Conference PaperPDF Available

Gutter design and selection for roof rainwater catchment systems


Abstract and Figures

Water, while being critical for the survival of all of humanity, is not readily available to everyone. Within much of the developing world, water delivery systems are sub-par, leaving many homes without accessible and sustainable water resources. To address this issue, the use of rainwater harvesting systems is common. However, many extant systems are flawed in design, efficiency or sustainability. This paper investigates the impact of gutter cross-section on the performance and efficiency of rain water harvesting from roof catchments. Multiple gutter systems, with varying cross-sectional profiles, including a novel wrap-gutter design, were built and tested experimentally using a rainwater simulator. Experimental data, together with theoretical analyses, were used to rate gutter performance in terms of water lost though overflow, rate of water drainage, amount of standing water remaining in the gutter, amount of water loss via overshoot and the total amount of rain caught by the gutters. It was found that a wrap design, not normally highlighted in the literature, had the most consistent performance, regardless of rainfall intensity. Analyses regarding context-appropriate designs along with broader economic impacts of RWH systems are discussed.
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International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
Gutter Design and Business Development for Domestic
Rainwater Harvesting Systems: A Case Study
Jillian Zankowski
Community Environment & Development,
Environmental Resource Management
College of Agricultural Sciences
The Pennsylvania State University
Yixin Sun
Engineering Science
College of Engineering
The Pennsylvania State University
Abdalla Nassar
Applied Research Laboratory
The Pennsylvania State University
Khanjan Mehta*
Humanitarian Engineering and Social Entrepreneurship
The Pennsylvania State University
*Corresponding Author
Abstract - Rainwater harvesting is a simple and effective tool to collect and store water for
domestic and institutional use. In developing countries, captured rainwater can be used to
replace or supplement government-supplied or manually-transported water. A rainwater
harvesting system consists of a catchment area, gutter, and storage tank. Gutters typically
have a V-shaped, trapezoidal or rectangular cross-section. This work presents a case study
on the design and performance analysis of three conventional and one novel, “wrapped”
gutter cross-section along with the implementation of a novel gutter design in the
developing world. A Team of undergraduate students performed the design and analysis
and, though a service-learning experience in May 2013, investigated barriers to
implementing rainwater harvesting in central Kenya. It was found that while gutters can
be easily fabrication and installed using locally-available materials and skill-sets, for
consumer, the potential return on investment was low and the cost of implementation was
high. For producers and installers, non-uniform roof designs and conditions was a major
Index Terms - Rainwater harvesting; Catchment; Domestic; Roof Runoff; Water; Business
Within water-scarce areas, specifically those that have underdeveloped water infrastructure,
rainwater collection is a creative means of sustaining water sources and improving the quality of
life1. One of the most common practices is the use of rainwater harvesting (RWH), a technique
that aims to collect water running off roofs and other surfaces1. A rainwater harvesting system
normally consists of the catchment area, an attached gutter with mounting system, and a storage
area2. Systems vary most greatly in the cross-sectional design of their gutters. In a previous work3,
we experimentally assessed the performance of four gutter cross-section designs based on their
ability to intercept and convey water to a collection tank. We showed that, under heavy rainfall
conditions, a cross-section that wraps around the ends of the catchment area reduces losses due to
International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
water overshooting the gutter. But, due to leaks associated with its more complex connections, the
wrap design was second best under rainfall of less than 7 inches per hour. It was asserted that
using more watertight connections, the performance of the wrap design could have been
improved. This work seeks to explore issues associated with in-the-field implementation of this
and other RWH systems in the developing world, within a service-learning framework.
The service learning experience took place during May 2013 in Nyeri, Kenya, as part of a
humanitarian engineering and social entrepreneurship program at Penn State University. A team
of undergraduate students, majoring in both engineering and agricultural sciences, and under the
supervision of engineering faculties, sought to understand if and how novel gutter systems could
be implemented in the developing world; what barriers to entry exist for this and other gutter
designs; and, where would implementation of rainwater harvesting be most beneficial to users?
To answer these questions, students built multiple prototypes and installed them to typical roofs at
a children and youth center in the area, gathering data to determine the costs and tradeoffs
associated with rainwater harvesting.
Prior to detailing field-work activates and results, a brief overview of the laboratory work, used
to determine gutter performance is given in Section I. Following this, in section II, a description
of the fieldwork is provided, together with an analysis of barriers to implementing rainwater
harvesting in the developing world. This work serves as both as a case study of a project-based,
service-learning experience, which complemented classroom and laboratory study, to investigate
broader issues associated with technological innovation.
