BEST-MANAGEMENT-PRACTICES SELECTION STRATEGY IN …staff.ui.ac.id/system/files/users/dwita.sutjiningsih/publication/01hathi-manado-full... · Dwinanti Rika Marthanty, Dwita Sutjiningsih,

International Seminar on “Climate Change Impacts on Water Resources and Coastal Management in Developing Countries”.

BEST-MANAGEMENT-PRACTICES

SELECTION STRATEGY

IN RAIN WATER MANAGEMENT

BASED ON

AREA PROPERTY UNIT CHARACTERISTIC

Manado 11-13 May, 2009

Dwinanti Rika Marthanty, Dwita Sutjiningsih, Herr Soeryantono

International Seminar on “Climate Change Impacts on Water Resources and Coastal Management in Developing Countries”. Manado 11-13 May, 2009. 2

FULL PAPER

BEST-MANAGEMENT-PRACTICES SELECTION STRATEGY IN

RAIN WATER MANAGEMENT BASED ON AREA PROPERTY UNIT CHARACTERISTIC

Dwinanti Rika Marthanty

Civil Engineering Department, University of Indonesia, Kampus UI Depok Depok, 16424, Indonesia, [email protected]

Dr-Ing. Dwita Sutjiningsih


Herr Soeryantono, PhD


ABSTRACT: There are researches regarding to climate change that concluded increasing in annual precipitation across the majority of the Indonesian islands. Recently, in rapid developing areas such as Depok and Bogor, West Java, Indonesia, where Sugutamu Creek, Sub-Watershed of Ciliwung River is located, the trend of volume and rate of runoff tend to be increased due to land-use changes. This phenomenon is proved by widened flooded area. By employing micro-scale and distributing best management practices (BMPs), rain water management is used to achieve a low impact development conditions. This research aims to develop selection strategy of BMP based on local community social and economy condition which is represented by area property unit. In this research, the community of Sugutamu was grouped into three categories: the first category has area property less than or equal to 90 sqm; the second category has property area between 90 to 150 sqm; and the third category has property area more than 150 sqm. Since BMP design was generated based on different characteristics from the study area, the design has been adapted to meet the current conditions. Therefore, selected BMPs are designed for each community category. The research result could be benefit to the community and contribute to local government policy in water resources management. It is also recommended to continue the research by piloting BMP implementation at Sugutamu.

KEYWORDS: Ciliwung, Sugutamu, land-use, best-management-practices, rain water management, low impact development, selection strategy, area property unit characteristic.

1. INTRODUCTION

Urbanization has a temporal dimension in that rural watersheds are transferred to urban watersheds with increasing land development (Matteo et sl. 2006). Built infrastructure is becoming an increasing and integral part of waters throughout the world. A higher proportion of built components in watersheds have a significant effect on hydrologic and ecosystem functions (Booth et al. 2002; Randhir 2003; Matteo et al. 2006). The effects of stormwater runoff on stream ecosystems are exacerbated by urbanization and coincident increase in



impervious surface in a watershed. Proliferation of impervious surface allows more water from rain events to reach a stream faster, causing higher peak flows that can lead to stream alteration and habitat degradation (Thurston 2006). Recently, in rapid developing areas such as Depok and Bogor, West Java, Indonesia, where Sugutamu Creek, Sub-Watershed of Ciliwung River is located, the trend of volume and rate of runoff tend to be increased due to land-use changes. Urbanization Sugutamu watershed face in vulnerability condition that is caused by decreasing groundwater level. This condition is worsened by groundwater drawing for domestic use.

The studies before found that stream channel instability is a result of the urbanization of watershed hydrology. The aquatic ecosystems most directly affected by urbanization are the small streams and wetlands. Alterations of urban streams and fill in wetlands result in watershed health degradation. The most importance impacts of degradation that are changes in hydrology, riparian corridor, physical habitat within the streams, and water quality (B.C. MWLAP 2002). Due to population growth and land acquisition, dwelling are built up along Sugutamu riparian coridor and flood plain which affect stream channel instability and watershed health.

