Storm Water Management - Science topic

Generally the flood or water managers would prefer customised tools because off the shelf software cannot provide for the heterogeneities of soil water behaviours and then to incorporate the stakeholder expectations. As most flood management institutions do not have sufficient inhouse experts, these customisation tasks are outsourced and new products are developed on Contract. However such products or details of product development or the utilisation of such products do not get reported since they are not public domain information (have copyrights). Unconfirmed information is that such customisations do not lead to sustainable continued products due to development issues, contractual issues, maintenance agreement issues etc. Hence instead of developing sustainable tools by learning from others, most tools use off-the-shelf application software and then reinvent the wheel. This individual and independent reinventing efforts lead to unproductive work and hence, poorly contribute to the efforts of flood and water management. We all should try to get the customisation efforts into light and capture the reason for unsuccessfulness of such customisations. or unsustainability of such customisations.

Dear Nzeyimana,

Check this out for stormwater management https://www.epa.gov/water-research/storm-water-management-model-swmm

regarding climate change it depends on how you would approach it, e.g. it can be considered in a separate module and inserted as an input in the swmm. But in any case there are some such free applications online if you search on the internet.

Hope this helps,

Angelos

Dear Bhupesh

If you are designing a storm water system then you need to estimate the “critical storm duration” for each storm water catchment. The "critical storm duration" is the storm duration of a specific return period storm event (e.g., 2, 5, 10, 25, 50, 100 years) which generates the highest flow in the storm water drainage system.

The critical storm duration is related to the catchment characteristics. Generally the larger the catchment area the longer the critical storm duration, although other factors such as the slope and impervious area of the catchment also have an effect.

In some regions of the world drainage authorities have formulae which define a first estimate of the critical storm duration. In some cases "trial and error" methods are used, for example, a rainfall-runoff model will be run with a number of different storm durations and the storm duration that generates the largest flow for the catchment draining to the discharge point into the storm water network will be deemed to be the "critical storm duration".

I hope that this is of help.

Best regards

Darren

You can follow some reference materials and refer to how others do their process. Attached is my team's methodology of the building of the pilot and field scaled systems for the urban stormwater runoff. In this study, we used a bioretention tree system for the treatment of urban roof runoff.

The Annual Maximum Series, (AMS) rainfall amount measured 24 hourly (daily) can be reduced to shorter duration of 0.166, 0.1333, 0.5, 1, 2,...hours as may be required for analysis. Rainfall values (shorter duration) can be obtained via Indian Meteorological Dept. (IMD) empirical formula for reduction proposed by Ramaseshan (1996) as given below:

Try good ol' Fogler http://www.umich.edu/~essen/html/byconcept/chapter13.pdf

A few ideas. The size of basin with respect to drainage area and expected storm flow. The residence time for suspended solids to settle before discharge. The length or path distance that sediment would have to move within the sediment basin before being discharged. The type of sediments - storing clays is especially difficult to settle without sufficient storage time. Maintenance of sediment basin - will it be maintained on regular schedule, or just built and left. Sediment sources and activities in watershed. If capacity is exceeded, would the sediment basin fail or have emergency overflow? How long is sediment basin supposed to operate, short term associated with an activity and mitigation, or long term due to recurrent sediment issues and need for low sediment to support downstream uses, water treatment, etc. Consider type of upstream contributing streams - gullies and steep gradients deliver sediments efficiently, while upstream braided streams are result of high sediment load, and they also tend to be accumulating sediment (aggrading). What is potential for contributing upstream activities such as channelization, road development and land clearing, urbanization, etc. If not familiar with Roehl (about 1962), he developed sediment delivery ratio from drainage size using ponds and dams. His results suggest that the larger the contributing drainage area and associated reservoir, the greater efficiency at removing sediments, and one might also assume that larger watersheds often have ability to store some sediment on their floodplains.

Happy to read good points, but the magnitude of the differences reached with this approximation with respect to the real conditions further needs elaboration with examples.

For example German Design guideline ATV‐A 128

• design principle: lCOD,CSO <= lCOD,RW

• applicable for small, simple networks

• more complex systems: hydrologic / dydrodynamic modelling

• relevant factors of influence on CSO volume and concentration:

regional and site factors:

• precipitation

• contentration time

• slope

• storage capacity

• heavy polluters

typical design case:

• annual precipitation

• cCOD in stormwater

• cCOD in wastewater

• cCOD in wwtp effluent

Have a look at https://www.epa.gov/water-research/storm-water-management-model-swmm to see the capability of the SWMM program package. Exploitation of such a package is reasonable in solving complex tasks on big catchments. It will provide much more detailed insight into the behavior of the catchment than the use of  analytical expressions and empirical formulas. However, the cost is in the quantity and quality of the required input data.

The best approach is using the simplest tool up to the task considered.

