SECTION 1

GENERAL INFORMATION Page 5

Introduction Page 5

Warning Systems Limitations Page 5

Flash Flood - Causes and Effects Page 6

General Procedures Page 7

SECTION II

ORGANIZATION Page 8

System Outline Page 8

Planning a System Page 9

Maps and Sources of Information Page 9

Identification of Flood-Prone Areas Page 9

Assistance from National Weather Service Page 10

Coordination of the System Page 10

Training Program Page 10

SECTION III

FORECASTING Page 10

Information Needed Page 11

Precipitation Consideration Page 11

Runoff Estimation Page 11

Rainfall Gauges Page 11

Rainfall Records Page 12

Stream Gauges Page 12

Flood Stage Time of Travel Consideration Page 12

Summary Page 13

SECTION IV

WARNING SYSTEM Page 13

Central Warning Point (Coordination Center) Page 13

Flood Warning Coordinator Page 13

Rainfall Observers Page 14

Stream Gauge Observers Page 14

Selection of Observers Page 15

Stream and Road Patrols Page 15

Effects of Warning Time Page 16

SECTION V

ALERTING SYSTEM Page 16

Communications Page 16

Emergency Operations Center Page 16

Public Information Page 17

Community Awareness Program Page 17

Emergency Information Page 17

SECTION VI

INFORMATION ANALYSIS SYSTEM Page 18

Analyzing - Decision Making Page 18

Role of Flood Warning Coordinator Page 19

SECTION VII

POST-FLOOD EVALUATION Page 20

Evaluation Process Page 20

System Continuity Page 20

SECTION VIII

TRAINING PROGRAM Page 21

General Page 21

Training Program Outline Page 21 County Flood Warning Coordinator Page 21

Rainfall Observers Page 22

Stream and Road Patrols Page 22

Stream Gauge Observers Page 23

ATTACHMENTS

A - Memorandum of Understanding Page 24

B – Categorical Forecast Graph Page 26

C - Installation, Operation and Maintenance of Rainfall Gauge Page 27

D - Instructions to Rainfall Observers Page 28

E - Flood Warning Tabulation Sheet Page 32

F - Criteria to Determine Need for a Stream Gauge Page 34

G - Procedures in a Site Survey Page 35

H – Installation of a Stream Gauge Page 37

I - Stream Gauge Maintenance Checklist Page 40

J - Stream Gauge Observation Work Sheet Page 41

K - Instructions to Stream Gauge Observers Page 42

L - Outline of Operational Procedures for Emergency Operations Center Page 42

M - Flooding Information of the Shenandoah River, Potomac River

And the Opequon Creek Page 45

N – Other Streams for Observers Page 53

O – Springs to be Observed to Cause Flooding Page 54

JEFFERSON COUNTY PLANNING GUIDE

FOR A COUNTY FLOOD WARNING SYSTEM

SECTION ONE

General Information

INTRODUCTION

Flash floods have doubled their destructiveness in the last twenty years and now rank first among weather-related disasters in the United States.

A recent example of flash flooding occurred in West Virginia in 1985. Historically, the Appalachia area has had a high frequency of flash floods. Narrow valleys, flanked by steep hillsides, produce fast overflows from heavy rains. It has been the increased use of these valleys that has caused such a dramatic upsurge in damage. The lure of these usually peaceful flood plains is likely to continue, and with it, the continued rise in the potential loss of life and property.

This planning guide for a County Flood Warning System was developed to assist in the establishing of local flood warning systems. The system as outlined herein is intended to complement, through voluntary help, the existing warning system of the National Weather Service.

The forecast programs outlined in this guide maximizes warning time since it is based primarily on rainfall rather than stream flow. With cooperation of the Jefferson County Office of Emergency Management and cooperation with the National Weather Service and the West Virginia Division of Homeland Security and Emergency Management, a flood warning system can be developed that will substantially reduce the threat to life and potential property damage from intense, highly localized rainstorms.

WARNING SYSTEM LIMITATIONS

There are limitations to the county flood warning system. Thunderstorms can produce intermittent rainfall with varying intensity; therefore, it is difficult to determine when the highest rates of runoff will occur, and when the flood crest might reach an area. There is also the possibility of having one, two or more flood crests during a flash floods situation.

Stream flows during a flash flood are unpredictable. A blocked bridge or culvert can divert or change water flow both upstream and downstream of where the blockage occurs. Rapid flood flows can create new channels and new directions of water flow. Recent developments, a new road, a new house, extensive logging or land clearance, and other construction can cause changes in water runoff behavior not previously experienced. Early observation of heavy rainfall, followed immediately by on-scene personnel to observe the effect of the rainfall runoff, is the only practical method of warning of potential flooding along small flashy streams.