By employing micro-scale and distributing best management practices (BMPs), rain water management is used to achieve a low impact development conditions. There are selected BMPs that proposed for Sugutamu sub-watershed. The need for an ecosystem-based approach to urban watershed also emphasizes the integral role of humans (Van-Wasseneaer et al. 2000; Matteo et el. 2006). This research aims to develop selection strategy of BMP based on local community social and economy condition which is represented by area property unit.

2. METHODOLOGY

A conceptual representation framework is presented as in Figure 1. It presents the rainfall-runoff process on a watershed as a hydrologic system. Rainfall excess or direct runoff is the water that eventually becomes flood runoff. Three process prevent some of the rainfall from becoming immediate runoff and are therefore considered as losses. Those process are interception, depression storage, and infiltration. For practical estimation of rainfall excess, the SCS method is widely used for estimating floods on small to medium-sized ungauged drainage basins. Choice and validity of rainfall loss method depend on the type of problem, the data available, and the runoff processes which are likely to be dominant (Maidment 1993).

The purpose of an Rain Water Management or Integrated Stormwater Management Plan (ISMP) is to provide a clear picture of how to be proactive in applying land use planning tools to protect property and aquatic habitat, while at the same time accommodating land development and population growth. Guiding principles of ISMP is ADAPT which are: Agree that stormwater is a resource; Design for the complete spectrum of rainfall events; Act on a priority basis in at-risk drainage catchments; Plan at four scales – regional, watershed, neighborhood & site; and Test solutions and reduce costs by adaptive management. Design for the complete spectrum of rainfall events, means that integrated stormwater solutions require site design practices that provide: rainfall capture for small storms, runoff control for large storms, and flood risk management for the extreme storms. With integrated strategy, the design forms the foundation of integrated stormwater solutions that mimic the most effective stormwater management system of all – a naturally vegetated watershed (B.C. MWLAP



2002). Rain water management occupies variation BMP on microscale area that of distributed throughout watershed to achived pre-development hydrologic condition.

Low Impact Development (LID) methods goal is to mimic the pre-development site hydrology using site design techniques that store, infiltrate, evaporate, and detain runoff. Use of these techniques helps to reduce off-site runoff and ensure adequate groundwater recharge (P.G.C. DER 1999). LID design techniques employs integrated best management practices (BMPs) to provide additional hydrologic control of peak discharge and runoff volume.

Figure 1. Conceptual Framework

The emphasis here is on simple-to-use techniques. Using operator omega Ω, rainfall loss is represented by curve number or CN to estimate flood runoff. CN depends on soil type, land cover and hydrologic condition (SCS 1985). In the system boundary of watershed, rainfall is the input, distributed homogeneous in space. The streamflow is the output, concentrated surface runoff at watershed outlet (Maidment 1993). Estimating surface runoff from rainfall is represented by curve-number or CN of SCS methods. Herewith, CN is can be altered and reduced by employing BMPs on site-plan. BMPs implementation is to put into practice all design techniques for the complete spectrum of rainfall events.

Most urban areas are only partially covered by impervious surfaces: the soil remains an important factor in runoff estimates. Urbanization has a greater effect on runoff in watersheds with soils having high infiltration rates (sands and gravels) than in watersheds predominantly of silts and clays, which generally have low infiltration rates. As a result of urbanization, the soil profile may be considerably altered and the listed Hydrologic Soil Group (USDA 1955) classification may no longer apply. In this circumstance, the study to determine HSG according to the land characteristic at Sugutamu is listed in table 1 (CED UI 2007). CN number is drawn form infiltrometer and rainfall measurement based SCS method. Noted that these CN number are specific for land use pointed location, and not described Sugutamu CN area. Determination of Sugutamu CN area is described at sub-section 2.2.