Material Selection
Rainwater harvesting gutter systems work successfully through the interaction of three basic
components: the catchment, delivery system, and storage reservoir4. Most critically, the
interaction between the catchment and the delivery system must convey water from the roof of a
home into the gutter system with minimal water lost. The total conveyance of a gutter system can
be calculated using Manning’s formula, shown in equation (1). This flow of water from the roof
(Q) is a function of the roughness coefficient of the gutter material (n), the cross-sectional area of
the gutter, (a), hydraulic radius of the gutter, (r), and the slope of the gutter following the roof,
 
Equation (1) can be used to compare the conveyance of different potential gutter materials,
using their roughness coefficients. Sheet metal is typically used due to its low roughness
coefficient (<0.015) and the ease with which it can be shaped. Moreover, sheet metal is readily
available in most of the developing world, including Kenya, where our fieldwork was conducted.
For these reasons, we used galvanized sheet metal to construct the gutters described here.
International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
Cross Section Design
While roughness dictated the materials used, cross-sectional area, a, had a greater impact on the
flow capacity of a gutter system, and thus the amount of water that could be collected and stored
within the storage tank. Cross-sectional area also directly impacts the performance of using a
gutter to collect rooftop runoff.
By compiling various data regarding flow rates and capacities of several gutter designs2,5, three
gutter designs, V-Shaped, Square, and Trapezoidal, were chosen for further examination. Through
the use of a rainwater simulator, we were able to determine the best gutter design for varying rain
intensities3. Along with V-Shaped, Trapezoidal, and Square gutters, a “wrap” design was
implemented during the second round of test trials. All cross-sections are shown in FIGURE 1,
copied, with permission, from Zankowski, et al., 2013.
In order to compare cross-sections, each cross-section prototype was installed onto a test roof and
placed under a rainwater simulator modeled after that described by Miller and Fennessey6.
Experiments were conducted to measure conveyance, conductance and interception characteristics
of the four different gutter designs. Interception refers to the act of water flowing off the roof
being caught by the gutter. Gutters were tested under rainfall intensities of 1 inch (2.54 cm) per
hour, 3 inches (7.62 cm) per hour, 7 inches (17.78 cm) per hour, and 9 inches (22.86 cm) per
hour, to replicate the variable rainfall of Nyeri, Kenya, where fieldwork took7. Each experiment
lasted 2 minutes, used to replicate the first wave of intense downpour during a storm8. Rainfall
caught within the gutters flowed into a cylinder, which was compared to the amount of rain which
fell onto the roof, or catchment area. Overshoot and percentage of rainfall caught could be
calculated in this way. Under 1 inch per hour, gutters were subjected to 0.5 gallons (1.9 L) of
water, 1.5 gallons (5.7 L) under 3 inches per hour, 3.5 gallons (13.2 L) under 7 inches per hour,
and 4.5 gallons (17 L) under 9 inches per hour. A 5 foot (1.5 m) high test roof, with a catchment
area of 24 ft2 (2.16 m2) and an angle of 15 degrees (FIGURE. 2), was used to mimic rooftops
within Kenya. The V-Shaped, Square and Trapezoidal cross-sections were hung from the jig,
while the wrap-design was attached directly to the roof. Further experimental details are discussed
in the authors’ previous work3.
International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
To compare the cross-sections, overflow, overshoot, the volume of standing water left in the
gutters, volume caught, and rate of draining were taken into account. Standing water refers to
water remaining inside the gutter after the rainfall. The amount of standing water was influenced
by the gutter’s longitudinal slope along the side of the building, as well as the length of the
building. To create a slope along the building, the distance from the roof to the bottom of the
gutter’s cross-section increased from one end of the gutter towards the downspout; longer
buildings thus would require flatter slopes. Volume caught refers to water, which fell onto the
roof, which was collected by the downspout during the rainfall, while rate of draining was
measured by the amount of time that has passed between the end of the rainwater simulation and
the cessation of water flow through the gutter. Data points in each category were weighted so as
to be comparable. TABLE I shows the weights assigned to each category, adding up to 1, to assess
total gutter performance. Weights were subjectively determined by the authors based on the
perceived importance of those criteria for the Kenyan context3. For full explanation of weighted
points and reciprocal evaluation, please see Appendix 1
Design Criteria
Standing Water
Caught vs. Lost
Rate of Draining
Total Score
International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
Laboratory data were collected for each cross-sectional design under 1 inch, 3 inches, 7 inches,
and 9 inches per hour. Within a typical year in Kenya, rainfall intensity is 1 inch per hour or
less9. Thus for the remainder of the paper, data collected at a rainfall intensity of 1 inch per hour
are used in evaluating performance and economy. Weighted performance data for this intensity,
including overflow, drainage, standing water, overshoot and total rain caught, can be found in
TABLE II. To be clear, these are not raw data, but weighted (dimensionless) values based on the
weights assigned in TABLE I. Raw data are available in the authors’ previous work3.
V Shape
While overflow was not observed in any instance, overshoot was a common problem.