Regards, Julius

Thank you very much for the answers so far and the publications I've received both here and privately!

Antonio, I am working with data from separate sewer systems and I have water quality data from rainfall (and snowmelt) periods (=wet weather) and from the baseflow between events (=dry weather). I am not sure yet what to do with my data, but I want to experiment with SWMM and try its water quality modeling component. Just a note regarding your question (although I am not familiar with combined systems): In Finland we have a rather low proportion of combined systems (less than 10% of the total length of pipe sewer systems). Here since about 1970's separate systems became the main type of sewer systems - this was a good solution because we have avoided the CSO problems of more southern Europe where combined systems are much more common. However, I think it's becoming more and more evident that even runoff from separate sewer systems should not be conveyed untreated to receiving waters. Probably the best solution for this is the development of LID/SUDS systems for stormwater runoff. In a cold climate such as Finland, a big issue with combined systems is that the cold snowmelt runoff during spring disturbs the treatment processes at wastewater treatment plants.

Thanks to all of you for your very intresting and useful suggestions.

They will help me to improve my model by understanding its weak points.

Thanks WIlliam and MET means Metal Trace Elements. Effectively smal samples can not represent the trend of contaminants and we are looking for a factor to estimate the range of contaminants concentrations. Such factor are used by company in charge of used and collected waters (some used a factor of 8) but we have not scientific evidence of suc factor

I used this sites:

Timothy Randhir--Thank you.  Our interest is in a traditional triple bottom line approach, so income/race and other criteria do play a role depending on the jurisdiction.  We have considered use of SPSS on the same.  Your response was appreciated.

if the rainfall depth of the 3 hrs is uniformly distributed. You can simply divide the rainfall depth collected over 3 hrs. by 3. So you get the rainfall depth by 1 hr. 

Thanks Dear Ljubomir and Dear Mohan for the pertinent links selected. According to one of the links that Ljubomir selected “Estimating Storm Water Runoff” from 2012, by John Poullain (PE):

“Limitations of the Formula: The major limitation is that the Rational Formula only produces one point on the runoff hydrograph--the peak discharge rate. When basins become complex, and where sub-basins combine, the Rational Formula will tend to overestimate the actual flow. The over estimation will result in the oversizing of stormwater management systems.”

In fact I obtained results in the opposite direction. The classic Rational Method is a kinematic method (i.e., it assumes that the maximum flow occurs when whole upstream drainage basin is contributing for the formation of the flow in the sewer section, for a time of precipitation, Tp, equal to the time of the concentration of the basin in that section, Tc), assuming implicitly a symmetric triangular hydrograph of base 2Tc. The intensity of precipitation decreases, in the curves of Intensity-Duration-Frequency (IDF curves), for a given Period of Return, TR, when the time of precipitation increases. Higher Intensities of precipitation during periods shorter than Tc can produce higher peak flows, even if not all area of the drainage basin contributes for the formation of the peak flow. The decrease of the intensity of precipitation with the time of transportation in the pipe sewers in the rational method may produce a larger decrease in the peak flow than the effects of propagation, attenuation and storage in the pipe sewers, as I demonstrated with a very simple example in the conference article from 1996 in attachment of my first answer. I confirmed those results also for tree-like networks (arborescent networks) in a more elaborated example that I developed on that time.

To delineate you can use google earth, it is helpful for make representative city from bird eyes. 

Dear Silvia: With respect to storm water everything is possible. It depends of the catchment areas and of the volumes of water that can be effectively collected. Harvesting of rain water can help (as pointed by Subba Rao). However, at first glance, it may seem a little romantic. The question is the percentage of permeable surfaces that can be effectively achieved. I suppose that the traditional idea of urbanism with many green spaces private and public, and with low areas of impermeable surfaces (garden cities) can be perhaps much more effective. Remember that all volumes of pluvial water in excess not retained in basins, natural or artificial flows superficially (see for example any book or chapter of urban hydrology or urban drainage).

@ Dear Dr. Telvari,

It's probably too late to answer, but go through this recently updated Q:

Dear Yang Pan,

I do have a few well calibrated models of small to medium sized urban drainage systems (including rainfall runoff). However I'm not sure wether this is what you are looking for.

best regards

Francois Clemens

The following links are some reports and projects about rainwater harvesting in Africa which can be of your interest:

I am not sure whether you have seen these example files or not. There is an application manual as well, you can learn SWMM while referring this. Although this application manual was for SWMM 5.0 but there is not much difference between 5.0 and 5.1. These example files will offer you some realistic data for learning.

Olivier,

Many thanks for the references. It sounds like there will be some uncertainities in the results...