Rainfall P

Surface Runoff Q

Losses

Interception I Infiltration f Depression Sto.

Watershed A

Impervious Pervious

Input I(t)

Output O(t) Q [mm]

CN

P [mm]

Operator Ω



Table 1. Sugutamu Hydrologic Soil Group Profiles

No. Land Type fc CN HSG CN Location cm/h Field SCS

1 Residential, downstream Sugutamu 0.0019 91.16 D 91

Jl. Jelutung

2 Row Crops, downstream Sugutamu 3.3310 66.82 A 68

Depok II Tengah (Jl. Proklamasi)

3 Open Space, downstream Sugutamu 7.2104 36.15 A 36

Depok II Tengah (Jl. Proklamasi)

4 Residential, downstream Sugutamu 2.6834 16.66 A 77

Depok II Tengah (Jl. Seruling Raya)

5 Open Space, downstream Sugutamu 4.3642 55.91 A 49

Depok II Tengah (Jl. Seruling 6)

6 Residential, midstream Sugutamu 2.4486 65.11 A 68

Mutiara Depok

7 Row Crops, upstream Sugutamu 1.0586 84.06 A 68

Pabuaran

8 Fallow, upstream Sugutamu 0.1000 25.56 D 73

Pabuaran

9 Residential, upstream Sugutamu 0.4161 84.12 B 74

Pabuaran

10 Residential, upstream Sugutamu 1.4489 84.57 A 74

Cikaret

Any disturbance of a soil profile can significantly change its infiltration characteristics. With urbanization, native soil profiles may be mixed or removed or fill material from other areas may be introduced. Therefore, a method based on surface soil texture is given in by Brakensiek and Rawls (1983) for determining the HSG classification for disturbed soils (SCS 1986).

2.1 MEASUREMENTS

2.1.1 Selection of Measurement Location

Sugutamu creek is located at two cities, Depok and Bogor, West Java. In figure 2, left side is shown land-use, soil type, and hydrogeology characteristics. Sugutamu is grouped into alluvium and low to midlevel groundwater potential. Land-use characteristic is dominated by residential and row crops. Since Sugutamu development and population is growing higher there is land use changing from sub-urban and rural to urban area.

2.1.2 Rainfall Measurement (Nonrecording Gaging)

Curve numbers describe average conditions that are useful for design purposes. If the rainfall event used is a historical storm, the modeling accuracy decreases. Use the runoff curve number equation with caution when re-creating specific features of an actual storm. The equation does not contain an expression for time and, therefore, does not account for rainfall



duration or intensity (Maidment 1993). Herewith figure 3 is shown actual rainfall that was measured at Sugutamu watershed.

2.1.3 Measuring Streamflow (Velocity-Area Gaging Methods)

Streamflow measurement was conducted to develop rating curve of Sugutamu creek. Measurement location was selected where there are converging flow, absence of backwater, smooth cross section, and accessibility. Sugutamu rating curve is shown at figure 4. Ration of impervious to pervious area of Sugutamu is around 80 to 20.

Figure 2. Study Area Sugutamu Upstream Watershed

Figure 3. Daily Rainfall Measurement at Sugutamu



Figure 4. Sugutamu Rating Curve

2.2 SUGUTAMU CURVE NUMBER AREA (SCS METHODS)

The process of measuring streamflow or discharge for short-term studies is called stream gaging. This research used direct measurement that was velocity-area gaging with tool current-meter. Discharge can be measured directly by observing water surface elevation. The stage-discharge relation is called a rating-curve or rating table. Its form is determined by configuration of the stream channel in the measurement reach. Rainfall measurement was using nonrecording rain gage on site directly as long as streamflow measurement was taken. CN number is calculated by drawing from basics SCS equation. Noted that, the empirical relation Ia=0.2S was used as best approximation from observed data.