Overshoot of the gutter increased with rainfall intensity. Though the wrap design (shown in
FIGURE. 3) did surround the edge of the roof, gaps between the gutter and the roof caused
leakage. This water loss was attributed to overshoot, since it was a measure of the gutter’s ability
to intercept the water flowing from the roof. Watertight connections would significantly enhance
the gutter’s overshoot performance.
The weighted performance data, presented in TABLE II allows comparison of each gutter
across our design criteria. A sum of performance values across all criteria was used to compare
overall performance of gutter cross-sections under different rainfall intensities. Final results
International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
comparing performance of gutter cross-sections for different rainfall intensities are shown in
Rainfall Intensity
1 in/hr
3 in/hr
7 in/hr
9 in/hr
Though a trapezoidal gutter cross-section was determined to be the best fit for rainfall
conditions at, or below, 3 inches per hour, the wrap design was chosen for field-testing in Kenya
for two reasons. One, the wrap design’s underperformance with respect to overshoot was viewed
as improvable with watertight connectivity. Two, although rare, rainfall intensity above 3 inches
per hour does occur and results in a significant rainfall that can be captured9. Field research was
focused on determining the feasibility of using this design on non-uniform roofs in the Kenyan
context and the feasibility of implementing a more complex, though more efficient, gutter design.
During May 2013, fieldwork was done in Kenya to test both the feasibility of local construction of
the rainwater harvesting system (RWH), as well as to investigate the economics of rainwater
harvesting in Nyeri, Kenya. Due to limited time and resources, only the wrap design was field
tested in Nyeri. This section will discuss the barriers to adoption of RWH technologies within
Kenya, with particular emphasis on feasibility of a cost-efficient system, the value proposition to
both producer and consumer, and the scalability of such a RWH business venture. Barriers to
entry were found specifically with regard to return on investment due to higher installation costs,
compared to locally available options, as well as the availability of government supplied water.
These issues are discussed through the use of an efficiency analysis, with regard to water caught
over time, and a cost analysis, taking given efficiencies and the time until the gutter system
become profitable.
Cost and efficiency analysis
Efficiency analysis
Rainwater harvesting systems tend to be sold by the foot, or meter, within the Nyeri market, as is
common within the developing world context. In order for a rainwater harvesting system to be
cost-effective, the system must cost less than, or equal to, the cost of water, over its lifetime.
Thus, determination of cost-effectiveness requires knowledge of average rainfall, material cost
and calculation of gutter efficiency.
First, the efficiency of the gutter, with regard to price, can be calculated using raw material
costs as found in Nyeri. The efficiencies of each gutter can be determined through Equation (2).
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ISSN 1555-9033
  
 (2)
TABLE IV compares the efficiency of four gutter designs assuming a rainfall of 1 inch per
hour, and a 400 ft2 (37 m2) roof. This roof area is comparable to ones found in small schools,
strip malls, and similar structures in Kenya. For example, the manager of the Children and Youth
Empowerment Center (CYEC) in Nyeri, Kenya, estimated that nearly 2000 gallons (7570 L) of
water was purchased by the center from the government each month. Based on this, the hours of
rainfall needed was calculated using Equation (3), with M representing the number of hours of
rainfall needed in order to match the 2,000 gallons used per month. At a rainfall intensity of 1
inch per hour, 33.3 cubic feet, or 249.33 gallons fall on the roof each hour. The hours of rainfall
necessary, per month, to meet the total consumption needs of the CYEC are given in TABLE IV.
    (3)
Hours of continuous
rainfall to reach 2000
V Shape
Based on the values in TABLE IV, the ranges of rain needed for each system to store enough
water to replace that purchased from the government is between 9.00 and 10.62 inches. While
seemingly small, the wettest month of the year, April, only produces 7.7 inches of rain on
average9. It is therefore impossible to collect sufficient rain to meet monthly needs. Hence,
harvested rainwater is unlikely to replace purchased water. A rainwater harvesting system may
however be used as a supplemental water delivery system, and can save money over time by
decreasing the need to rely on purchased water.
Cost analysis
Consumers want to buy the least expensive and most durable product for their home or business.
Within the developing world context, cost is a primary driving factor. TABLE V compares the
prices of different gutters per 6-foot sections, based on raw materials and tools needed. In
calculating the values shown in TABLE V, it was assumed that the gutters are attached to a 20 ft x
20 ft roof, typical of large institutions surveyed in Nyeri, Kenya, requiring 80 feet of gutter. It
may be noted that 80 ft is an over estimate, as many institutions use a gable or skillion roof rather
than a pyramid-shaped roof. It was also assumed that 650 Kenyan shillings (KES) will be spent
for a tank--this figure is based on a survey of shop owners within the market of Nyeri, Kenya.
International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
The cost of a full 80-foot system can be estimated by calculating the cost of 80 feet of gutter and
then adding the cost of the tank. These prices were used to determine how many hours of
rainfall, at a relatively strong rainfall intensity of 1 inch per hour9, would be needed to recoup the
capital costs (i.e. return on investment). Payback periods can be seen in TABLE V.
