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Harvest Rainwater and Prevent Flooding

The City is being proactive by alerting Claremont property owners to avoid potential problems from flooding due to intense storms likely to result from El Nino. We also need to be proactive about the opportunities to harvest rainwater to mitigate effects of the prolonged drought. Let’s harvest rainwater and prevent flooding, while continuing to conserve water and save our trees which also help slow down rainfall.

Harvesting rainwater naturally deep-waters trees and shrubs that need more water to survive. It also helps replenish aquifers to supply wells Claremont depends upon for drinking water. In addition, harvesting rainwater reduces runoff to avoid overwhelming storm drain systems.

How can we harvest rainwater? Of course we can start with rain barrels at each downspout to collect water from our roof. It’s ideal for watering house plants. MWD is currently providing rebates for rain barrels. (See

We can collect much more water by thinking beyond the rain barrel. It does not take much work with a shovel to create tree wells around the drip line so more water will percolate into their root zones. Similarly, digging berms along contours catches water before it flows down slopes. (Small berms, are much like furrows from contour plowing.) Also dig micro dams to catch water at keylines (where the slope of flow lines change). If you liked playing in a sandbox, you will find this fun to do…children might enjoy doing it with you. Grandma and grandpa can do it too. Or, hire a gardener with a shovel. Digging tree wells, berms, and micro dams may cost less than installing rain barrels.

Harvest even more rainwater by contracting with a licensed landscape architect and landscape contractor to design and install bioswales, perforated drains, drywells, detention basins, cisterns, and roof gardens. Bioswales slow water flow and filter runoff. Perforated drains get water into the ground. Drywells increase percolation of captured rainwater. Detention basins hold water, reducing peak flows, and allow it to percolate. Cisterns store rain water underground or in walls. Roof gardens hold water on roofs and use it to irrigate protective plants. When creatively designed and implemented, any of these improvements can be woven into your garden adding value to your property, reducing your need to irrigate and providing protection from flooding. Good landscape makes our environment more pleasant by providing trees to intercept rainfall, shade our homes, and reduce heat island effects.

If each property owner would harvest rainwater that falls on their property, Claremont would have more water and lower risk of flooding. Take action now to help end drought conditions and also help protect yourself and your neighbors from flooding during storms that may be intensified by El Nino.

The MS4 Mandate requires that Claremont clean up runoff. One of the best ways to do this is to prevent runoff. And, the more water we percolate into the ground, the more water will be in the aquifer that feeds the wells which provide much of our drinking water. Wouldn’t it be nice to integrate green storm water infrastructure planning with the management of our potable water system?

Find out more about what Claremont is doing to harvest rainwater and prevent flooding at the Community Preparation Day November 21st. (See

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