SPSPQ

8,0)2,0(

2

22

+−

=………………………………………(1)

101000

−=CN

S………………………………………(2)

From observation, Sugutamu CN area average number is 98.52, as in table 2. It is not represent Sugutamu CN pointed location, and can be concluded as Sugutamu area characteristic is “impervious” or “urbanized”, though Sugutamu is located at the upper-side Greater Jakarta.

Table 2. Sugutamu CN Area

1 2 3 4 5 6 7 8 9 10 11

P P P Tc Tc Q (P-0.2S)^2 (P+0.8S) [6]-

([7]/([8]*[5]) S CN

[mm] [m] [in] [hour] [second] [in] [in2] [in] [in]

24 0.024 6.096 164.7 592831 7.77613E-06 36.94 6.17 0.00 0.0905 99.10

196 0.196 49.78 59.7 214919 8.78002E-06 2464.76 50.33 0.00 0.6885 93.56

12 0.012 3.048 262.1 943450 1.0868E-05 0.00 0.03 0.00 0.0357 99.64



1 2 3 4 5 6 7 8 9 10 11

P P P Tc Tc Q (P-0.2S)^2 (P+0.8S) [6]-

([7]/([8]*[5]) S CN

[mm] [m] [in] [hour] [second] [in] [in2] [in] [in]

22.5 0.023 5.715 209.3 753314 1.28684E-05 0.00 0.04 0.00 0.0560 99.44

1.5 0.002 0.381 831.6 3E+06 1.34113E-05 0.00 0.00 0.00 0.0035 99.96

33.5 0.034 8.509 156.3 562690 1.06816E-05 0.00 0.08 0.00 0.1004 99.01

36 0.036 9.144 150.4 541273 1.0718E-05 0.00 0.09 0.00 0.1085 98.93

Sugutamu CN Area Average 98.52

Simple techniques of BMP implementation is needed to improve hydrologic condition of Sugutamu. Hydrology analysis is taken into account to reduce Sugutamu CN area.

2.3 SUGUTAMU COMMUNITY CHARACTERISTIC

BMP will implemented effectively if community support. BMP technologies will require a certain amount of space of land owner at the upstream. As development grows, community will took chance to change land into impervious surface rather than stormwater BMP. Nevertheless, benefit of BMP implementation is directly taken by people who live at downstream. Therefore municipal authorities will have to look for ways to deal with both practical or policy from political standpoint and ecologically effective (Thurston 2006).

In policy study (CED UI 2008), the community of Sugutamu was grouped into three categories, based on area property unit: the first category has area property less than or equal to 90 sqm; the second category has property area between 90 to 150 sqm; and the third category has property area more than 150 sqm. Sugutamu individual choices of willingness to participate in stormwater management are listed at table 3 and based on community categories. Incentive mechanism that Sugutamu community chose is a reward, which is local government attention on public services improvement (Kurnia 2008; CED 2008).

Table 3. Compensation Individual Choice

Community Categories Participation

Unit Type I Unit Type II Unit Type III

Land and Fund Design and Technical-Specification

Contribute material Contribute human- resources

Contribute built-up

Contribute built-up

Design and Technical-Specification

Contribute material Contribute human-resources

Contribute built-up

Land Contribute built-up Contribute built-up



Contribute built-up



Community Categories Participation

Unit Type I Unit Type II Unit Type III

Fund Design and Technical-Specification


Contribute built-up

Contribute built-up



Contribute built-up

2.4 BMP ANALYSIS BASED ON AREA PROPERTY UNIT

Considering compensation that people chose, BMP is designed based on common practices. Proposed BMP on each area property unit characteristic that are: porous pavement, rain water harvesting, rain garden, and retention/detention ponds.

BMP will be set in impervious area. Category of area property unit is divided on three unit types where typical land properties are: full pavement, 90 percent paved, and 70 percent paved. On unit type I, there will be proposed porous pavement and simple rain water harvesting techniques. For area property type II, people will have more option that is porous pavement, rain water harvesting, and rain garden. The last, unit type III will implements porous pavement, rain water harvesting, rain garden, and retention/detention ponds.