Citizens who are voluntarily committing their time and property as a service to their community operate this program. Their obligation to fulfill their assigned functions does not rest upon any legally imposed duty, but upon a sense of moral obligation. Dangers are ever present in flooding situations and volunteers are not asked or expected to expose their lives or property to potential harm.

These comments about the limitations of a flood warning system are not intended to lessen the importance of such a system. They are mentioned to emphasize to the operators of this system and the general public that there are restraints, which must be considered.

There also should be a distinction made that this system does not replace National Weather Service flood warnings for the general area or for rivers and major tributary waterways in the area. The self-help flooding warning system is intended as supplement to other warning systems.

FLASH FLOODS - CAUSES AND EFFECTS

Flash floods are aptly described as the "Killer from the Hills." Flash flood waves, moving at incredible speeds, can roll boulders, tear out trees, destroy buildings and bridges, and scour out new channels. Killing walls of water can reach 10 to 20 feet.

Flash flooding is caused by interrelated factors: heavy rainfall; geological and topographic features which facilitate rapid runoff; and human development placed in surface runoff pathways. Property damage and loss of life have increased due mainly to the spread of residential and commercial development of land within the flood risk zones of small waterways.

Throughout much of West Virginia, the topography and geology within drainage areas is very conductive to flash flooding. Over much of the area, the land rises rather sharply from the valley floors into a series of rolling hills interspersed with narrow, steeply sloping valleys. This condition sets the stage for rapid runoff during periods of intense rainfall. Small streams quickly reach bank full stage, and with extended heavy precipitation, flood follows. Forest and other debris, much of which finds its way into stream courses, compounds the flooding problem by blocking narrow channels and man-made obstructions (culverts and bridges) and forces the water to higher stages, thereby increasing the area affected by flood flows.

Intensity and duration of rainfall are the key elements involved in flash flooding. Intensity is the rate of rainfall or how much rain a storm drops in a given period of time. Duration is how long a storm affects a given area.

Meteorological skills are low in forecasting the amount of rainfall and locations of centers of heavy rainfall. However, there is some skill in recognizing rather large areas in which some portions might receive heavy rain. This is not accurate enough for stream forecasting but can serve as an alerting mechanism - as is used in issuing a "Flash Flood Watch."

Flash floods can occur during any month but they are rare during the cold months. The frequency is greatest from May through September. On the average, July is the month of greatest flash flood activity in West Virginia.

Stationary or very slow moving thunderstorms are the usual flood producers. Faster moving storms that move in rapid succession over the same area can also produce the volume of rain necessary to cause flash flooding. Taking into account the innumerable possibilities of rainstorms in terms of: intensity and duration of rainfall; the variability of physical features between watersheds; the limitations of the existing flood warning system; and the inherent short warning time with flash flooding; a program of voluntary, local rainfall observation and rapid action is the best means of providing an effective warning to residents and developments along small streams.

GENERAL PROCEDURES

The following are general procedural steps in establishing the Jefferson County Flood Warning System:

1. National Weather Service briefs Jefferson County Office of Emergency Management Director on the development of Flood Warning System.

2. Jefferson County Office of Emergency Management signs Memorandum of Understanding (MOU) for Flood Warning System and forwards to National Weather Service.

3. Jefferson County Office of Emergency Management identifies observation points that are staffed around the clock and volunteers who are willing to participate in the program by making rainfall observations and reports (police headquarters, fire houses, hospitals, industrial plants, etc.).

4. Jefferson County Office of Emergency Management Director designates a County Flood Warning Coordinator.

5. County Flood Warning Coordinator identifies, on stream map, those locations where flooding has occurred in the past and sites of possible future flooding.

6. National Weather Service reviews with the County Flood Warning Coordinator locations of proposed rain and stream gauges. National Weather Service determines need for remote reporting gauges.

7. Based on 5 and 6 above, the County Flood Warning Coordinator recruits volunteer rainfall observers and stream gauge observers.

8. National Weather Service and the Jefferson County Office of Emergency Management will provide gauges.

9. Jefferson County Office of Emergency Management will install stream gauges and distributes rain gauges.

10. National Weather Service and Jefferson County Office of Emergency Management will conduct training for the County Flood Warning Coordinator and all observers. Advises on establishing:

a. Alerting system (communications);

b. Record keeping system;

c. Information analysis system;

d. Reporting system; and

e. Warning system.

