concrete banks wereadopted in its improvement project. In order to build a goodecological environment, vegetation blankets were spread onthe surface of some concrete banks. . Investigation of theriver’s current status and the before and after environmentchange of the master plan have been executed to review theinfluence and improvement of the master plan. Theassessment results at the downstream are shown on Table 8.

Table 8: The Assessment Results of ISRG at the Downstream of Jilong River

Sub-index Indicators within sub-index Point(X) Conversion Coeff. Sub-Index Score





Geology of river bank1.8 1.8 (10/4) 4.5 Erosion of river bank

Erosion of bank toe



D. Flood prevention

Protected targets Flood history Flood damages

Investment cost

8.0 8 (10/10) 8.0

E. Eco-hydrology

Ecological instream flows 710 (10/18) 5.6 Aquatic habitat environment 2

Bed stability 1



8.5 8.5 (10/10) 8.5



Figure 11 shows the current situation of the downstreamecological environment. The downstream width of the

streamside zone is 102.3m and it is 0.67 times the breadth ofthe river ’s active channel. In this region, the concrete bankshold a discontinuous vegetation and has a cover rate of 63%achieved by shrubbery and grass. The comprehensive

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B

C

D

E

F





improvement observed in result to our field investigationensued in a sub-index score of 5.0 on stream ecologicalenvironment.

Figure 11: The Current Situation of Stream Ecological Environmentat the Downstream of Jilong River [Ho et al., 2013]


Figure 12 shows a comparison of the results of the bathymetry survey performed in 2006 and 2011. An obviouserosion of the river bed of Section K-101 can be noticed fromthe improvement works completed after 1 year (2006) and 6years (2011); moreover, some damage to the bank structureand vegetation can be clearly noticed. The situation of thisregion is moderate bed degradation and therefore the sub-index of bank stability requirement score is 4.5.



A total of 4 water quality monitoring stations were placed inthe downstream of Jilong River and their monitored averagevalue for total phosphorus in 2011 is 0.0265 mg/L, turbidityis 27.9 NTU, conductivity is 383 mho/cm-25°C, and pH is

7.6. According to the scoring criteria of ISRG, the score ofriver pollution index is 10 points.

Moreover, the aquatic life in Jilong River wasinvestigated between 2010 and 2012 and recorded 22 speciesof fish at the downstream. Most of the exotic fishes and the

peripheral division freshwater fishes in midstream were alsoreported to be living in the downstream, such as Mugilcephalus, Nematalosa nasus, Awaous melanocephalus,Acanthopagrus schlegeli, and so on (Figure 13). Hence, inaccordance with the scoring criteria of ISRG, the score of fishspecies and populations is 2 points. Consequently, the sub-index score of water quality and habitat is 6.0.

(a) Mugil cephalus (b) Nematalosa nasus

(c) Awaous melanocephalus (d) Acanthopagrus schlegeliFigure 13: The Peripheral Division Freshwater Fishes at the Downstream of Jilong River

D. Flood Prevention

The land surrounding the Jilong River’s downstream is predominantly urban. It is a densely inhabited district and the protected targets in potential flooding regions include roads,

bridges, and buildings. This region also is an important business area. Heavy rainfalls brought by typhoon NARI inSeptember 2001 caused serious damages to the roads and

properties at this area. Hence, the sub-index score of flood prevention is 8.0.




| bl h d b h d d l l ( h )

Tsung-Ming YANGEducation: Master, of ConstructionEngineering, National Taiwan University ofScience and Technology, TaiwanPosition: Chief Secretary, Water ResourcesDepartment, New Taipei City Government,

New Taipei City, TaiwanResearch interest: Water resourceManagement Waste water Treatment Flow

Measure Number of papers published: 2 Number of conferences/seminars attended: 11

Kuan-Han CHOU Education: Master, Civil Engineering,

National Taipei University of Technology,TaiwanPosition: Engineer, 5th River ManagementOffice, Water Resource Agency, TaiwanResearch interest: Geosynthetics application,Erosion behaviour of revetments

Number of papers published: 1

Number of conferences/seminars attended: 2

the radar-graphic method for evaluation of the effectiveness of stream ecological engineering

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