Gutter Type
Price per 6
feet (KES)
Price per
Hours of rain until Break
V Shape
Assuming that water costs 2,000 KES per month for an average local institution, it would take
over a day of continuous rainfall or more than 28 inches of rain for the gutter systems to make
back their investment in full. Even when spread out over the course of a month, it is highly
unlikely that sufficient rainfall events would occur in an arid or semi-arid environment,
particularly in the dry season. Simply put, there are cheaper options available to obtain clean
water other than a RWH system.
Barriers to Entry
Standardization Barrier
One of the fundamental objectives of this rainwater harvesting project was to standardize gutter
design and installation. However, our fieldwork demonstrated that this approach is inherently
problematic. In Nyeri, Kenya, and much of the developing world, roofs are not standardized
(FIGURE. 4), and thus anything attached to them has to be altered to account for unique roof
International Journal for Service Learning in Engineering
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ISSN 1555-9033
For one, materials used to make roofs vary considerably. In cities, most rooftops are
constructed with corrugated metal sheet in flat, skillion (or lean-to), and hipped shapes. In rural
areas, where people do not have access to sheet metal, rooftops are constructed with lumber,
leaves, straw, and newspaper. Practically, metal-gutter-based rainwater harvesting systems can
only be attached on the skillion or fascia board and hipped roofs made of sheet metal. This
implies that rural areas, where the need for water is greatest, cannot be supplied easily. Secondly,
there is no standard for the slope of the roof and the distance between the edge of the roof and
the wall. Since our wrap design is dependent on the slope of the roof and the distance between
the edge of the roof and the wall, customizing the gutter design is crucial and inevitable. Thus,
mass manufacturing, which can drastically reduce overhead costs cannot be easily employed.
Moreover, lack of maintenance is a common problem in both rural and urban areas, contributing
to rusted and fragile roofs that are not strong enough to attach gutter systems.
Value proposition challenges
To justify the expense of the gutter, its primary purpose of collecting and storing rainwater has to
be the main goal of the consumer. Within the parts of Kenya in which government water delivery
is available, there is no need to collect rainwater for domestic use. Government-supplied water is
also widely available in the more developed areas, which coincide with areas that receive periods
of heavy rainfall and have many available bodies of water. Bodies of water, including streams,
rivers, and lakes, are used when there is a need for more water than what the government is
providing through taps. Thus, the need for an additional water source is nonexistent. Informal
interviews with locals indicated that these regions tend to use gutters to keep water from running
down exterior building walls to prevent them from decaying. In this instance, a wrap design
would provide the most benefit, since, when installed correctly, no gaps occur between the gutter
and the wall of the building, allowing minimal water to escape.
In other contexts, such as Northern regions of Kenya, where water is scarcer, drought is a
common occurrence. Schools and households in Kenya struggle to continually have enough
water to keep their facilities running. Throughout Kenya, while there are 55 water service
providers, only 7 of them offer continual service, including Nyeri, where our research took
place10. For the areas under the other 48 water service providers, rainwater harvesting would be
beneficial. However, medium and large institutions require much larger amounts of water than
International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
what can be provided by domestic rainwater systems. In order to meet 2000 gallons of water
needed based on the previous assumption, massive catchment systems would have to be
installed. Unfortunately, such massive systems require the institution to have access to
significant financial capital and long-term maintenance.
While not all areas of Kenya have access to government-supplied water, those that do not tend
to be in arid areas that have less than less than 14 inches of rain over the year11. In these regions,
water bodies are the primary sources of water. Though residents may need to travel long
distances to get to these bodies of water, there is a lack of other employment; so wasted time
does not mean wasted money. Thus, the rainwater harvesting system can save time for local
people, but they do not see the value, and the value proposition fails. While there is a need for an
additional water source within the area, domestic rainwater harvesting does not provide the right
answer, since there is little rainwater to be harvested.
The value proposition for the entrepreneur is fundamentally connected to the value created by
the product for potential customers. Within the central Kenyan market, customers we
interviewed did not find inherent value in installing rainwater harvesting systems on their roofs.
The value of the product is hard to justify. At the same time, due to the non-uniformity of each
roof, each gutter needs to be customized based on the slope of the roof and the distance between
the edge of the roof and the wall. This leads to higher costs and makes the product even less
marketable. Thus, mass manufacturing is not possible and the installation process would need to
be customized to every roof, requiring a trained cohort of workers. In essence, a business that
installs domestic rainwater harvesting systems is not a lucrative venture under current conditions
and municipal water costs.