SECTION TWO

Organization

SYSTEM OUTLINE

The Jefferson County Flood Warning System, to be successful, will require establishing an organization that includes functions and elements as outlined below:

1. A County Flood Warning Coordinator is a volunteer member of the Office of Emergency Management staff.

2. Detailed mapping of flood-prone areas to identify areas that have high flood susceptibility.

3. Coordination of all existing emergency radio systems.

4. Volunteer stream gauge and rainfall observers.

5. An information exchange system between National Weather Service and the County Flood Warning Coordinator.

6. An alerting and mobilization system for rainfall and stream gauge observers.

7. A prearranged system for rainfall and stream gauge observers to alert the coordinator.

8. An information analysis system to evaluate possible flood conditions.

9. A record keeping system to record rainfall and stream gauge readings during each storm.

10. An alerting system, which provides methods for the coordinator to communicate to, prearranged locations; flash flood watches, flash flood warnings, flood predictions and evacuation warnings.

11. Emergency communications systems.

12. Emergency action procedures organized to respond to the flood warning system to include stream and road patrols and evacuation.

PLANNING THE SYSTEM

The following steps are to be taken by the Jefferson County Flood Warning Coordinator in the organization of a flood warning system:

1. Maps and Sources of Information

a. A map of the county which shows streams, water courses and the road system will be needed to begin the planning of the system. Most county highway maps meet this need. Other maps that are useful for study and planning are as follows:

(1) State Gazetteer of Streams.

(2) U.S. Geological Survey contour quadrangle maps for study in detail.

(3) Aerial photos at various scales for additional detailed study.

(4) Detailed flood plain maps are available for communities participating in the Flood Insurance Program (NFIP). This shows the floodway and 50 to 100 year flood contours.

b. There are other sources of information, which may be useful in organizing the system.

(1) Corps of Engineers studies and projects.

(2) Soil Conservation Service studies or projects. (Check with the County Soil and Water Conservation Office).

(3) National Weather Service records and studies.

2. Identification of Flood-Prone Areas

The next step in the organization of the system is the identification of points or areas, which are subject to flash flooding. Mark areas or point on the county map where flash flooding has occurred in the past. Make a list with the name of the stream, and the locations of the areas or communities that have had flash flood damage, they identify the locations along these streams where substantial damage has occurred in the past.

A record of the number of homes or kind of damage that occurred should be added if available. If available a list of the number of times and dates that streams have flooded would also be valuable. Identify where there are steep watersheds or streams and areas where development has occurred in low-lying areas where flash flooding is possible. Remember that just because an area has not had a flash flood does not mean it will never have one.

Changes in land use, relocation of roads; new residential and commercial development may be located within the flood risk zones of small waterways.

3. Assistance from National Weather Services

The first step in obtaining assistance from the National Weather Service is signing the Memorandum of Understanding (MOU) between the county and the National Weather Service (see Attachment “A”). This agreement establishes a working arrangement whereby the National Weather Service can provide assistance and the county in turn agrees to operate a flood warning system. After the initiation of the memorandum, a representative from the National Weather Service will visit the county to make recommendations for the installation of the necessary equipment and provide technical flood warning procedures.

4. Coordination of the System

The key person in the operation of the flood warning system is the coordinator. The Office of Emergency Management Director may wish to delegate someone to act as the coordinator for the system but should still assume overall responsibility and authority for the operation of the system. The coordinator should know what to do to initiate warning and action systems at the county and community level. (See Section IV and V).

5. Training Program

A training program for the participants in the flood warning system should be developed to insure understanding of how the system is to operate. Inspection and training exercises of the system should be held at least once each year.

SECTION III

Forecasting System

INFORMATION NEEDED

The following types of information are used in the Jefferson County Flood Warning System for each storm or flood situation:

1. Precipitation (rainfall, snowfall, sleet, etc.) as measured by rain gauges.

a. Total amounts during a storm.

b. Intensity or rate of accumulation.

c. Snow cover and the rate of melting.

2. Precipitation runoff.

3. Stream height as measured at stream gauges.

4. Time of travel of flood crests.

5. Time of crest in hours after end of heavy rain.

All of this information must be considered to develop a flood forecasting procedure and must be available in order to provide flood warnings. Most watersheds have such a variable pattern of rainfall during a flood that only estimations of actual stream flows are possible. Collection of data over many years will permit more accurate predictions.