Non-structural BMP that is proposed to the community is flood proofing. Local government could relocate housing along river banks. Then, people who live at high flood risk area need to be aware of flood hazard.

3. RESULTS

Basic hydrologic condition assumption is that all impervious area is connected. Then, runoff is controlled at the outlet. Design consideration of BMP base on controlling runoff volume and time concentration. Table 4.a and 4.b describes volume runoff that BMP controlled.

Table 4.a. Runoff Volume of BMP Area ave. category

area for each category

potential runoff vol.

m2

design ratio imp. site to

total

ratio each category

ratio imp. area to total (average)

m2 m3 90 1 0.36 0.65 1006200 10062

120 0.9 0.32 0.65 804960 8049.6 150 0.7 0.31 0.65 606515 6065.15

2795000 2417675

Using tools TR-55 and TR-20, if proposed BMP is installed then there will be runoff volume reduction as 27,5 percent. This modeling is done to acknowledge the consequence of BMP implementation on area property.



Table 4.b. Runoff Volume of BMP (continued)

BMP Type

Porous Pave.

Rain-water Harv. Rain Garden

Retention/ Detention Ponds

Volume BMP Total

BMP area

Inf. rate

Soak-ing

time Vol. Vol. BMP area

Inf. rate

Soak-ing

time Vol. BMP area Vol.

ratio m/h hours m3 m3 ratio m/h hours m3 ratio m3 m3 % 0.1 0.18 4 72446.4 100620 0 0.0127 4 0 0 100620 0.1 0.18 4 57957.12 80496 0,1 0.0127 4 4089.2 0 80496 0.1 0.18 4 43669.08 60651.5 0,1 0.0127 4 3081.1 0.1 60651.5

174073 241768 7170 241768 664778 27,5

4. CONCLUSIONS AND FUTURE WORK

By implementating BMP at Sugutamu, volume runoff at the outlet could be reduced. In practices, local government force to implement BMP design through local policy government (Peraturan Pemerintah Daerah or Perda).

5. ACKNOWLEDGMENTS

This research is a part of ongoing research Green Infrastructure by Design, Civil Engineering Department University of Indonesia.

6. REFERENCES

A Guidebook for British Columbia: Stormwater Planning, Ministry of Water, Land, and Air Protection, British Columbia, Canada, 2002. Chow, V. T.., Open-Channel Hydraulic International Student Edition, Mc Graw Hill Inc., United States of America, 1959. Chow, V. T., Maidment, D. R., and Mays, L.W., Applied Hydrology, International Edition, McGraw Hill Book Company, New York, 1988. Low Impact Development Manual, Prince George’s County Maryland, Department of Environment Resources, Maryland, 1999. Maidment, D. R., Handbook of Hydrology, Mc Graw Hill Inc., United States of America, 1993 Matteo, M., Randhir, T., and Bloniarz, D., “Watershed-Scale Impacts of Forest Buffers on Water Quality and Runoff in Urbanizing Environment”. Journal Water Resources Planning and Management; Vol.132, 2006, pp. 144-152, ASCE.

National Engineering Handbook: Section 4, SCS-USDA, 1964.



Thurston, H. W., “Opportunity Costs of Residential Best Management Practices for Stormwater Runoff Control”, Journal Water Resources Planning and Management; Vol.132, 2006, pp. 89-96, ASCE. Urban Hydrology for Small Watersheds, Technical Release 55, Department of Agriculture, Soil Conservation Service, United States, Washington, D.C., 1986.

Documents

BEST-MANAGEMENT-PRACTICES SELECTION STRATEGY IN …staff.ui.ac.id/system/files/users/dwita.sutjiningsih/publication/01hathi-manado-full... · Dwinanti Rika Marthanty, Dwita Sutjiningsih,