Initially, the student team set out to design an efficient domestic rainwater harvesting systems to
address the need for affordable, reliable and sustainable water sources in developing countries
likes Kenya. Towards this end, a three-tiered approach was used. First, a laboratory analysis of
the performance of four gutter cross-sections was conducted to assess the performance of three
conventional and one novel gutter designs under rainfall between 1 and 9 inches per hour. Next,
an analysis of the costs, benefits and challenges to implementations of a rainwater harvesting
system, based on fieldwork in central Kenya, was conducted. Finally, economic and laboratory
results were compared to determine the value and feasibility of a rainwater harvesting venture in
While the ability to procure material, fabricate and install gutter systems was easily validated
in Nyeri, Kenya, economic barriers and value proposition challenges emerged as main obstacles.
A key challenge is the cost of the rainwater harvesting system. In areas where rainfall intensities
are sufficient to enable consumers to collect enough water to meet their needs, inexpensive
(utility-supplied) or free (manually-transported) water is available. Furthermore, conversations
with consumers revealed that they purchased gutters to protect exterior walls from water damage,
not for rainwater harvesting. Coincidentally, the communities in need of sustainable and reliable
water delivery lacked access to capital and were not capable of recouping their capital costs in a
short term due to the lack of rain in their area. While the laboratory results behind our design
holds strong, it does not serve as a viable platform for a successful business.
Potentially, one can still implement the proposed wrap design in a different context, with a
unique entrepreneurial approach, to help alleviate water scarcity. Non-profits can use the design
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to enhance the efficiency of the rainwater harvesting system donated to help local communities.
For-profit businesses can implement the design in urban areas, where people have more
disposable income to invest in a rainwater harvesting system.
Ultimately, however, this work serves as a case study that illuminates the challenges
associated with implementation of rainwater harvesting systems in the developing world. Though
it may be argued that some implementation challenges, such as inconsistent roof designs, should
have been obvious to the student team without fieldwork, the fieldwork proved to be the critical
factor in understanding the complexities of applying engineering solutions in the developing
world. Informal interviews with locals allowed generation of realistic pricing and water
consumption data. First-hand experience installing gutters allowed students to understand the
difficulties associated with installation of a gutter on rusty, non-uniform roof. Soliciting the
views of local vendors, homeowners and managers of institutions allowed students to better
appreciate that though the design may work, individuals will not purchase an item they don’t see
as cost efficient or beneficial. Through this service learning experience, students were able to
better appreciate engineering design and its real-world considerations, as well as the broader
We would like to acknowledge Dr. James Hamlett for generously allowing us to use his
rainwater simulator and assisting us in data collection and analysis. Thank you to Chiyan Poon
and Emily Passauer, who helped in data collection. We would also like to thank Tara Sulewski,
Liz Kisenwether, Susan Beyerle, Andras Gordon and Irene Mena for mentoring several freshmen
design teams that collectively inspired our team to explore various gutter designs and installation
methods. Lastly, thank you to those that made our fieldwork possible through scholarship and
awards, particularly Penn State’s Undergraduate Research Exhibition judges, who awarded us
the Gerard A. Hauser award, contributing to our research funds.
1 Sazakli, E., Alexopoulos, A., & Leotsinidis, M. (2007). Rainwater harvesting, quality
assessment and utilization in Kefalonia Island, Greece. Water Research, 2039-2047.
2 Still, G., & Thomas, T. (December 2002). The Optimum Sizing of Gutters for Domestic
Roofwater Harvesting. Research Report, University of Warwick, School of Engineering.
3 Zankowski, J., Sun, Y., Poon, F., Passauer, E., Nassar, A., & Mehta, K. (2013). Gutter Design
and Selection for Roof Rainwater Catchment. IEEE Global Humanitarian Technology
Conference. San Jose, CA.
4 Worm, J., & van Hattum, T. (2006). Rainwater Harvesting for Domestic Use. Wageningen, The
Netherlands: Agromisa Foundation.
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5 Hatibu, N., Mutabazi, K., Senkondo, E., & Msangi, A. (2006). Economics of rainwater
harvesting for crop enterprises in semi-arid areas of East Africa. Agricultural Water
Management, 80(1-3), 7486.
6 Fennessey, L. A., Miller, A. C., & Hamlett, J. M. (2001, August). Accuracy and precision of
NRCS models for small watersheds. Journal of the American Water Resources Association,
37(4), 899-912.
7 The World Factbook. (2013, April 9). (Central Intelligence Agency) Retrieved April 16, 2013,
8 Homebuilding, F. (2005). Roofing: Flashing & Waterproofing. Newtown, Connecticut, USA:
The Taunton Press.