Regards,

flow depth versus friction factor ..is quite correct as remarked by Mark, but I think the entrance conditions in your case i.e. the cross sectional area of flow may be not having a regular predefined regular shape, if it is a natural inflow condition over natural stream bed approaching towards culvert. One must be alert here , specifically natural ungauged scenarios, where whole flow (volume & discharge) is merely based on two uncertain entities 1. roughness (has many factors to get influenced in time and space domain during flows), 2. irregular shape to vary flow cross sectional areas in variety of way over time and space

Dr Gaur    

Hi. I think that within a decision matrix the decision variable should be energy gain with UA. This variable should be expressed as kW.hr-1 gained, Mega Joules, or kilocalories. The ratio between energy used by traditional agriculture per unit of area versus energy used by UA should be a good indicator of the goodness of the practice in urban areas. In this computations water plays a main role. Other way to view that is trying to answer the question: how many calories are invested for producing one calorie of some product? If the energy produced is higher than that invested then we may consider a good sustainable option.

This citation may be useful as well - 

@Nivedita,

If I understand your question well, Find the nearest similar cover type condition for bioretention area and extract the CN value from existing standard tables based on EXPERT ELICITATION/JUDGEMENT.

Appears safe and low for a stormwater discharge. Some literature suggest a trigger value of <5 mcg/L for aquaculture. Judging by your local standard and once discharged into the ocean (as a worse case scenario) the assimilation should be sufficient to keep the resulting level well below 1.3 mcg/L.

Dear Racha EL-OSMANI

Disks and Cartridges with C18 can be used but attention is required for pH adjustment. However variation of recovery is vary for SPE methods. I have used this for pesticide residue analysis.  

Bonded-phase silica (e.g., C18) will hydrolyze on prolonged exposure to aqueous

samples with pH levels of less than 2 or greater than 9. Hydrolysis will increase at the extremes of this pH range and with longer contact times. Hydrolysis may reduce extraction efficiency or cause baseline irregularities. Styrene divinylbenzene (SDB) extraction disks should be considered when hydrolysis is a problem (from METHOD 3535A)

SPE methods for Phthalate esters (METHOD 3535A,8061A

rgards

Piyal

reducing distribution losses, use of sewage water after treatment, dual water supply system (separate distribution systems for potable and grey water), installation of rainwater harvesting system in buildings, imple, implementation of  artificial recharge structures, construction of recharge trenches and pits along storm water drains etc.

Adham: Amount of rainfall will transform into Evapo-transpiration depends on so many factors (e.g. air temperature, types of plants, relative humidity, vapor pressure, soil moisture, geographical pattern, etc.). Similarly, amount of rainfall will transform into infiltration depends on many factors such as soil type, land use/ land cover, ground slope, etc.).

Therefore, Percental Prediction of Evapo-transpiration and Infiltration based on Rainfall Quantity or total water storage will certainly not give you accurate prediction for a particular watershed. If you have Field Measurement Data for Evapo-transpiration and Infiltration of a very similar characteristics Watershed (e.g. size, shape, slope, climatic condition, etc.) then only you may use Percental Prediction with Caution.

Using biological soil crusts to stabilise shifting sand dunes might be of interest. Biodiversity is increased and the hazard of shifting dunes and dust storms is reduced. E.g. http://www.nature.com/nchina/2014/140108/full/nchina.2013.132.html and follow through to original article in ES+T.

Genneraly BMPs located in the headwaters protect recipients from pollution accumulated in specific storm drains and BMPs located lower down in the watershed are used to remove pollutants accumulated in the whole watershed. It is hard to say anything more with no aditional data, it all depends on which BMPs are used and why, where your watershed is located (rural or urban area), what souces of pollution are there in the watershed..

the retention time can be correctly measured by the equation

HRT=nLWD/Q

n=porosity of the substrate, L=length of the cell, W= width of the cell, D= effective depth of the cell, Q= average flow rate of the wastewater.

Q (average)= (Average Inlet flow+Outlet flow)/2

Outlet flow can be measured by calculating the evapotranspiration rate of the constructed wetland.

For more details you can further contact to me.

It is clear that the standards of performance of discharges from urban stormwater conduits (either surface channels or underground pipes) vary with jurisdiction. In Ontario Canada the managment of urban runoff (stormwaters as well as low flows) is manages under a permitting system. The permits specify expected outcomes for a given system. Certain levels of water quality are expected and exceedances of these level are allowed on a frequency basis. Excessive excedances resuts in the issuance of a charge for pollution. The system works only moderately well at best. We are currently working hard to redevelop these stormwater systems to integrate on site retention of stormwater as much as possible reducing the volumes of stormwater and increasing the quality as well. The banning of the aesthetic use of pesticides has gone a longway to improving that aspect of water quality from urban areas. We need to do something regarding the use of fertilizers for green spaces.

There is also a strong movement to redesign urban stormwater systems to more natural channels engineered to handle the modified flow regimes and to increase assimilative capacity so that discharges to the natural (not engineered channels) is similar in both flow regime and water quality.