PRECIPITATION CONSIDERATION

Several factors are considered in evaluating the effects of precipitation in each storm. These include: the form of the precipitation such as rain, snow or sleet. The most important parameter to consider in evaluating the effects of a storm is the total rainfall. Snow cover can have two opposite effects - if it is deep and very cold, it can decrease the runoff by freezing the rain and holding it in the snow pack - if the snow is melting, it will add liquid water to the rain and increase the stream flow. The National Weather Service should be consulted when snow cover is present during a rainstorm.

RUNOFF ESTIMATION

The National Weather Service River Forecasting Center (Harrisburg, PA) monitors many factors which are used to estimate the amount of rainfall that is infiltrating or soaking into the soil and Index (See Attachment “B”). This Index can be used by the County Flood Warning Coordinator to interpret observed rainfall in the watershed and then estimate the amount of runoff and stream levels.

RAINFALL GAUGES

A network of manned rainfall observation stations must be established to monitor precipitation in the county. Each station must be provided with a rain gauge for making observations. The National Weather Service should make selection of these observer stations following review. They should be located so that they can provide observations of rainfall in each of the problem watersheds in the county. Wherever possible, there should be rainfall observation stations located at public facilities where 24-hour surveillance is possible. Instructions for installation, operation and maintenance of rainfall gauges are shown at Attachment “C”.

RAINFALL RECORDS

Each rainfall observer should record rainfall amounts daily. During periods of heavy rainfall, accumulations should be observed more often. They may require making observations as frequently as once an hour or less. The intensity and duration of rainfall determines flash flood conditions, therefore, frequent and timely observations and reporting during a storm are important.

Instructions for recording observations are contained at Attachment “D”. A sample flood warning computation sheet is shown at Attachment “E”. A documentation sheet would be filled out when the rain gauge observers started calling in.

STREAM GAUGES

Criteria for determining the need for stream gauges are outlined at Attachment “F”. Stream gauges are normally placed at several locations in a watershed. These gauges are placed along the major tributary streams, often above and below the junction of two streams, in major flood-prone areas, and in areas that will increase understanding of water movement of the entire stream system. Procedures to follow during a site survey to determine location of stream gauges are outlined at Attachment “G”.

A series of stream gauges up and down a river provide a linking record of what happens during a particular storm. By using several gauges, the relationship between recorded rainfall and the runoff amounts for each tributary or segment of the stream can be established. Careful observation of how rapidly the stream increases its flow or stage height with a given amount of rainfall is used to make future flood stage predictions. A sample care and maintenance checklist for stream gauges is at Attachment “I”.

FLOOD STAGE TIME OF TRAVEL CONSIDERATION

Observations of several stream gauges along a stream or watershed provide a means of estimating the average time it will take for a flood crest or maximum flood level to travel down the stream. This is usually complicated by the fact that no two storms are exactly alike. A particular tributary may receive more rain or may have more rapid runoff with respect to the rest of the watershed in different storms. Therefore, records are maintained over a period of years. Attachment J is a sample Stream Gauge Worksheet and Attachment ”K” contains instructions for Stream Gauge Observers. From this recorded history, increasingly accurate predictions can be made for the time of travel of the flood stage.

SUMMARY

Assembling all of the information on rainfall duration and intensity, rainfall/runoff conditions, stream gauge measurements, flood crest time of travel, and maintaining records of this information provides the basis for the county flood warning system. This data is assembled into tables, which will make it possible for an organized flood warning system to operate.

SECTION IV

Warning System

CENTRAL WARNING POINT

The Jefferson County Emergency Communications Center will be the primary County Warning Point and the West Virginia State Police – Troop 2 Communications Center will the alternate County Warning Point which both are manned 24/7, where all rainfall reports can be initially received. Personnel at the Emergency Communications Center or State Police will be knowledgeable of the conditions under which they notify the County Flood Warning Coordinator who will then operate the flood warning system.

COUNTY FLOOD WARNING COORDINATOR

The County Flood Warning Coordinator is the focal point for the flood warning system. Rapid preplanned action will be needed to make the flood warning system operate successfully and accomplish what is designed to do - to reduce the threat to the general public of flooding and flood damage.

There should be a backup person who is trained to operate the system in case the coordinator is not available for any reason. There should be an assigned order of succession of these backup persons so that each knows when they are responsible to assume their role.

Specific tasks of the Jefferson County Flood Warning Coordinator or backup persons are:

1. Directs and coordinates the continuous operation of the Jefferson County Flood Warning Program.

2. Develops standard operating procedures for the operation of the flood program.

3. Recruits, organizes and trains rainfall observers, stream gauge observers.

TABLE OF CONTENTS