9 World Weather Online. (2013). World Weather Online. Retrieved November 18, 2013, from
10 WASREB. (2009). Water Service Quality - WASREB Impact Report 2009. Kenya: WASREB.
11 Community Adaptation and Sustainable Livelihoods. (n.d.). Arid and Semi-Arid Lands:
Characteristics and Importance. Retrieved November 11, 2013, from International Institute for
Sustainable Development:
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Methodology of rainfall simulation, from Gutter Design and Selection for Roof Rainwater
Catchment 3
Experiments were conducted on a rainwater simulator that was modeled after the simulator
described by Miller and Fennessey.6 The simulator was used to test conveyance, conductance and
interception characteristics of the four different gutter designs (FIGURE. 1). Rainfall intensities
were described as “light”, “moderate”, “heavy”, and “violent”, with rainfalls of 1 inch per hour, 3
inches per hour, 7 inches per hour, and 9 inches per hour, respectively. Note that use of these
descriptors of rainfall intensities are only intended to be descriptive for the purposes of this paper
and not standardized as in Still and Thomas.2 The duration of each experiment was 2 minutes.
Such a short experimentation time was used to mimic the first wave of intense downpour during a
storm.8 This normally occurs within the first 5 minutes, but due to time constraints, 2 minutes was
used. During this time, rainfall was captured in a calibrated graduated cylinder. Rainfall intensity
was determined by dividing the total amount captured in the cylinder by the duration of the
experiment (1/30) hours. It may be noted that increasing the duration of the experiment from 2 to
3 minutes did not affect the gutter performance results.
A 5 foot high test roof (Fig. 2), angled at 30 degrees, and with a 4 ft by 6 ft corrugated metal
sheet secured on top was used to simulate a roof catchment. The total catchment area was 24 ft2.
The ‘V’ Shaped, Square and Trapezoidal gutters were suspended from the roof catchment using
steel wire hung from an iron rod. The wrap gutter, however, was attached using nuts and bolts
every 1.2 meters. During the light, moderate, heavy, and violent rainfalls, each gutter was
subjected to 1.89L, 5.66L, 13.21L, and 16.99 L of water over 2 minute duration of each
experiment, respectively. This volume was calculated based on roof area, roof angle and rainfall
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Collected data reflected the amount of water lost through overflow, rate of water drainage,
amount of standing water remaining in the gutter, amount of water lost via overshoot and the total
amount of rain caught by the gutters. Overflow was defined as the volume of water that exceeded
the volume of the gutter, and spill out of the gutter, measured by the liters of water collected from
the gutter’s downstream. Rate of drainage was defined as the elapsed time after rainfall had
stopped and the flow from the gutter stopped. Standing water was the volume of water remaining
in the gutter after all flow had ceased, measured in milliliter. These measured values characterized
the conveyance of each gutter system. Once raw data were collected for each gutter and rainfall
intensity, they were ranked against each other and then multiplied by their weighted rates shown
in Table VI. Weights in Table VI were determined based on our assessment of criteria important
for success of a gutter system in and around Nairobi, Kenya. Readers are encouraged to design
their own scoring matrix based on their specific context.
Design Criteria
Standing Water
Caught vs. Lost
Rate of Draining
Total Score
International Journal for Service Learning in Engineering
Vol. 9, No. 1, pp. 64-78, Spring 2014
ISSN 1555-9033
Ranking was accomplished by normalizing the reciprocals within a given data set (e.g.
overflow, rate of draining, etc.), with 1 being equal to the smallest reciprocal. For instance, if A,
B, C and D are measured, scalar values of some property, each respective reciprocal was scaled
such that
c × min{1/A, 1/B, 1/C, 1/D}=1
Next, the scaled quantities, {c/A, c/B. c/C, c/D}, where c is the scaling coefficient, were
multiplied by the weight for the measured data set, given in Table VI. The resulting data was
termed weighted data.
Radar plots juxtaposed weighted data for each gutter design. This allowed determination of the
best gutter for each rainfall intensity. Note that the scoring matrix shown in Table VI is
subjective and based on the importance of each criteria within the context in which the RWH
system is expected to be used. Additionally, it should be noted that experiments were conducted
under laboratory conditions, where environmental factors such as wind, rusting and roof
deformation were not accounted for. These factors may ultimately prove important in real-world
... The system can also monitor the quality of water using methods such as turbidity detection, dissolved oxygen/PH/humidity/temperature measurements, besides others. [5] presents a system designed to collect rainwater and use it for recycling. In [6] one can find a review of smart metering and intelligent water networks in Australia and New Zeland. ...
According to UNESCO, with the existing climate change scenario, by 2030, water scarcity in some arid and semiarid places will displace between 24 million and 700 million people. In India, the paucity of water is increasing every year in a drastic way and so does the demand. This has occurred as a result of deficient planning and inappropriate management of water resources. Surface water and groundwater, which constitute approximately 40% of total precipitation, are two major sources of drinking water. It is evident that the collection of rainwater is very pivotal and beneficial. This paper illustrates the idea of conserving rainwater in an economic and renewable way by occupying free space and compact arrangement. This stand-alone system also focuses on automatic functioning of system using IoT.
This work introduces a classroom strategy which leads university students to solve real world and challenging problems. The basic hypothesis is that technology does not need to be complex or state-of-the-art to be helpful. Basic knowledge of mechanics, electronics and computation is enough to solve a need and provide simple yet useful, products. The case herein presented is about a classroom of students who are currently working on social-technological projects. They are collaborating with Multiple Attention Center (CAM), which serves children with all types of special needs, such as motility problems, cerebral palsy, language problems, blindness or deafness. The goal is simple: provide a solution for one person at the CAM. The students, organized in teams, were offered +10% on their final grade for the design and manufacture of a product that helps one person at the CAM. As a result of this offer, 10 different products were developed, such as a special mouse with a large joystick and a software interface to communicate basic needs, developed for children affected with cerebral palsy, and a blow-training device for children with language problems. It is important to recall that each project is customized and unique for a person at the CAM, which becomes attractive for students involvement, but not for commercial purposes. Teachers at the CAM have been involved with the requirements definition for the products and will provide their evaluation. These projects also fulfill three relevant objectives for the engineering students: To use knowledge to implement a real-life solution, to make them aware that they can change a life with a little bit of technology, and to bring them face to face with different realities other than the one at their private university. This strategy can be easily employed to reach more people with little monetary investment and significant satisfaction.
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The quality of harvested rainwater which is used for domestic and drinking purposes in the northern area of Kefalonia Island in SW Greece and the factors affecting it were assessed through 3-year surveillance. In 12 seasonal samplings, 156 rainwater and 144 ground- or mixed water samples were collected from ferroconcrete storage tanks (300-1000 m3 capacity), which are adjacent to cement-paved catchment areas (600-3000 m2). Common anions and major cations as well as the metals Fe, Mn, Cd, Pb, Cu, Cr, Ni and Zn were tested. The presence of three major groups of organic compounds, polycyclic aromatic hydrocarbons (PAHs), organochloride pesticides (OCPs) and volatile organic compounds (VOCs), was screened by common analytical techniques. All of the rainwater samples were within the guidelines for chemical parameters established by the 98/93/EU directive. As far as microbiological quality is concerned, total coliforms, Escherichia coli and enterococci were detected in 80.3%, 40.9% and 28.8% of the rainwater samples, respectively, although they were found in low concentrations. Chemical and microbiological parameters showed seasonal fluctuations. Principal component analysis revealed that microbiological parameters were affected mainly by the cleanness level of catchment areas, while chemical parameters were influenced by the sea proximity and human activities. Disinfection should be applied into the tanker trucks which distribute the water to the consumers and not into the big storage tanks in order to avoid by-products formation. Due to the lack of fluoride in rainwater samples, the consumers must become aware of the fact that the supplementation of this element is needed.
Zimbabwe's poor are predominantly located in the semi-arid regions (Bird and Shepherd, 2003) and rely on rainfed agriculture for their subsistence. Decline in productivity, scarcity of arable land, irrigation expansion limitations, erratic rainfall and frequent dry spells, among others cause food scarcity. The challenge faced by small-scale farmers is to enhance water productivity of rainfed agriculture by mitigating intra-seasonal dry spells (ISDS) through the adoption of new technologies such as rainwater harvesting (RWH). The paper analyses the agro-hydrological functions of RWH and assesses its impacts (at field scale) on the crop yield gap as well as the Transpirational Water Productivity (WPT). The survey in six districts of the semi-arid Zimbabwe suggests that three parameters (water source, primary use and storage capacity) can help differentiate storage-type-RWH systems from "conventional dams". The Agricultural Production Simulator Model (APSIM) was used to simulate seven different treatments (Control, RWH, Manure, Manure + RWH, Inorganic Nitrogen and Inorganic Nitrogen + RWH) for 30 years on alfisol deep sand, assuming no fertiliser carry over effect from season to season. The combined use of inorganic fertiliser and RWH is the only treatment that closes the yield gap. Supplemental irrigation alone not only reduces the risks of complete crop failure (from 20% down to 7% on average) for all the treatments but also enhances WPT (from 1.75 kg m -3 up to 2.3 kg m-3 on average) by mitigating ISDS.
Considering the persistently growing pressure on finite freshwater and soil resources, it becomes increas- ingly clear that the challenge of feeding tomorrow's world population is, to a large extent, about improved water productivity within present land use. Rain-fed agriculture plays a critical role in this respect. Eighty per cent of the agricultural land world- wide is under rain-fed agriculture, with generally low yield levels and high on-farm water losses. This suggests a significant window of opportunity for improvements. Ninety-five per cent of current popula- tion growth occurs in developing countries and a significant proportion of these people still depend on a predominantly rain-fed-based rural economy. This chapter presents the agrohydrological rationale for focusing on water productivity in rain-fed agriculture, identifies key management challenges in attempts to upgrade rain-fed agriculture and pre- sents a set of field experiences on system options for increased water productivity in smallholder farm- ing in drought-prone environments. Implications for watershed management are discussed, and the links between water productivity for food and securing an adequate flow of water to sustain ecosystem services are briefly analysed. The focus is on sub-Saharan Africa, which faces the largest food-deficit and water-scarcity challenges. The chapter shows that there are no agrohydrological limitations to doubling or even quadrupling on- farm staple-food yields, even in drought-prone environments, by producing more 'crop per drop' of rain. Field evidence is presented suggesting that meteorological dry spells are an important cause of low yield levels. It is hypothesized that these dry spells constitute a core driving force behind farmers' risk-aver- sion strategies. Risk aversion also contributes to the urgent soil-fertility deficits resulting from insignifi- cant investments in fertilizers. For many smallholder farmers in the semi-arid tropics, it is simply not
This paper was associated with a WARFSA funded research project ''Potential of rainwater harvesting in urban Zambia''. The general objective of the research was to investigate the applicability of rainwater harvesting in urban Zambia. This paper presents the results obtained at the time of writing the paper. Rainwater harvesting was not new to Zambia and there had been installations which were mainly confined to rural areas. Laboratory analysis of water samples from one such system showed that the water was suitable for drinking purposes. Two peri-urban areas of Lusaka were selected mainly based on the water stress in the areas. The socio-cultural survey conducted in the two areas indicated that water ranked among the top two priorities by the Residential Development Committee. Design of the systems was based on the mass curve analysis for storage and rational formula for the gutters. However, a maximum storage of 10 cubic meters was chosen due to budgetary limitation. Construction of five systems was in progress.
In the last 30 years, the National Resource Conservation Service's TR-55 and TR-20 models have seen a dramatic increase in use for stormwater management purposes. This paper reviews some of the data that were originally used to develop these models and tests how well the models estimate annual series peak runoff rates for the same watersheds using longer historical data record lengths. The paper also explores differences between TR-55 and TR-20 peak runoff rate estimates and time of concentration methods. It was found that of the 37 watersheds tested, 25 were either over- or under-predicting the actual historical watershed runoff rates by more than 30 percent. The results of this study indicate that these NRCS models should not be used to model small wooded watersheds less than 20 acres. This would be especially true if the watershed consisted of an area without a clearly defined outlet channel. This study also supports the need for regulators to allow educated hydrologists to alter pre-packaged model parameters or results more easily than is currently permitted.
This paper presents an analysis of economics of rainwater harvesting by poor farmers in Tanzania. A questionnaire was used to survey 120 households to obtain information on the performance of their enterprises over 6 years (1998–2003). The information was mainly based on recollection as few farmers kept detailed records. Actual monitoring and measurements of yield and inputs was done in the farmers’ enterprises over 2 years during 2002/2003 and 2003/2004 production seasons. The analysis was done for four categories of rainwater harvesting systems differentiated by the size of catchments from which water is collected and the intensity of concentration and/or storage of the collected rainwater. These categories are: micro-catchments, macro-catchments, macro-catchments linked to road drainage and micro or macro-catchments with a storage pond. Results show that rainwater harvesting for production of paddy rice paid most with returns to labor of more than 12 US$ per person-day invested. These benefits are very high due to the fact that without rainwater harvesting it is not possible to produce paddy in the study area and rainfed sorghum crop realizes a return to labor of only US$ 3.7 per person-day during above-average seasons. For the rainwater harvesting systems, those designed to collect water from macro-catchments linked to road drainage, performed best during both categories of seasons. The results also show that contrary to expectations, improving rainwater harvesting systems by adding a storage pond may not lead to increased productivity. Another finding that goes against the widely held belief is that rainwater harvesting results in more benefits during the above-average seasons compared to below-average seasons. It is therefore, concluded that there is a potential for combining rainwater harvesting with improved drainage of roads. The construction of rural roads in semi-arid areas can beneficially be integrated with efforts to increase water availability for agricultural needs.
Although rainwater harvesting system (RHS) is an effective alternative to water supply, its efficiency is often heavily influenced by temporal distribution of rainfall and water demand. Since natural precipitation is a random process and has probabilistic characteristics, it will be more appropriate to describe these probabilistic features of rainfall and its relationship with design storage capacity as well as supply deficit of RHS. This paper aims at developing a methodology for establishing the probabilistic relationship between storage capacities and deficit rates of RHS. A simulation model was built to simulate the input rainfall and water release in RHS. Historical rainfall records were then used as input for simulation and the results were used in probabilistic analysis for establishing the relationships between storage capacities and water supply deficits. The city of Taipei was used as study area for demonstration of this methodology and probabilistic distribution curves for storage capacity and deficit rate relationships were presented. As a result, a set of curves describing the continuous relationships between storage capacities and deficit rates under different exceedance probabilities were generated as references to RHS storage design. At a chose exceedance probability of failure, the engineer can decide from the curve on the storage size under a preset deficit rate.
Roofing: Flashing & Waterproofing
  • K Ireton
  • Fine Homebuilding
K. Ireton, Fine Homebuilding, "Roofing: Flashing & Waterproofing".